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Introduction

When temporary mechanical ventilation is required either in the treatment of respiratory failure or during surgery with muscular

relaxation endotracheal intubation is usually the preferred method of airway management

Why is this the preferred means of airway management The primary reason is that it provides a protected airway

Protected from what you ask

Well protected from introduction of foreign matter particularly gastric contents

The accurate placement of an endotracheal tube requires skill Usually the patient is rendered unconscious and immobile (including

paralysis of the muscles of respiration) for the placement Obviously inability to rapidly obtain control of the patients airway in this

setting would be bad if not lethal

The airway examination is an effort to identify those patients in whom conventional endotracheal intubation will be difficult It is vitally important to recognize such patients BEFORE administering medications that induce apnea( Lack of breathing)

Endotracheal Intubation

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Endotracheal Tube

Acknowledgements

This educational site was developed by

Tammy Euliano MD Associate Professor of Anesthesiology

with the assistance of

future doctor Amy Lee programmers Karthik Paladugu and Rick Lockwood graphic artist future doctor Christopher Hurt

Major contributions were provided by

Ilona Schmalfuss MD Assistant Professor of Radiology Jeremy Melker MD Otolaryngology Resident

Funding was provided by the

University of Florida College of Medicine Education Committee

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Aspiration of Gastric Contents

The risk of passive reflux of gastric contents into the pharynx is increased when the stomach is full If the gag reflex has been

blunted (by alcohol ingestion decreased mental status or medications) the acidic volume can make its way into the trachea

causing potentially extensive damage

Aspiration Prevention

In this case which of the following could reduce the risk of

aspiration and its consequences

Wait 6 hours before proceeding keeping the patient NPO

Yes No

(yes) Incorrect - Nil per os

While this will help for elective surgery patients trauma patients and

those with acute GI problems will not empty their stomachs well In

addition this operation should not be postponed for any length of time due to the risk of appendix rupture andor sepsis

(no)Correct

While a 6-hour NPO period is ideal this surgery should not be

postponed

Administration of a non-particulate antacid

Yes No

(yes)Correct - Non-particulate antacid

Many would advocate having the patient drink 15-30cc sodium citrate or bicitra within 30 minutes of induction of anesthesia

Though this increases the stomach volume it is actually protective

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as it raises the pH of the stomach contents reducing injury to the

lung in the event of an aspiration

(no)Incorrect - Non-particulate antacid

Many would advocate having the patient drink 15-30cc sodium citrate or bicitra within 30 minutes of induction of anesthesia

Though this increases the stomach volume it is actually protective as it raises the pH of the stomach contents reducing injury to the

lung in the event of an aspiration

Administration of H2 blockers

Yes No

(yes)Correct - H2 Blockers

The onset time of these medications is 30+ minutes and even then they do not affect the pH of the volume already in the stomach

However new fluid will be secreted into the stomach at a higher pH perhaps increasing the overall pH by the time of emergence from

anesthesia (the other time at which patients are at risk for aspiration)

(no)Incorrect - H2 Blockers

The onset time of these medications is 30+ minutes and even then they do not affect the pH of the volume already in the stomach

However new fluid will be secreted into the stomach at a higher pH perhaps increasing the overall pH by the time of emergence from

anesthesia (the other time at which patients are at risk for aspiration)

Administration of metoclopramide

Yes No

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(yes)Correct - Metoclopramide

Metoclopramide speeds gastric emptying and increases the lower

esophageal sphincter (LES) pressure While the latter is helpful at reducing the risk of aspiration within minutes stomach volume

reduction takes more time This emptying should occur however

and can reduce the risk of aspiration during emergence and extubation at the end of the operation There are some risks to

metoclopramide so as with everything a riskbenefit evaluation must be performed

(no)Incorrect - Metoclopramide

Metoclopramide speeds gastric emptying and increases the lower esophageal sphincter (LES) pressure While the latter is helpful at

reducing the risk of aspiration within minutes stomach volume reduction takes more time This emptying should occur however

and can reduce the risk of aspiration during emergence and extubation at the end of the operation There are some risks to

metoclopramide so as with everything a riskbenefit evaluation must be performed

Rapid Sequence Induction

Yes No

(yes)Correct - Rapid Sequence Induction

Following pre-oxygenation the patient is put to sleep with a rapid acting IV induction agent such as sodium thiopental immediately

followed by succinylcholine (or other rapid-acting agent) application of cricoid pressure and intubation of the trachea

Positive pressure mask ventilation is not performed to avoid increasing gastric volume The purpose of this technique is to

minimize the duration of impaired gag reflex prior to intubation

Cricoid Pressure during intubation

Yes No

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(no) Incorrect - Cricoid Pressure during Intubation

An assistant identifies the cricoid ring and applies pressure compressing the esophagus against the underlying vertebral

body This prevents passive reflux of gastric contents into the lung How much pressure to apply is a continuing question

current recommendations suggest approximately 10 Newtons (1 kg) of force (mild discomfort for the patient) as the induction

medications are being administered Once the patient loses consciousness the cricoid pressure should be increased to

approximately 30 Newtons (3 kg) It is possible for this pressure to make intubation more difficult and some reduction in force

may be necessary

(yes)Correct - Cricoid Pressure during Intubation

An assistant identifies the cricoid ring and applies pressure compressing the esophagus against the underlying vertebral

body This prevents passive reflux of gastric contents into the lung How much pressure to apply is a continuing question

current recommendations suggest approximately 10 Newtons (1 kg) of force (mild discomfort for the patient) as the induction

medications are being administered Once the patient loses consciousness the cricoid pressure should be increased to

approximately 30 Newtons (3 kg) It is possible for this pressure to make intubation more difficult and some reduction in force

Endotracheal Intubation

Intubation is typically performed under direct visualization That is

by looking through the mouth directly at the vocal cords (direct laryngoscopy) and watching the endotracheal tube pass through the

cords and into the trachea However there is no direct line-of-sight from the mouth to the vocal cords

Check in a mirror or examine a friend (preferably one who has not

eaten onions recently) even with the mouth maximally opened and

tongue extended you cannot see the vocal cords in fact only rarely can you see the epiglottis

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Mallampati Classification

Actually the amount of the posterior pharynx you can visualize is

important and correlates with the difficulty of intubation

Visualization of the pharynx is obscured by a large tongue (relative to the size of the mouth) which also interferes with visualization of

the larynx on laryngoscopy The Mallampati Classification is based on the structures visualized with maximal mouth opening and tongue

protrusion in the sitting position (originally described without phonation but others have suggested minimum Mallampati

Classification with or without phonation best correlates with intubation difficulty)

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Class I soft palate fauces uvula pillars Class II soft palate fauces portion of uvula

Class III soft palate base of uvula Class IV hard palate only

Other Predictors of Difficult Intubation

Obesity ndash body weight gt 110kg

Mouth opening ndash inter-incisor distance lt 4cm in an adult

Ability to prognath ndash a large overbite or the inability to shift

the lower incisors in front of the upper incisors

Thyromental distance ndash The distance from the thyroid cartilage to the mentum (tip of the chin) should be gt 65-7 cm

Mentum-Hyoid distance ndash Similar to thyromental distance and should be at least 3-4 finger-breadths

Many other factors have been investigated with variable results

Other factors that may indicate a difficult intubation

Sternomental distance ndash Similar to above measured from the sternum to the tip of the mandible with the head extended This measure is influenced by neck extension Should be gt125cm

Mandibulohyoid distance ndash the vertical distance between the mandible and the hyoid bone determined radiographically This may be increased with a short mandibular ramus or a caudally located hyoid bone Such an increase in this distance may be associated with difficult intubation Chou 1993

Thyrosternal distance ndash lt8cm may suggest difficulty probably related to the caudally located hyoid as above

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Mallampati Classification

Actually the amount of the posterior pharynx you can visualize is

important and correlates with the difficulty of intubation

Visualization of the pharynx is obscured by a large tongue (relative to the size of the mouth) which also interferes with visualization of

the larynx on laryngoscopy The Mallampati Classification is based on the structures visualized with maximal mouth opening and tongue

protrusion in the sitting position (originally described without phonation but others have suggested minimum Mallampati

Classification with or without phonation best correlates with intubation difficulty)

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Class I soft palate fauces uvula pillars Class II soft palate fauces portion of uvula

Class III soft palate base of uvula Class IV hard palate only

Other Predictors of Difficult Intubation

Obesity ndash body weight gt 110kg

Mouth opening ndash inter-incisor distance lt 4cm in an adult

Ability to prognath ndash a large overbite or the inability to shift

the lower incisors in front of the upper incisors

Thyromental distance ndash The distance from the thyroid cartilage to the mentum (tip of the chin) should be gt 65-7 cm

Mentum-Hyoid distance ndash Similar to thyromental distance and should be at least 3-4 finger-breadths

Many other factors have been investigated with variable results

Other factors that may indicate a difficult intubation

Sternomental distance ndash Similar to above measured from the sternum to the tip of the mandible with the head extended This measure is influenced by neck extension Should be gt125cm

Mandibulohyoid distance ndash the vertical distance between the mandible and the hyoid bone determined radiographically This may be increased with a short mandibular ramus or a caudally located hyoid bone Such an increase in this distance may be associated with difficult intubation Chou 1993

Thyrosternal distance ndash lt8cm may suggest difficulty probably related to the caudally located hyoid as above

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Class I soft palate fauces uvula pillars Class II soft palate fauces portion of uvula

Class III soft palate base of uvula Class IV hard palate only

Other Predictors of Difficult Intubation

Obesity ndash body weight gt 110kg

Mouth opening ndash inter-incisor distance lt 4cm in an adult

Ability to prognath ndash a large overbite or the inability to shift

the lower incisors in front of the upper incisors

Thyromental distance ndash The distance from the thyroid cartilage to the mentum (tip of the chin) should be gt 65-7 cm

Mentum-Hyoid distance ndash Similar to thyromental distance and should be at least 3-4 finger-breadths

Many other factors have been investigated with variable results

Other factors that may indicate a difficult intubation

Sternomental distance ndash Similar to above measured from the sternum to the tip of the mandible with the head extended This measure is influenced by neck extension Should be gt125cm

Mandibulohyoid distance ndash the vertical distance between the mandible and the hyoid bone determined radiographically This may be increased with a short mandibular ramus or a caudally located hyoid bone Such an increase in this distance may be associated with difficult intubation Chou 1993

Thyrosternal distance ndash lt8cm may suggest difficulty probably related to the caudally located hyoid as above

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Various radiographic measurements of the cervical spine its alignment with airway structures and the atlanto-occipital joint

Positioning

To obtain a direct line of sight the patient is positioned in the sniffing position The neck is flexed at the lower cervical spine and

extended at the atlanto-occipital joint This flexion and extension is amplified during laryngoscopy

The patientrsquos neck mobility should be assessed preoperatively by

having them flex and extend their head maximally The range of

motion should be more than 90deg Motion less than 80deg may triple the risk of a poor view at laryngoscopy

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Direct Laryngoscopy

Then a laryngoscope is used to pull the lower jaw and tongue up and out of the way

The metal blade is passed into the mouth to the level of the epiglottis then with an anterior and caudad motion (ie toward the

edge of the ceiling across the room) the lower jaw is elevated allowing visualization of the glottic structures( The glottis is the

structures of phonation including the vocal cords and surrounding structures) In most patients this results in a clear view of the larynx

and the endotracheal tube is passed through the vocal cords under

direct visualization

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Direct Laryngoscopy

Then a laryngoscope is used to pull the lower jaw and tongue up and out of the way

The metal blade is passed into the mouth to the level of the epiglottis then with an anterior and caudad motion (ie toward the

edge of the ceiling across the room) the lower jaw is elevated allowing visualization of the glottic structures( The glottis is the

structures of phonation including the vocal cords and surrounding structures) In most patients this results in a clear view of the larynx

and the endotracheal tube is passed through the vocal cords under

direct visualization

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Laryngoscopy Grades

In most patients Direct Laryngoscopy results in a clear view of the larynx The laryngeal view has been classified by Cormack and

Lehane as follows

Grade 1 Full view of the glottis Grade 2 Only the posterior commissure is visible

Grade 3 Only the epiglottis is seen Grade 4 No epiglottis or glottis structure visible

Airway Review

What might make Direct Laryngoscopy and Intubation more difficult

Inability to open the mouth

Yes No

(yes)Correct

There must be room to place the laryngoscope in the mouthhellipusually

at least 3 finger breadths in the adult

(no)Incorrect

There must be room to place the laryngoscope in the mouthhellipusually

at least 3 finger breadths in the adult

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Inability to extend the neck

Yes No

(yes)Correct

The sniffing position requires significant neck extension

(no)Incorrect

The sniffing position requires significant neck extension

Inability to breathe through the nose

Yes No

(no)Correct

Unless a nasal intubation is planned

(yes)Incorrect

Unless a nasal intubation is planned

Large tongue

Yes No

(yes)Correct

Also if it is immobile as from radiation therapy

(no)Incorrect

Also if it is immobile as from radiation therapy

Redundant pharyngeal tissue

Yes No

(yes)Correct

This occurs with obesity and is often suggested by a history of

snoring andor obstructive sleep apnea

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(no)Incorrect

This occurs with obesity and is often suggested by a history of snoring andor obstructive sleep apnea

Case 2 Abnormal Exam

A healthy 25-year-old man is scheduled to have a shoulder repair requiring general anesthesia

Lets review his airway examination

What would you like the patient to do

Open his mouth as wide as possible

Extend his neck as far as possible without pain

View from the side

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Open Mouth

This patients mouth opening is 2 finger-breadths the soft palate is

barely visible on maximal mouth opening

Neck

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View from the side

2 finger-breadths fit between the tip of the chin and the neck

Airway Examination

Mouth opening

Normal

Reduced

What is mouth opening

(normal)Incorrect

it is less than 3 finger breadths

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(reduced)Correct

The mouth opening is less than 3 finger-breadths

Open Mouth

The inter-incisor distance on maximal mouth opening Should be gt4 cm in an adult or 3-4 of the patients finger-breadths

This patients mouth opening is 2 finger breadths the soft palate is barely visible on maximal mouth opening

Mallampati Score

I

II

III

IV

What is Mallampati Score

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(I)Incorrect

The uvula cannot be seen

(II)Incorrect

Not even the top of the uvula is visible

(III)Yes

All structures visible up to the soft palate is a Mallampati Class III

(IV)Incorrect

The soft palate is visible

Mentum-Hyoid distance

Normal

Reduced

What distance

(normal)Incorrect

3 finger-breadths is normal this patient has only 2

(reduced)Yes

this is less than the normal 3 finger-breadths

View from the side

2 finger-breadths fit between the tip of the chin and the neck

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Neck Extension

Normal

Reduced

What is neck extension

(normal)Correct

The neck extends

(reduced)Incorrect

The neck motion is gt 90 degrees

Neck

The range of motion should be more than 90deg Motion less than 80deg may triple the risk

of a poor view at laryngoscopy

Airway Evaluation Summary

Because of the reduced mentum-hyoid distance it may be difficult to visualize the larynx with traditional direct laryngoscopy There are

other options including other blades and techniques that do not require a direct line-of-sight which are beyond the scope of this site

Perhaps the most conservative method of securing the airway of a

patient who is anticipated to have a difficult airway is with awake

fiberoptic intubation This technique requires substantial skill but allows intubation in an awake spontaneously breathing patient The

trachea is identified with a flexible fiberscope and then the endotracheal tube is advanced over the fiberscope like a stylet Such

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a procedure requires blockade of the sensory innervation to the

airway and blunting of the gag reflex

Innervation of the Upper Airway

Awake fiberoptic intubation requires topical anesthesia for patient

comfort as well as to blunt the gag reflex that would prevent successful intubation of the trachea

Several nerves are involved in the sensation of the upper airway

Anterior 23 of the tongue - Trigeminal nerve (V)

Posterior 13 of tongue to epiglottis - Glossopharyngeal nerve (IX afferent limb of gag reflex)

Epiglottis to vocal cords - Internal branch of Superior Laryngeal Nerve (Vagus X)

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Trachea below vocal cords - Recurrent Laryngeal Nerve

(Vagus X)

MOTOR INNERVATION

Motor innervation to the larynx is provided by the Vagus Nerve but recall there are two branches involved The Recurrent Laryngeal

Nerve innervates all the muscles of the larynx EXCEPT the

cricothyroid muscle which is innervated by the External Branch of the Superior Laryngeal Nerve Because the function of the

cricothyroid muscle is to stretch and tense the vocal cords unopposed action of the cricothyroid as may occur with bilateral

destruction of the recurrent laryngeal nerves would lead to stridor respiratory distress and possibly airway obstruction

GAG REFLEX

So the sensory afferent limb of the gag reflex is the glossopharyngeal nerve (IX) while the motor efferent limb is the

Vagus (X)

Its not much of a mnemonic but I remember this as a variant of TGIF Thank God its Recurrent I know its lame perhaps just

lame enough to be memorable

Airway Blocks

Topical application of local anesthetics is usually sufficient for the tongue and oronasopharynx though glossopharyngeal blocks are

performed occasionally Blunting of the gag reflex requires Transtracheal (really translaryngeal) with or without bilateral

Superior Laryngeal Nerve blocks as shown below

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The superior laryngeal nerves are blocked by deposition of 1 lidocaine near where the nerves penetrate the thyrohyoid

membrane The transtracheal block is accomplished with 4 lidocaine injected directly into the tracheal lumen Often this block

alone coupled with nebulized or atomized lidocaine is sufficient for awake intubation

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Airway Structures

The right panel displays images seen during fiberoptic bronchoscopy The corresponding level on CT is displayed on the middle panel

Place the cursor over structures to learn their identity

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Review of Airway Innervation

Lets review the innervation of the upper airway

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Purple

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(V)Yes

The maxillary branch (V2) supplies the nasal cavity and palate while the mandibular branch (V3) supplies the anterior 23 of the tongue

(IX)Incorrect

The glossopharyngeal nerve supplies sensation to the posterior 13

of the tongue and its overlying structures including the soft palate

(X)No

The vagus innervates the airway further distal

Green

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)Yes

The glossopharyngeal nerve supplies sensation to the posterior 13

of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(X)No

The vagus innervates the airway further distal

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Blue

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)No

The glossopharyngeal nerve supplies sensation to the posterior 13 of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(x)Yes but which branch

Internal branch of superior laryngeal

External branch of superior laryngeal

Recurrent laryngeal

(Yes

The Internal Branch of the Superior Laryngeal Nerve provides

sensory innervation to the mucous membrane from the epiglottis to

and including the vocal cords

Incorrect

The External Branch of the Superior Laryngeal nerve provides motor innervation to the cricothyroid muscle only

Incorrect

The Recurrent Laryngeal Nerve supplies sensory innervation to the

trachea below the vocal cords as well as motor innervation to all the

intrinsic muscles of the larynx except the cricothyroid muscle)

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Red

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)No

The glossopharyngeal nerve supplies sensation to the posterior 13 of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(x)Yes but which branch

Internal branch of superior laryngeal

External branch of superior laryngeal

Recurrent laryngeal

(Incorrect

The Internal Branch of the Superior Laryngeal Nerve provides sensory innervation to the mucous membrane from the epiglottis to

and including the vocal cords

Incorrect

The External Branch of the Superior Laryngeal nerve provides motor innervation to the cricothyroid muscle only

Yes

The Recurrent Laryngeal Nerve supplies sensory innervation to the

trachea below the vocal cords as well as motor innervation to all the

intrinsic muscles of the larynx except the cricothyroid muscle)

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Case 3 Spine Evaluation

A previously healthy 40-year-old male presents with an open femur fracture from a Motor Vehicle Accident (MVA) that needs to be

repaired under general anesthesia He is currently on a backboard

with a cervical collar in place and is hemodynamically stable

Examination of this patients airway is complicated by the presence of the cervical collar which both inhibits mouth opening and by

definition prevents neck extension As you have seen above neck extension is required for direct laryngoscopy

So what shall we do

Remove the neck collar and intubate as usual

Intubate with a technique that does not require neck movement

Avoid general anesthesia and perform a regional block for the

procedure

Perform studies to clear the cervical spine

First a basic review of the anatomy is helpful

Recall that the cervical spine consists of 7 vertebrae the first two of

which are highly specialized

(Should this patient have an unstable cervical spine the movement resulting from laryngoscopy could permanently damage the spinal

cord likely resulting in quadriplegia)

(There are numerous techniques (retrograde intubationhellip) purported

to involve less cervical spine motion each of which requires substantial skill and experience These should only be attempted by

experienced practitioners Some advocate in-line stabilization where a second person attempts to hold the cervical spine still while

the primary person attempts direct laryngoscopy This technique makes intubation more difficult and is inadequate for stabilization)

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Page 29 432012

(While an attractive option many would argue that anytime a

regional anesthetic is planned immediate endotracheal intubation must be possible Complications may occur during the regional block

or it may be inadequate for the operation or wear off before the surgeons are done Therefore inability to emergently intubate a

patient is a relative contraindication to regional anesthesia and should be considered in this patient with a possible unstable neck)

(Great idea)

Cervical Spine Anatomy-Atlas

C1 The Atlas is a ring that interacts with the skull base above and

C2 shown on next page It is unique in that it lacks a vertebral body and spinous process The articulation of C1 with the occiput is very

tight providing little of the flexion of the cervical spine and only about 20 degrees of extension

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Cervical Spine Anatomy-Axis

C2 The Axis has an unusual thumb-like extension of its vertebral body that passes through the arch of C1 This process is called the

dens or odontoid The odontoid process is normally held very tightly against the anterior arch of C1 by the transverse ligament

Meanwhile the spinal cord travels behind the odontoid within the

arch of C1

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Atlanto Axial Joint

This atlanto-axial joint provides the majority of the rotational motion of the cervical spine Meanwhile flexion and extension are primarily

accomplished at C2 and below and particularly between C4 and C6

Neck Movement with DL

What happens to the neck during direct laryngoscopy and

intubation

As you have seen the sniffing position involves neck flexion in the lower cervical spine with extension superiorly In the process of

direct laryngoscopy this motion is accentuated As the laryngoscope

is lifted upward the occiput is extended primarily at the atlanto-occipital joint (occiput-C1) while flexion occurs at C2-3 and below

Therefore any intervention that impedes this flexion and extension

will make visualization of the glottis more difficult In someone with a cervical fusion up to the occiput it is pretty much impossible to

perform direct laryngoscopy Similarly a patient with external stabilization such as a c-collar in this case will (SHOULD) have neck

movement reduced sufficient to make visualization difficult if not impossible

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Clearing the C-Spine

How does one rule out damage to the cervical spine

At present history is our greatest ally If the healthy patient has no history of neck problems and no symptoms on maximal flexion and

extension they are unlikely to have cervical spine disease

On the other hand there are many patients whose cervical spine

SHOULD be radiographically evaluated pre-operatively including certain trauma patients as well as those with disease states that

affect the cervical spine including rheumatoid arthritis and Downs Syndrome These diseases may affect the transverse ligament and

thus the stability at the atlanto-axial joint

Nexus Criteria

Which trauma patients require cervical spine films prior to surgery or

intubation There is a set of criteria identified by the National Emergency X-

Radiography Utilization Study (NEXUS) that attempt to identify patients with a low probability of injury thereby reducing the

number of negative cervical spine radiographs taken

The criteria include No midline cervical tenderness

No focal neurologic deficit

Normal alertness

No intoxication

No painful distracting injury that might make them ignore their

neck pain

For those patients whose cervical spine is not cleared the

anesthesiologist must consider the risks of cervical spine damage that can be worsened through direct laryngoscopy versus the risk of

alternative techniques that may minimize neck motion including awake fiberoptic intubation A description of these alternate

techniques is beyond the scope of this site at present

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Spine Film

For the current case the following film is obtained

Patients Film

Normal for Comparison

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Explanation

Note the large step-off between C6 and C7 This subluxation causes entrapment of the spinal cord and damage

Therefore this patient requires an intubation technique with minimal neck motion and awake positioningas well as some external

stabilization or operative intervention to prevent damage to the spinal cord at the neck

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C-Spine Review

So which patients are at higher risk for neck injury during intubation

Trauma patients

Yes No

(yes)Correct

They may have trauma to the cervical spine as well

(no)Incorrect

They may have trauma to the cervical spine as well

Rheumatoid arthritis patients

Yes No

(yes)Correct

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

(no)Incorrect

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

Downs Syndrome patients

Yes No

(yes)Correct

About 15 of these patients have laxity in the transverse ligament

that holds the odontoid against the anterior arch of C1 Xrays are also recommended in these patients prior to anticipated neck

manipulation including laryngoscopy

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Page 36 432012

(no)Incorrect

About 15 of these patients have laxity in the transverse ligament that holds the odontoid against the anterior arch of C1 Xrays are

also recommended in these patients prior to anticipated neck manipulation including laryngoscopy

Osteoarthritic patients

Yes No

(yes)Incorrect

They are not at higher risk

(no)Correct

They are not at higher risk

Patient with a prior cervical spine fusion

Yes No

(yes)Incorrect

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

(no)Correct

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

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Airway References

Cricoid Pressure

Vanner RG Asai T Safe use of cricoid pressure Anaesthesia 1999 54 1-3 A review of literature with recommendations

Sellick BA Cricoid pressure to control regurgitation of stomach contents during induction of anaesthesia Lancet 1961 2 404-6 The original description

Views and Grades

Mallampati SR Gatt SP et al A clinical sign to predict difficult tracheal intubation a prospective study Can Anaesth Soc J 198532(4)429-434 The original paper describing the classification system but only 3 grades (III and IV combined)

Samsoon GLT and Young JRB Difficult tracheal intubation a retrospective study Anaesthesia 198742487-490 Describes the addition of Mallampati class 4

Cormack RS and Lehane J Difficult tracheal intubation in obstetrics Anaesthesia 1984391105-1111 Describes the laryngoscopy grades and correlates with difficult intubation Also proposes a technique of attempting to intubate while intentionally achieving a suboptimal (Class III) view

Studies of Predictive Indices

There are many studies some which counter others One difficulty is defining a difficult airway Most use a Cormack-Lehane laryngoscopy grade of III-IV Some investigate specific radiographic measurements that are impractical in daily clinical practice Below are a few useful references

El-Ganzouri AR McCarthy RJ et al Preoperative airway assessment Predictive value of a multivariate risk index Anesth Analg 1996821197-1204 A logistic regression comparing examination tests and developing a risk index

Chou HC Wu TL et al Mandibulohyoid distance in difficult laryngoscopy Br J Anaesth 1993 71335-339 A single article sighting this distance as an important factor in an analysis of only 11 patients

Frerk CM Predicting difficult intubation Anaesthesia 1991461005-1008 A study suggesting that a Mallampati Class III or IV with thyromental distance of lt7cm is sensitive and specific for difficult intubation (laryngoscopy grade 3 or 4)

C-Spine Evaluation

mohammad reza rajabi

Page 38 432012

Hoffman JR Mower WR et al Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma N Engl J Med 200034394-99 Application of the NEXUS criteria

mohammad reza rajabi

Page 12 432012

Inability to extend the neck

Yes No

(yes)Correct

The sniffing position requires significant neck extension

(no)Incorrect

The sniffing position requires significant neck extension

Inability to breathe through the nose

Yes No

(no)Correct

Unless a nasal intubation is planned

(yes)Incorrect

Unless a nasal intubation is planned

Large tongue

Yes No

(yes)Correct

Also if it is immobile as from radiation therapy

(no)Incorrect

Also if it is immobile as from radiation therapy

Redundant pharyngeal tissue

Yes No

(yes)Correct

This occurs with obesity and is often suggested by a history of

snoring andor obstructive sleep apnea

mohammad reza rajabi

Page 13 432012

(no)Incorrect

This occurs with obesity and is often suggested by a history of snoring andor obstructive sleep apnea

Case 2 Abnormal Exam

A healthy 25-year-old man is scheduled to have a shoulder repair requiring general anesthesia

Lets review his airway examination

What would you like the patient to do

Open his mouth as wide as possible

Extend his neck as far as possible without pain

View from the side

mohammad reza rajabi

Page 14 432012

Open Mouth

This patients mouth opening is 2 finger-breadths the soft palate is

barely visible on maximal mouth opening

Neck

mohammad reza rajabi

Page 15 432012

View from the side

2 finger-breadths fit between the tip of the chin and the neck

Airway Examination

Mouth opening

Normal

Reduced

What is mouth opening

(normal)Incorrect

it is less than 3 finger breadths

mohammad reza rajabi

Page 16 432012

(reduced)Correct

The mouth opening is less than 3 finger-breadths

Open Mouth

The inter-incisor distance on maximal mouth opening Should be gt4 cm in an adult or 3-4 of the patients finger-breadths

This patients mouth opening is 2 finger breadths the soft palate is barely visible on maximal mouth opening

Mallampati Score

I

II

III

IV

What is Mallampati Score

mohammad reza rajabi

Page 17 432012

(I)Incorrect

The uvula cannot be seen

(II)Incorrect

Not even the top of the uvula is visible

(III)Yes

All structures visible up to the soft palate is a Mallampati Class III

(IV)Incorrect

The soft palate is visible

Mentum-Hyoid distance

Normal

Reduced

What distance

(normal)Incorrect

3 finger-breadths is normal this patient has only 2

(reduced)Yes

this is less than the normal 3 finger-breadths

View from the side

2 finger-breadths fit between the tip of the chin and the neck

mohammad reza rajabi

Page 18 432012

Neck Extension

Normal

Reduced

What is neck extension

(normal)Correct

The neck extends

(reduced)Incorrect

The neck motion is gt 90 degrees

Neck

The range of motion should be more than 90deg Motion less than 80deg may triple the risk

of a poor view at laryngoscopy

Airway Evaluation Summary

Because of the reduced mentum-hyoid distance it may be difficult to visualize the larynx with traditional direct laryngoscopy There are

other options including other blades and techniques that do not require a direct line-of-sight which are beyond the scope of this site

Perhaps the most conservative method of securing the airway of a

patient who is anticipated to have a difficult airway is with awake

fiberoptic intubation This technique requires substantial skill but allows intubation in an awake spontaneously breathing patient The

trachea is identified with a flexible fiberscope and then the endotracheal tube is advanced over the fiberscope like a stylet Such

mohammad reza rajabi

Page 19 432012

a procedure requires blockade of the sensory innervation to the

airway and blunting of the gag reflex

Innervation of the Upper Airway

Awake fiberoptic intubation requires topical anesthesia for patient

comfort as well as to blunt the gag reflex that would prevent successful intubation of the trachea

Several nerves are involved in the sensation of the upper airway

Anterior 23 of the tongue - Trigeminal nerve (V)

Posterior 13 of tongue to epiglottis - Glossopharyngeal nerve (IX afferent limb of gag reflex)

Epiglottis to vocal cords - Internal branch of Superior Laryngeal Nerve (Vagus X)

mohammad reza rajabi

Page 20 432012

Trachea below vocal cords - Recurrent Laryngeal Nerve

(Vagus X)

MOTOR INNERVATION

Motor innervation to the larynx is provided by the Vagus Nerve but recall there are two branches involved The Recurrent Laryngeal

Nerve innervates all the muscles of the larynx EXCEPT the

cricothyroid muscle which is innervated by the External Branch of the Superior Laryngeal Nerve Because the function of the

cricothyroid muscle is to stretch and tense the vocal cords unopposed action of the cricothyroid as may occur with bilateral

destruction of the recurrent laryngeal nerves would lead to stridor respiratory distress and possibly airway obstruction

GAG REFLEX

So the sensory afferent limb of the gag reflex is the glossopharyngeal nerve (IX) while the motor efferent limb is the

Vagus (X)

Its not much of a mnemonic but I remember this as a variant of TGIF Thank God its Recurrent I know its lame perhaps just

lame enough to be memorable

Airway Blocks

Topical application of local anesthetics is usually sufficient for the tongue and oronasopharynx though glossopharyngeal blocks are

performed occasionally Blunting of the gag reflex requires Transtracheal (really translaryngeal) with or without bilateral

Superior Laryngeal Nerve blocks as shown below

mohammad reza rajabi

Page 21 432012

The superior laryngeal nerves are blocked by deposition of 1 lidocaine near where the nerves penetrate the thyrohyoid

membrane The transtracheal block is accomplished with 4 lidocaine injected directly into the tracheal lumen Often this block

alone coupled with nebulized or atomized lidocaine is sufficient for awake intubation

mohammad reza rajabi

Page 22 432012

Airway Structures

The right panel displays images seen during fiberoptic bronchoscopy The corresponding level on CT is displayed on the middle panel

Place the cursor over structures to learn their identity

mohammad reza rajabi

Page 23 432012

mohammad reza rajabi

Page 24 432012

Review of Airway Innervation

Lets review the innervation of the upper airway

mohammad reza rajabi

Page 25 432012

Purple

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(V)Yes

The maxillary branch (V2) supplies the nasal cavity and palate while the mandibular branch (V3) supplies the anterior 23 of the tongue

(IX)Incorrect

The glossopharyngeal nerve supplies sensation to the posterior 13

of the tongue and its overlying structures including the soft palate

(X)No

The vagus innervates the airway further distal

Green

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)Yes

The glossopharyngeal nerve supplies sensation to the posterior 13

of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(X)No

The vagus innervates the airway further distal

mohammad reza rajabi

Page 26 432012

Blue

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)No

The glossopharyngeal nerve supplies sensation to the posterior 13 of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(x)Yes but which branch

Internal branch of superior laryngeal

External branch of superior laryngeal

Recurrent laryngeal

(Yes

The Internal Branch of the Superior Laryngeal Nerve provides

sensory innervation to the mucous membrane from the epiglottis to

and including the vocal cords

Incorrect

The External Branch of the Superior Laryngeal nerve provides motor innervation to the cricothyroid muscle only

Incorrect

The Recurrent Laryngeal Nerve supplies sensory innervation to the

trachea below the vocal cords as well as motor innervation to all the

intrinsic muscles of the larynx except the cricothyroid muscle)

mohammad reza rajabi

Page 27 432012

Red

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)No

The glossopharyngeal nerve supplies sensation to the posterior 13 of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(x)Yes but which branch

Internal branch of superior laryngeal

External branch of superior laryngeal

Recurrent laryngeal

(Incorrect

The Internal Branch of the Superior Laryngeal Nerve provides sensory innervation to the mucous membrane from the epiglottis to

and including the vocal cords

Incorrect

The External Branch of the Superior Laryngeal nerve provides motor innervation to the cricothyroid muscle only

Yes

The Recurrent Laryngeal Nerve supplies sensory innervation to the

trachea below the vocal cords as well as motor innervation to all the

intrinsic muscles of the larynx except the cricothyroid muscle)

mohammad reza rajabi

Page 28 432012

Case 3 Spine Evaluation

A previously healthy 40-year-old male presents with an open femur fracture from a Motor Vehicle Accident (MVA) that needs to be

repaired under general anesthesia He is currently on a backboard

with a cervical collar in place and is hemodynamically stable

Examination of this patients airway is complicated by the presence of the cervical collar which both inhibits mouth opening and by

definition prevents neck extension As you have seen above neck extension is required for direct laryngoscopy

So what shall we do

Remove the neck collar and intubate as usual

Intubate with a technique that does not require neck movement

Avoid general anesthesia and perform a regional block for the

procedure

Perform studies to clear the cervical spine

First a basic review of the anatomy is helpful

Recall that the cervical spine consists of 7 vertebrae the first two of

which are highly specialized

(Should this patient have an unstable cervical spine the movement resulting from laryngoscopy could permanently damage the spinal

cord likely resulting in quadriplegia)

(There are numerous techniques (retrograde intubationhellip) purported

to involve less cervical spine motion each of which requires substantial skill and experience These should only be attempted by

experienced practitioners Some advocate in-line stabilization where a second person attempts to hold the cervical spine still while

the primary person attempts direct laryngoscopy This technique makes intubation more difficult and is inadequate for stabilization)

mohammad reza rajabi

Page 29 432012

(While an attractive option many would argue that anytime a

regional anesthetic is planned immediate endotracheal intubation must be possible Complications may occur during the regional block

or it may be inadequate for the operation or wear off before the surgeons are done Therefore inability to emergently intubate a

patient is a relative contraindication to regional anesthesia and should be considered in this patient with a possible unstable neck)

(Great idea)

Cervical Spine Anatomy-Atlas

C1 The Atlas is a ring that interacts with the skull base above and

C2 shown on next page It is unique in that it lacks a vertebral body and spinous process The articulation of C1 with the occiput is very

tight providing little of the flexion of the cervical spine and only about 20 degrees of extension

mohammad reza rajabi

Page 30 432012

Cervical Spine Anatomy-Axis

C2 The Axis has an unusual thumb-like extension of its vertebral body that passes through the arch of C1 This process is called the

dens or odontoid The odontoid process is normally held very tightly against the anterior arch of C1 by the transverse ligament

Meanwhile the spinal cord travels behind the odontoid within the

arch of C1

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Page 31 432012

Atlanto Axial Joint

This atlanto-axial joint provides the majority of the rotational motion of the cervical spine Meanwhile flexion and extension are primarily

accomplished at C2 and below and particularly between C4 and C6

Neck Movement with DL

What happens to the neck during direct laryngoscopy and

intubation

As you have seen the sniffing position involves neck flexion in the lower cervical spine with extension superiorly In the process of

direct laryngoscopy this motion is accentuated As the laryngoscope

is lifted upward the occiput is extended primarily at the atlanto-occipital joint (occiput-C1) while flexion occurs at C2-3 and below

Therefore any intervention that impedes this flexion and extension

will make visualization of the glottis more difficult In someone with a cervical fusion up to the occiput it is pretty much impossible to

perform direct laryngoscopy Similarly a patient with external stabilization such as a c-collar in this case will (SHOULD) have neck

movement reduced sufficient to make visualization difficult if not impossible

mohammad reza rajabi

Page 32 432012

Clearing the C-Spine

How does one rule out damage to the cervical spine

At present history is our greatest ally If the healthy patient has no history of neck problems and no symptoms on maximal flexion and

extension they are unlikely to have cervical spine disease

On the other hand there are many patients whose cervical spine

SHOULD be radiographically evaluated pre-operatively including certain trauma patients as well as those with disease states that

affect the cervical spine including rheumatoid arthritis and Downs Syndrome These diseases may affect the transverse ligament and

thus the stability at the atlanto-axial joint

Nexus Criteria

Which trauma patients require cervical spine films prior to surgery or

intubation There is a set of criteria identified by the National Emergency X-

Radiography Utilization Study (NEXUS) that attempt to identify patients with a low probability of injury thereby reducing the

number of negative cervical spine radiographs taken

The criteria include No midline cervical tenderness

No focal neurologic deficit

Normal alertness

No intoxication

No painful distracting injury that might make them ignore their

neck pain

For those patients whose cervical spine is not cleared the

anesthesiologist must consider the risks of cervical spine damage that can be worsened through direct laryngoscopy versus the risk of

alternative techniques that may minimize neck motion including awake fiberoptic intubation A description of these alternate

techniques is beyond the scope of this site at present

mohammad reza rajabi

Page 33 432012

Spine Film

For the current case the following film is obtained

Patients Film

Normal for Comparison

mohammad reza rajabi

Page 34 432012

Explanation

Note the large step-off between C6 and C7 This subluxation causes entrapment of the spinal cord and damage

Therefore this patient requires an intubation technique with minimal neck motion and awake positioningas well as some external

stabilization or operative intervention to prevent damage to the spinal cord at the neck

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Page 35 432012

C-Spine Review

So which patients are at higher risk for neck injury during intubation

Trauma patients

Yes No

(yes)Correct

They may have trauma to the cervical spine as well

(no)Incorrect

They may have trauma to the cervical spine as well

Rheumatoid arthritis patients

Yes No

(yes)Correct

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

(no)Incorrect

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

Downs Syndrome patients

Yes No

(yes)Correct

About 15 of these patients have laxity in the transverse ligament

that holds the odontoid against the anterior arch of C1 Xrays are also recommended in these patients prior to anticipated neck

manipulation including laryngoscopy

mohammad reza rajabi

Page 36 432012

(no)Incorrect

About 15 of these patients have laxity in the transverse ligament that holds the odontoid against the anterior arch of C1 Xrays are

also recommended in these patients prior to anticipated neck manipulation including laryngoscopy

Osteoarthritic patients

Yes No

(yes)Incorrect

They are not at higher risk

(no)Correct

They are not at higher risk

Patient with a prior cervical spine fusion

Yes No

(yes)Incorrect

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

(no)Correct

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

mohammad reza rajabi

Page 37 432012

Airway References

Cricoid Pressure

Vanner RG Asai T Safe use of cricoid pressure Anaesthesia 1999 54 1-3 A review of literature with recommendations

Sellick BA Cricoid pressure to control regurgitation of stomach contents during induction of anaesthesia Lancet 1961 2 404-6 The original description

Views and Grades

Mallampati SR Gatt SP et al A clinical sign to predict difficult tracheal intubation a prospective study Can Anaesth Soc J 198532(4)429-434 The original paper describing the classification system but only 3 grades (III and IV combined)

Samsoon GLT and Young JRB Difficult tracheal intubation a retrospective study Anaesthesia 198742487-490 Describes the addition of Mallampati class 4

Cormack RS and Lehane J Difficult tracheal intubation in obstetrics Anaesthesia 1984391105-1111 Describes the laryngoscopy grades and correlates with difficult intubation Also proposes a technique of attempting to intubate while intentionally achieving a suboptimal (Class III) view

Studies of Predictive Indices

There are many studies some which counter others One difficulty is defining a difficult airway Most use a Cormack-Lehane laryngoscopy grade of III-IV Some investigate specific radiographic measurements that are impractical in daily clinical practice Below are a few useful references

El-Ganzouri AR McCarthy RJ et al Preoperative airway assessment Predictive value of a multivariate risk index Anesth Analg 1996821197-1204 A logistic regression comparing examination tests and developing a risk index

Chou HC Wu TL et al Mandibulohyoid distance in difficult laryngoscopy Br J Anaesth 1993 71335-339 A single article sighting this distance as an important factor in an analysis of only 11 patients

Frerk CM Predicting difficult intubation Anaesthesia 1991461005-1008 A study suggesting that a Mallampati Class III or IV with thyromental distance of lt7cm is sensitive and specific for difficult intubation (laryngoscopy grade 3 or 4)

C-Spine Evaluation

mohammad reza rajabi

Page 38 432012

Hoffman JR Mower WR et al Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma N Engl J Med 200034394-99 Application of the NEXUS criteria

mohammad reza rajabi

Page 13 432012

(no)Incorrect

This occurs with obesity and is often suggested by a history of snoring andor obstructive sleep apnea

Case 2 Abnormal Exam

A healthy 25-year-old man is scheduled to have a shoulder repair requiring general anesthesia

Lets review his airway examination

What would you like the patient to do

Open his mouth as wide as possible

Extend his neck as far as possible without pain

View from the side

mohammad reza rajabi

Page 14 432012

Open Mouth

This patients mouth opening is 2 finger-breadths the soft palate is

barely visible on maximal mouth opening

Neck

mohammad reza rajabi

Page 15 432012

View from the side

2 finger-breadths fit between the tip of the chin and the neck

Airway Examination

Mouth opening

Normal

Reduced

What is mouth opening

(normal)Incorrect

it is less than 3 finger breadths

mohammad reza rajabi

Page 16 432012

(reduced)Correct

The mouth opening is less than 3 finger-breadths

Open Mouth

The inter-incisor distance on maximal mouth opening Should be gt4 cm in an adult or 3-4 of the patients finger-breadths

This patients mouth opening is 2 finger breadths the soft palate is barely visible on maximal mouth opening

Mallampati Score

I

II

III

IV

What is Mallampati Score

mohammad reza rajabi

Page 17 432012

(I)Incorrect

The uvula cannot be seen

(II)Incorrect

Not even the top of the uvula is visible

(III)Yes

All structures visible up to the soft palate is a Mallampati Class III

(IV)Incorrect

The soft palate is visible

Mentum-Hyoid distance

Normal

Reduced

What distance

(normal)Incorrect

3 finger-breadths is normal this patient has only 2

(reduced)Yes

this is less than the normal 3 finger-breadths

View from the side

2 finger-breadths fit between the tip of the chin and the neck

mohammad reza rajabi

Page 18 432012

Neck Extension

Normal

Reduced

What is neck extension

(normal)Correct

The neck extends

(reduced)Incorrect

The neck motion is gt 90 degrees

Neck

The range of motion should be more than 90deg Motion less than 80deg may triple the risk

of a poor view at laryngoscopy

Airway Evaluation Summary

Because of the reduced mentum-hyoid distance it may be difficult to visualize the larynx with traditional direct laryngoscopy There are

other options including other blades and techniques that do not require a direct line-of-sight which are beyond the scope of this site

Perhaps the most conservative method of securing the airway of a

patient who is anticipated to have a difficult airway is with awake

fiberoptic intubation This technique requires substantial skill but allows intubation in an awake spontaneously breathing patient The

trachea is identified with a flexible fiberscope and then the endotracheal tube is advanced over the fiberscope like a stylet Such

mohammad reza rajabi

Page 19 432012

a procedure requires blockade of the sensory innervation to the

airway and blunting of the gag reflex

Innervation of the Upper Airway

Awake fiberoptic intubation requires topical anesthesia for patient

comfort as well as to blunt the gag reflex that would prevent successful intubation of the trachea

Several nerves are involved in the sensation of the upper airway

Anterior 23 of the tongue - Trigeminal nerve (V)

Posterior 13 of tongue to epiglottis - Glossopharyngeal nerve (IX afferent limb of gag reflex)

Epiglottis to vocal cords - Internal branch of Superior Laryngeal Nerve (Vagus X)

mohammad reza rajabi

Page 20 432012

Trachea below vocal cords - Recurrent Laryngeal Nerve

(Vagus X)

MOTOR INNERVATION

Motor innervation to the larynx is provided by the Vagus Nerve but recall there are two branches involved The Recurrent Laryngeal

Nerve innervates all the muscles of the larynx EXCEPT the

cricothyroid muscle which is innervated by the External Branch of the Superior Laryngeal Nerve Because the function of the

cricothyroid muscle is to stretch and tense the vocal cords unopposed action of the cricothyroid as may occur with bilateral

destruction of the recurrent laryngeal nerves would lead to stridor respiratory distress and possibly airway obstruction

GAG REFLEX

So the sensory afferent limb of the gag reflex is the glossopharyngeal nerve (IX) while the motor efferent limb is the

Vagus (X)

Its not much of a mnemonic but I remember this as a variant of TGIF Thank God its Recurrent I know its lame perhaps just

lame enough to be memorable

Airway Blocks

Topical application of local anesthetics is usually sufficient for the tongue and oronasopharynx though glossopharyngeal blocks are

performed occasionally Blunting of the gag reflex requires Transtracheal (really translaryngeal) with or without bilateral

Superior Laryngeal Nerve blocks as shown below

mohammad reza rajabi

Page 21 432012

The superior laryngeal nerves are blocked by deposition of 1 lidocaine near where the nerves penetrate the thyrohyoid

membrane The transtracheal block is accomplished with 4 lidocaine injected directly into the tracheal lumen Often this block

alone coupled with nebulized or atomized lidocaine is sufficient for awake intubation

mohammad reza rajabi

Page 22 432012

Airway Structures

The right panel displays images seen during fiberoptic bronchoscopy The corresponding level on CT is displayed on the middle panel

Place the cursor over structures to learn their identity

mohammad reza rajabi

Page 23 432012

mohammad reza rajabi

Page 24 432012

Review of Airway Innervation

Lets review the innervation of the upper airway

mohammad reza rajabi

Page 25 432012

Purple

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(V)Yes

The maxillary branch (V2) supplies the nasal cavity and palate while the mandibular branch (V3) supplies the anterior 23 of the tongue

(IX)Incorrect

The glossopharyngeal nerve supplies sensation to the posterior 13

of the tongue and its overlying structures including the soft palate

(X)No

The vagus innervates the airway further distal

Green

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)Yes

The glossopharyngeal nerve supplies sensation to the posterior 13

of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(X)No

The vagus innervates the airway further distal

mohammad reza rajabi

Page 26 432012

Blue

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)No

The glossopharyngeal nerve supplies sensation to the posterior 13 of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(x)Yes but which branch

Internal branch of superior laryngeal

External branch of superior laryngeal

Recurrent laryngeal

(Yes

The Internal Branch of the Superior Laryngeal Nerve provides

sensory innervation to the mucous membrane from the epiglottis to

and including the vocal cords

Incorrect

The External Branch of the Superior Laryngeal nerve provides motor innervation to the cricothyroid muscle only

Incorrect

The Recurrent Laryngeal Nerve supplies sensory innervation to the

trachea below the vocal cords as well as motor innervation to all the

intrinsic muscles of the larynx except the cricothyroid muscle)

mohammad reza rajabi

Page 27 432012

Red

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)No

The glossopharyngeal nerve supplies sensation to the posterior 13 of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(x)Yes but which branch

Internal branch of superior laryngeal

External branch of superior laryngeal

Recurrent laryngeal

(Incorrect

The Internal Branch of the Superior Laryngeal Nerve provides sensory innervation to the mucous membrane from the epiglottis to

and including the vocal cords

Incorrect

The External Branch of the Superior Laryngeal nerve provides motor innervation to the cricothyroid muscle only

Yes

The Recurrent Laryngeal Nerve supplies sensory innervation to the

trachea below the vocal cords as well as motor innervation to all the

intrinsic muscles of the larynx except the cricothyroid muscle)

mohammad reza rajabi

Page 28 432012

Case 3 Spine Evaluation

A previously healthy 40-year-old male presents with an open femur fracture from a Motor Vehicle Accident (MVA) that needs to be

repaired under general anesthesia He is currently on a backboard

with a cervical collar in place and is hemodynamically stable

Examination of this patients airway is complicated by the presence of the cervical collar which both inhibits mouth opening and by

definition prevents neck extension As you have seen above neck extension is required for direct laryngoscopy

So what shall we do

Remove the neck collar and intubate as usual

Intubate with a technique that does not require neck movement

Avoid general anesthesia and perform a regional block for the

procedure

Perform studies to clear the cervical spine

First a basic review of the anatomy is helpful

Recall that the cervical spine consists of 7 vertebrae the first two of

which are highly specialized

(Should this patient have an unstable cervical spine the movement resulting from laryngoscopy could permanently damage the spinal

cord likely resulting in quadriplegia)

(There are numerous techniques (retrograde intubationhellip) purported

to involve less cervical spine motion each of which requires substantial skill and experience These should only be attempted by

experienced practitioners Some advocate in-line stabilization where a second person attempts to hold the cervical spine still while

the primary person attempts direct laryngoscopy This technique makes intubation more difficult and is inadequate for stabilization)

mohammad reza rajabi

Page 29 432012

(While an attractive option many would argue that anytime a

regional anesthetic is planned immediate endotracheal intubation must be possible Complications may occur during the regional block

or it may be inadequate for the operation or wear off before the surgeons are done Therefore inability to emergently intubate a

patient is a relative contraindication to regional anesthesia and should be considered in this patient with a possible unstable neck)

(Great idea)

Cervical Spine Anatomy-Atlas

C1 The Atlas is a ring that interacts with the skull base above and

C2 shown on next page It is unique in that it lacks a vertebral body and spinous process The articulation of C1 with the occiput is very

tight providing little of the flexion of the cervical spine and only about 20 degrees of extension

mohammad reza rajabi

Page 30 432012

Cervical Spine Anatomy-Axis

C2 The Axis has an unusual thumb-like extension of its vertebral body that passes through the arch of C1 This process is called the

dens or odontoid The odontoid process is normally held very tightly against the anterior arch of C1 by the transverse ligament

Meanwhile the spinal cord travels behind the odontoid within the

arch of C1

mohammad reza rajabi

Page 31 432012

Atlanto Axial Joint

This atlanto-axial joint provides the majority of the rotational motion of the cervical spine Meanwhile flexion and extension are primarily

accomplished at C2 and below and particularly between C4 and C6

Neck Movement with DL

What happens to the neck during direct laryngoscopy and

intubation

As you have seen the sniffing position involves neck flexion in the lower cervical spine with extension superiorly In the process of

direct laryngoscopy this motion is accentuated As the laryngoscope

is lifted upward the occiput is extended primarily at the atlanto-occipital joint (occiput-C1) while flexion occurs at C2-3 and below

Therefore any intervention that impedes this flexion and extension

will make visualization of the glottis more difficult In someone with a cervical fusion up to the occiput it is pretty much impossible to

perform direct laryngoscopy Similarly a patient with external stabilization such as a c-collar in this case will (SHOULD) have neck

movement reduced sufficient to make visualization difficult if not impossible

mohammad reza rajabi

Page 32 432012

Clearing the C-Spine

How does one rule out damage to the cervical spine

At present history is our greatest ally If the healthy patient has no history of neck problems and no symptoms on maximal flexion and

extension they are unlikely to have cervical spine disease

On the other hand there are many patients whose cervical spine

SHOULD be radiographically evaluated pre-operatively including certain trauma patients as well as those with disease states that

affect the cervical spine including rheumatoid arthritis and Downs Syndrome These diseases may affect the transverse ligament and

thus the stability at the atlanto-axial joint

Nexus Criteria

Which trauma patients require cervical spine films prior to surgery or

intubation There is a set of criteria identified by the National Emergency X-

Radiography Utilization Study (NEXUS) that attempt to identify patients with a low probability of injury thereby reducing the

number of negative cervical spine radiographs taken

The criteria include No midline cervical tenderness

No focal neurologic deficit

Normal alertness

No intoxication

No painful distracting injury that might make them ignore their

neck pain

For those patients whose cervical spine is not cleared the

anesthesiologist must consider the risks of cervical spine damage that can be worsened through direct laryngoscopy versus the risk of

alternative techniques that may minimize neck motion including awake fiberoptic intubation A description of these alternate

techniques is beyond the scope of this site at present

mohammad reza rajabi

Page 33 432012

Spine Film

For the current case the following film is obtained

Patients Film

Normal for Comparison

mohammad reza rajabi

Page 34 432012

Explanation

Note the large step-off between C6 and C7 This subluxation causes entrapment of the spinal cord and damage

Therefore this patient requires an intubation technique with minimal neck motion and awake positioningas well as some external

stabilization or operative intervention to prevent damage to the spinal cord at the neck

mohammad reza rajabi

Page 35 432012

C-Spine Review

So which patients are at higher risk for neck injury during intubation

Trauma patients

Yes No

(yes)Correct

They may have trauma to the cervical spine as well

(no)Incorrect

They may have trauma to the cervical spine as well

Rheumatoid arthritis patients

Yes No

(yes)Correct

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

(no)Incorrect

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

Downs Syndrome patients

Yes No

(yes)Correct

About 15 of these patients have laxity in the transverse ligament

that holds the odontoid against the anterior arch of C1 Xrays are also recommended in these patients prior to anticipated neck

manipulation including laryngoscopy

mohammad reza rajabi

Page 36 432012

(no)Incorrect

About 15 of these patients have laxity in the transverse ligament that holds the odontoid against the anterior arch of C1 Xrays are

also recommended in these patients prior to anticipated neck manipulation including laryngoscopy

Osteoarthritic patients

Yes No

(yes)Incorrect

They are not at higher risk

(no)Correct

They are not at higher risk

Patient with a prior cervical spine fusion

Yes No

(yes)Incorrect

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

(no)Correct

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

mohammad reza rajabi

Page 37 432012

Airway References

Cricoid Pressure

Vanner RG Asai T Safe use of cricoid pressure Anaesthesia 1999 54 1-3 A review of literature with recommendations

Sellick BA Cricoid pressure to control regurgitation of stomach contents during induction of anaesthesia Lancet 1961 2 404-6 The original description

Views and Grades

Mallampati SR Gatt SP et al A clinical sign to predict difficult tracheal intubation a prospective study Can Anaesth Soc J 198532(4)429-434 The original paper describing the classification system but only 3 grades (III and IV combined)

Samsoon GLT and Young JRB Difficult tracheal intubation a retrospective study Anaesthesia 198742487-490 Describes the addition of Mallampati class 4

Cormack RS and Lehane J Difficult tracheal intubation in obstetrics Anaesthesia 1984391105-1111 Describes the laryngoscopy grades and correlates with difficult intubation Also proposes a technique of attempting to intubate while intentionally achieving a suboptimal (Class III) view

Studies of Predictive Indices

There are many studies some which counter others One difficulty is defining a difficult airway Most use a Cormack-Lehane laryngoscopy grade of III-IV Some investigate specific radiographic measurements that are impractical in daily clinical practice Below are a few useful references

El-Ganzouri AR McCarthy RJ et al Preoperative airway assessment Predictive value of a multivariate risk index Anesth Analg 1996821197-1204 A logistic regression comparing examination tests and developing a risk index

Chou HC Wu TL et al Mandibulohyoid distance in difficult laryngoscopy Br J Anaesth 1993 71335-339 A single article sighting this distance as an important factor in an analysis of only 11 patients

Frerk CM Predicting difficult intubation Anaesthesia 1991461005-1008 A study suggesting that a Mallampati Class III or IV with thyromental distance of lt7cm is sensitive and specific for difficult intubation (laryngoscopy grade 3 or 4)

C-Spine Evaluation

mohammad reza rajabi

Page 38 432012

Hoffman JR Mower WR et al Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma N Engl J Med 200034394-99 Application of the NEXUS criteria

mohammad reza rajabi

Page 14 432012

Open Mouth

This patients mouth opening is 2 finger-breadths the soft palate is

barely visible on maximal mouth opening

Neck

mohammad reza rajabi

Page 15 432012

View from the side

2 finger-breadths fit between the tip of the chin and the neck

Airway Examination

Mouth opening

Normal

Reduced

What is mouth opening

(normal)Incorrect

it is less than 3 finger breadths

mohammad reza rajabi

Page 16 432012

(reduced)Correct

The mouth opening is less than 3 finger-breadths

Open Mouth

The inter-incisor distance on maximal mouth opening Should be gt4 cm in an adult or 3-4 of the patients finger-breadths

This patients mouth opening is 2 finger breadths the soft palate is barely visible on maximal mouth opening

Mallampati Score

I

II

III

IV

What is Mallampati Score

mohammad reza rajabi

Page 17 432012

(I)Incorrect

The uvula cannot be seen

(II)Incorrect

Not even the top of the uvula is visible

(III)Yes

All structures visible up to the soft palate is a Mallampati Class III

(IV)Incorrect

The soft palate is visible

Mentum-Hyoid distance

Normal

Reduced

What distance

(normal)Incorrect

3 finger-breadths is normal this patient has only 2

(reduced)Yes

this is less than the normal 3 finger-breadths

View from the side

2 finger-breadths fit between the tip of the chin and the neck

mohammad reza rajabi

Page 18 432012

Neck Extension

Normal

Reduced

What is neck extension

(normal)Correct

The neck extends

(reduced)Incorrect

The neck motion is gt 90 degrees

Neck

The range of motion should be more than 90deg Motion less than 80deg may triple the risk

of a poor view at laryngoscopy

Airway Evaluation Summary

Because of the reduced mentum-hyoid distance it may be difficult to visualize the larynx with traditional direct laryngoscopy There are

other options including other blades and techniques that do not require a direct line-of-sight which are beyond the scope of this site

Perhaps the most conservative method of securing the airway of a

patient who is anticipated to have a difficult airway is with awake

fiberoptic intubation This technique requires substantial skill but allows intubation in an awake spontaneously breathing patient The

trachea is identified with a flexible fiberscope and then the endotracheal tube is advanced over the fiberscope like a stylet Such

mohammad reza rajabi

Page 19 432012

a procedure requires blockade of the sensory innervation to the

airway and blunting of the gag reflex

Innervation of the Upper Airway

Awake fiberoptic intubation requires topical anesthesia for patient

comfort as well as to blunt the gag reflex that would prevent successful intubation of the trachea

Several nerves are involved in the sensation of the upper airway

Anterior 23 of the tongue - Trigeminal nerve (V)

Posterior 13 of tongue to epiglottis - Glossopharyngeal nerve (IX afferent limb of gag reflex)

Epiglottis to vocal cords - Internal branch of Superior Laryngeal Nerve (Vagus X)

mohammad reza rajabi

Page 20 432012

Trachea below vocal cords - Recurrent Laryngeal Nerve

(Vagus X)

MOTOR INNERVATION

Motor innervation to the larynx is provided by the Vagus Nerve but recall there are two branches involved The Recurrent Laryngeal

Nerve innervates all the muscles of the larynx EXCEPT the

cricothyroid muscle which is innervated by the External Branch of the Superior Laryngeal Nerve Because the function of the

cricothyroid muscle is to stretch and tense the vocal cords unopposed action of the cricothyroid as may occur with bilateral

destruction of the recurrent laryngeal nerves would lead to stridor respiratory distress and possibly airway obstruction

GAG REFLEX

So the sensory afferent limb of the gag reflex is the glossopharyngeal nerve (IX) while the motor efferent limb is the

Vagus (X)

Its not much of a mnemonic but I remember this as a variant of TGIF Thank God its Recurrent I know its lame perhaps just

lame enough to be memorable

Airway Blocks

Topical application of local anesthetics is usually sufficient for the tongue and oronasopharynx though glossopharyngeal blocks are

performed occasionally Blunting of the gag reflex requires Transtracheal (really translaryngeal) with or without bilateral

Superior Laryngeal Nerve blocks as shown below

mohammad reza rajabi

Page 21 432012

The superior laryngeal nerves are blocked by deposition of 1 lidocaine near where the nerves penetrate the thyrohyoid

membrane The transtracheal block is accomplished with 4 lidocaine injected directly into the tracheal lumen Often this block

alone coupled with nebulized or atomized lidocaine is sufficient for awake intubation

mohammad reza rajabi

Page 22 432012

Airway Structures

The right panel displays images seen during fiberoptic bronchoscopy The corresponding level on CT is displayed on the middle panel

Place the cursor over structures to learn their identity

mohammad reza rajabi

Page 23 432012

mohammad reza rajabi

Page 24 432012

Review of Airway Innervation

Lets review the innervation of the upper airway

mohammad reza rajabi

Page 25 432012

Purple

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(V)Yes

The maxillary branch (V2) supplies the nasal cavity and palate while the mandibular branch (V3) supplies the anterior 23 of the tongue

(IX)Incorrect

The glossopharyngeal nerve supplies sensation to the posterior 13

of the tongue and its overlying structures including the soft palate

(X)No

The vagus innervates the airway further distal

Green

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)Yes

The glossopharyngeal nerve supplies sensation to the posterior 13

of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(X)No

The vagus innervates the airway further distal

mohammad reza rajabi

Page 26 432012

Blue

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)No

The glossopharyngeal nerve supplies sensation to the posterior 13 of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(x)Yes but which branch

Internal branch of superior laryngeal

External branch of superior laryngeal

Recurrent laryngeal

(Yes

The Internal Branch of the Superior Laryngeal Nerve provides

sensory innervation to the mucous membrane from the epiglottis to

and including the vocal cords

Incorrect

The External Branch of the Superior Laryngeal nerve provides motor innervation to the cricothyroid muscle only

Incorrect

The Recurrent Laryngeal Nerve supplies sensory innervation to the

trachea below the vocal cords as well as motor innervation to all the

intrinsic muscles of the larynx except the cricothyroid muscle)

mohammad reza rajabi

Page 27 432012

Red

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)No

The glossopharyngeal nerve supplies sensation to the posterior 13 of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(x)Yes but which branch

Internal branch of superior laryngeal

External branch of superior laryngeal

Recurrent laryngeal

(Incorrect

The Internal Branch of the Superior Laryngeal Nerve provides sensory innervation to the mucous membrane from the epiglottis to

and including the vocal cords

Incorrect

The External Branch of the Superior Laryngeal nerve provides motor innervation to the cricothyroid muscle only

Yes

The Recurrent Laryngeal Nerve supplies sensory innervation to the

trachea below the vocal cords as well as motor innervation to all the

intrinsic muscles of the larynx except the cricothyroid muscle)

mohammad reza rajabi

Page 28 432012

Case 3 Spine Evaluation

A previously healthy 40-year-old male presents with an open femur fracture from a Motor Vehicle Accident (MVA) that needs to be

repaired under general anesthesia He is currently on a backboard

with a cervical collar in place and is hemodynamically stable

Examination of this patients airway is complicated by the presence of the cervical collar which both inhibits mouth opening and by

definition prevents neck extension As you have seen above neck extension is required for direct laryngoscopy

So what shall we do

Remove the neck collar and intubate as usual

Intubate with a technique that does not require neck movement

Avoid general anesthesia and perform a regional block for the

procedure

Perform studies to clear the cervical spine

First a basic review of the anatomy is helpful

Recall that the cervical spine consists of 7 vertebrae the first two of

which are highly specialized

(Should this patient have an unstable cervical spine the movement resulting from laryngoscopy could permanently damage the spinal

cord likely resulting in quadriplegia)

(There are numerous techniques (retrograde intubationhellip) purported

to involve less cervical spine motion each of which requires substantial skill and experience These should only be attempted by

experienced practitioners Some advocate in-line stabilization where a second person attempts to hold the cervical spine still while

the primary person attempts direct laryngoscopy This technique makes intubation more difficult and is inadequate for stabilization)

mohammad reza rajabi

Page 29 432012

(While an attractive option many would argue that anytime a

regional anesthetic is planned immediate endotracheal intubation must be possible Complications may occur during the regional block

or it may be inadequate for the operation or wear off before the surgeons are done Therefore inability to emergently intubate a

patient is a relative contraindication to regional anesthesia and should be considered in this patient with a possible unstable neck)

(Great idea)

Cervical Spine Anatomy-Atlas

C1 The Atlas is a ring that interacts with the skull base above and

C2 shown on next page It is unique in that it lacks a vertebral body and spinous process The articulation of C1 with the occiput is very

tight providing little of the flexion of the cervical spine and only about 20 degrees of extension

mohammad reza rajabi

Page 30 432012

Cervical Spine Anatomy-Axis

C2 The Axis has an unusual thumb-like extension of its vertebral body that passes through the arch of C1 This process is called the

dens or odontoid The odontoid process is normally held very tightly against the anterior arch of C1 by the transverse ligament

Meanwhile the spinal cord travels behind the odontoid within the

arch of C1

mohammad reza rajabi

Page 31 432012

Atlanto Axial Joint

This atlanto-axial joint provides the majority of the rotational motion of the cervical spine Meanwhile flexion and extension are primarily

accomplished at C2 and below and particularly between C4 and C6

Neck Movement with DL

What happens to the neck during direct laryngoscopy and

intubation

As you have seen the sniffing position involves neck flexion in the lower cervical spine with extension superiorly In the process of

direct laryngoscopy this motion is accentuated As the laryngoscope

is lifted upward the occiput is extended primarily at the atlanto-occipital joint (occiput-C1) while flexion occurs at C2-3 and below

Therefore any intervention that impedes this flexion and extension

will make visualization of the glottis more difficult In someone with a cervical fusion up to the occiput it is pretty much impossible to

perform direct laryngoscopy Similarly a patient with external stabilization such as a c-collar in this case will (SHOULD) have neck

movement reduced sufficient to make visualization difficult if not impossible

mohammad reza rajabi

Page 32 432012

Clearing the C-Spine

How does one rule out damage to the cervical spine

At present history is our greatest ally If the healthy patient has no history of neck problems and no symptoms on maximal flexion and

extension they are unlikely to have cervical spine disease

On the other hand there are many patients whose cervical spine

SHOULD be radiographically evaluated pre-operatively including certain trauma patients as well as those with disease states that

affect the cervical spine including rheumatoid arthritis and Downs Syndrome These diseases may affect the transverse ligament and

thus the stability at the atlanto-axial joint

Nexus Criteria

Which trauma patients require cervical spine films prior to surgery or

intubation There is a set of criteria identified by the National Emergency X-

Radiography Utilization Study (NEXUS) that attempt to identify patients with a low probability of injury thereby reducing the

number of negative cervical spine radiographs taken

The criteria include No midline cervical tenderness

No focal neurologic deficit

Normal alertness

No intoxication

No painful distracting injury that might make them ignore their

neck pain

For those patients whose cervical spine is not cleared the

anesthesiologist must consider the risks of cervical spine damage that can be worsened through direct laryngoscopy versus the risk of

alternative techniques that may minimize neck motion including awake fiberoptic intubation A description of these alternate

techniques is beyond the scope of this site at present

mohammad reza rajabi

Page 33 432012

Spine Film

For the current case the following film is obtained

Patients Film

Normal for Comparison

mohammad reza rajabi

Page 34 432012

Explanation

Note the large step-off between C6 and C7 This subluxation causes entrapment of the spinal cord and damage

Therefore this patient requires an intubation technique with minimal neck motion and awake positioningas well as some external

stabilization or operative intervention to prevent damage to the spinal cord at the neck

mohammad reza rajabi

Page 35 432012

C-Spine Review

So which patients are at higher risk for neck injury during intubation

Trauma patients

Yes No

(yes)Correct

They may have trauma to the cervical spine as well

(no)Incorrect

They may have trauma to the cervical spine as well

Rheumatoid arthritis patients

Yes No

(yes)Correct

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

(no)Incorrect

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

Downs Syndrome patients

Yes No

(yes)Correct

About 15 of these patients have laxity in the transverse ligament

that holds the odontoid against the anterior arch of C1 Xrays are also recommended in these patients prior to anticipated neck

manipulation including laryngoscopy

mohammad reza rajabi

Page 36 432012

(no)Incorrect

About 15 of these patients have laxity in the transverse ligament that holds the odontoid against the anterior arch of C1 Xrays are

also recommended in these patients prior to anticipated neck manipulation including laryngoscopy

Osteoarthritic patients

Yes No

(yes)Incorrect

They are not at higher risk

(no)Correct

They are not at higher risk

Patient with a prior cervical spine fusion

Yes No

(yes)Incorrect

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

(no)Correct

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

mohammad reza rajabi

Page 37 432012

Airway References

Cricoid Pressure

Vanner RG Asai T Safe use of cricoid pressure Anaesthesia 1999 54 1-3 A review of literature with recommendations

Sellick BA Cricoid pressure to control regurgitation of stomach contents during induction of anaesthesia Lancet 1961 2 404-6 The original description

Views and Grades

Mallampati SR Gatt SP et al A clinical sign to predict difficult tracheal intubation a prospective study Can Anaesth Soc J 198532(4)429-434 The original paper describing the classification system but only 3 grades (III and IV combined)

Samsoon GLT and Young JRB Difficult tracheal intubation a retrospective study Anaesthesia 198742487-490 Describes the addition of Mallampati class 4

Cormack RS and Lehane J Difficult tracheal intubation in obstetrics Anaesthesia 1984391105-1111 Describes the laryngoscopy grades and correlates with difficult intubation Also proposes a technique of attempting to intubate while intentionally achieving a suboptimal (Class III) view

Studies of Predictive Indices

There are many studies some which counter others One difficulty is defining a difficult airway Most use a Cormack-Lehane laryngoscopy grade of III-IV Some investigate specific radiographic measurements that are impractical in daily clinical practice Below are a few useful references

El-Ganzouri AR McCarthy RJ et al Preoperative airway assessment Predictive value of a multivariate risk index Anesth Analg 1996821197-1204 A logistic regression comparing examination tests and developing a risk index

Chou HC Wu TL et al Mandibulohyoid distance in difficult laryngoscopy Br J Anaesth 1993 71335-339 A single article sighting this distance as an important factor in an analysis of only 11 patients

Frerk CM Predicting difficult intubation Anaesthesia 1991461005-1008 A study suggesting that a Mallampati Class III or IV with thyromental distance of lt7cm is sensitive and specific for difficult intubation (laryngoscopy grade 3 or 4)

C-Spine Evaluation

mohammad reza rajabi

Page 38 432012

Hoffman JR Mower WR et al Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma N Engl J Med 200034394-99 Application of the NEXUS criteria

mohammad reza rajabi

Page 15 432012

View from the side

2 finger-breadths fit between the tip of the chin and the neck

Airway Examination

Mouth opening

Normal

Reduced

What is mouth opening

(normal)Incorrect

it is less than 3 finger breadths

mohammad reza rajabi

Page 16 432012

(reduced)Correct

The mouth opening is less than 3 finger-breadths

Open Mouth

The inter-incisor distance on maximal mouth opening Should be gt4 cm in an adult or 3-4 of the patients finger-breadths

This patients mouth opening is 2 finger breadths the soft palate is barely visible on maximal mouth opening

Mallampati Score

I

II

III

IV

What is Mallampati Score

mohammad reza rajabi

Page 17 432012

(I)Incorrect

The uvula cannot be seen

(II)Incorrect

Not even the top of the uvula is visible

(III)Yes

All structures visible up to the soft palate is a Mallampati Class III

(IV)Incorrect

The soft palate is visible

Mentum-Hyoid distance

Normal

Reduced

What distance

(normal)Incorrect

3 finger-breadths is normal this patient has only 2

(reduced)Yes

this is less than the normal 3 finger-breadths

View from the side

2 finger-breadths fit between the tip of the chin and the neck

mohammad reza rajabi

Page 18 432012

Neck Extension

Normal

Reduced

What is neck extension

(normal)Correct

The neck extends

(reduced)Incorrect

The neck motion is gt 90 degrees

Neck

The range of motion should be more than 90deg Motion less than 80deg may triple the risk

of a poor view at laryngoscopy

Airway Evaluation Summary

Because of the reduced mentum-hyoid distance it may be difficult to visualize the larynx with traditional direct laryngoscopy There are

other options including other blades and techniques that do not require a direct line-of-sight which are beyond the scope of this site

Perhaps the most conservative method of securing the airway of a

patient who is anticipated to have a difficult airway is with awake

fiberoptic intubation This technique requires substantial skill but allows intubation in an awake spontaneously breathing patient The

trachea is identified with a flexible fiberscope and then the endotracheal tube is advanced over the fiberscope like a stylet Such

mohammad reza rajabi

Page 19 432012

a procedure requires blockade of the sensory innervation to the

airway and blunting of the gag reflex

Innervation of the Upper Airway

Awake fiberoptic intubation requires topical anesthesia for patient

comfort as well as to blunt the gag reflex that would prevent successful intubation of the trachea

Several nerves are involved in the sensation of the upper airway

Anterior 23 of the tongue - Trigeminal nerve (V)

Posterior 13 of tongue to epiglottis - Glossopharyngeal nerve (IX afferent limb of gag reflex)

Epiglottis to vocal cords - Internal branch of Superior Laryngeal Nerve (Vagus X)

mohammad reza rajabi

Page 20 432012

Trachea below vocal cords - Recurrent Laryngeal Nerve

(Vagus X)

MOTOR INNERVATION

Motor innervation to the larynx is provided by the Vagus Nerve but recall there are two branches involved The Recurrent Laryngeal

Nerve innervates all the muscles of the larynx EXCEPT the

cricothyroid muscle which is innervated by the External Branch of the Superior Laryngeal Nerve Because the function of the

cricothyroid muscle is to stretch and tense the vocal cords unopposed action of the cricothyroid as may occur with bilateral

destruction of the recurrent laryngeal nerves would lead to stridor respiratory distress and possibly airway obstruction

GAG REFLEX

So the sensory afferent limb of the gag reflex is the glossopharyngeal nerve (IX) while the motor efferent limb is the

Vagus (X)

Its not much of a mnemonic but I remember this as a variant of TGIF Thank God its Recurrent I know its lame perhaps just

lame enough to be memorable

Airway Blocks

Topical application of local anesthetics is usually sufficient for the tongue and oronasopharynx though glossopharyngeal blocks are

performed occasionally Blunting of the gag reflex requires Transtracheal (really translaryngeal) with or without bilateral

Superior Laryngeal Nerve blocks as shown below

mohammad reza rajabi

Page 21 432012

The superior laryngeal nerves are blocked by deposition of 1 lidocaine near where the nerves penetrate the thyrohyoid

membrane The transtracheal block is accomplished with 4 lidocaine injected directly into the tracheal lumen Often this block

alone coupled with nebulized or atomized lidocaine is sufficient for awake intubation

mohammad reza rajabi

Page 22 432012

Airway Structures

The right panel displays images seen during fiberoptic bronchoscopy The corresponding level on CT is displayed on the middle panel

Place the cursor over structures to learn their identity

mohammad reza rajabi

Page 23 432012

mohammad reza rajabi

Page 24 432012

Review of Airway Innervation

Lets review the innervation of the upper airway

mohammad reza rajabi

Page 25 432012

Purple

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(V)Yes

The maxillary branch (V2) supplies the nasal cavity and palate while the mandibular branch (V3) supplies the anterior 23 of the tongue

(IX)Incorrect

The glossopharyngeal nerve supplies sensation to the posterior 13

of the tongue and its overlying structures including the soft palate

(X)No

The vagus innervates the airway further distal

Green

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)Yes

The glossopharyngeal nerve supplies sensation to the posterior 13

of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(X)No

The vagus innervates the airway further distal

mohammad reza rajabi

Page 26 432012

Blue

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)No

The glossopharyngeal nerve supplies sensation to the posterior 13 of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(x)Yes but which branch

Internal branch of superior laryngeal

External branch of superior laryngeal

Recurrent laryngeal

(Yes

The Internal Branch of the Superior Laryngeal Nerve provides

sensory innervation to the mucous membrane from the epiglottis to

and including the vocal cords

Incorrect

The External Branch of the Superior Laryngeal nerve provides motor innervation to the cricothyroid muscle only

Incorrect

The Recurrent Laryngeal Nerve supplies sensory innervation to the

trachea below the vocal cords as well as motor innervation to all the

intrinsic muscles of the larynx except the cricothyroid muscle)

mohammad reza rajabi

Page 27 432012

Red

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)No

The glossopharyngeal nerve supplies sensation to the posterior 13 of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(x)Yes but which branch

Internal branch of superior laryngeal

External branch of superior laryngeal

Recurrent laryngeal

(Incorrect

The Internal Branch of the Superior Laryngeal Nerve provides sensory innervation to the mucous membrane from the epiglottis to

and including the vocal cords

Incorrect

The External Branch of the Superior Laryngeal nerve provides motor innervation to the cricothyroid muscle only

Yes

The Recurrent Laryngeal Nerve supplies sensory innervation to the

trachea below the vocal cords as well as motor innervation to all the

intrinsic muscles of the larynx except the cricothyroid muscle)

mohammad reza rajabi

Page 28 432012

Case 3 Spine Evaluation

A previously healthy 40-year-old male presents with an open femur fracture from a Motor Vehicle Accident (MVA) that needs to be

repaired under general anesthesia He is currently on a backboard

with a cervical collar in place and is hemodynamically stable

Examination of this patients airway is complicated by the presence of the cervical collar which both inhibits mouth opening and by

definition prevents neck extension As you have seen above neck extension is required for direct laryngoscopy

So what shall we do

Remove the neck collar and intubate as usual

Intubate with a technique that does not require neck movement

Avoid general anesthesia and perform a regional block for the

procedure

Perform studies to clear the cervical spine

First a basic review of the anatomy is helpful

Recall that the cervical spine consists of 7 vertebrae the first two of

which are highly specialized

(Should this patient have an unstable cervical spine the movement resulting from laryngoscopy could permanently damage the spinal

cord likely resulting in quadriplegia)

(There are numerous techniques (retrograde intubationhellip) purported

to involve less cervical spine motion each of which requires substantial skill and experience These should only be attempted by

experienced practitioners Some advocate in-line stabilization where a second person attempts to hold the cervical spine still while

the primary person attempts direct laryngoscopy This technique makes intubation more difficult and is inadequate for stabilization)

mohammad reza rajabi

Page 29 432012

(While an attractive option many would argue that anytime a

regional anesthetic is planned immediate endotracheal intubation must be possible Complications may occur during the regional block

or it may be inadequate for the operation or wear off before the surgeons are done Therefore inability to emergently intubate a

patient is a relative contraindication to regional anesthesia and should be considered in this patient with a possible unstable neck)

(Great idea)

Cervical Spine Anatomy-Atlas

C1 The Atlas is a ring that interacts with the skull base above and

C2 shown on next page It is unique in that it lacks a vertebral body and spinous process The articulation of C1 with the occiput is very

tight providing little of the flexion of the cervical spine and only about 20 degrees of extension

mohammad reza rajabi

Page 30 432012

Cervical Spine Anatomy-Axis

C2 The Axis has an unusual thumb-like extension of its vertebral body that passes through the arch of C1 This process is called the

dens or odontoid The odontoid process is normally held very tightly against the anterior arch of C1 by the transverse ligament

Meanwhile the spinal cord travels behind the odontoid within the

arch of C1

mohammad reza rajabi

Page 31 432012

Atlanto Axial Joint

This atlanto-axial joint provides the majority of the rotational motion of the cervical spine Meanwhile flexion and extension are primarily

accomplished at C2 and below and particularly between C4 and C6

Neck Movement with DL

What happens to the neck during direct laryngoscopy and

intubation

As you have seen the sniffing position involves neck flexion in the lower cervical spine with extension superiorly In the process of

direct laryngoscopy this motion is accentuated As the laryngoscope

is lifted upward the occiput is extended primarily at the atlanto-occipital joint (occiput-C1) while flexion occurs at C2-3 and below

Therefore any intervention that impedes this flexion and extension

will make visualization of the glottis more difficult In someone with a cervical fusion up to the occiput it is pretty much impossible to

perform direct laryngoscopy Similarly a patient with external stabilization such as a c-collar in this case will (SHOULD) have neck

movement reduced sufficient to make visualization difficult if not impossible

mohammad reza rajabi

Page 32 432012

Clearing the C-Spine

How does one rule out damage to the cervical spine

At present history is our greatest ally If the healthy patient has no history of neck problems and no symptoms on maximal flexion and

extension they are unlikely to have cervical spine disease

On the other hand there are many patients whose cervical spine

SHOULD be radiographically evaluated pre-operatively including certain trauma patients as well as those with disease states that

affect the cervical spine including rheumatoid arthritis and Downs Syndrome These diseases may affect the transverse ligament and

thus the stability at the atlanto-axial joint

Nexus Criteria

Which trauma patients require cervical spine films prior to surgery or

intubation There is a set of criteria identified by the National Emergency X-

Radiography Utilization Study (NEXUS) that attempt to identify patients with a low probability of injury thereby reducing the

number of negative cervical spine radiographs taken

The criteria include No midline cervical tenderness

No focal neurologic deficit

Normal alertness

No intoxication

No painful distracting injury that might make them ignore their

neck pain

For those patients whose cervical spine is not cleared the

anesthesiologist must consider the risks of cervical spine damage that can be worsened through direct laryngoscopy versus the risk of

alternative techniques that may minimize neck motion including awake fiberoptic intubation A description of these alternate

techniques is beyond the scope of this site at present

mohammad reza rajabi

Page 33 432012

Spine Film

For the current case the following film is obtained

Patients Film

Normal for Comparison

mohammad reza rajabi

Page 34 432012

Explanation

Note the large step-off between C6 and C7 This subluxation causes entrapment of the spinal cord and damage

Therefore this patient requires an intubation technique with minimal neck motion and awake positioningas well as some external

stabilization or operative intervention to prevent damage to the spinal cord at the neck

mohammad reza rajabi

Page 35 432012

C-Spine Review

So which patients are at higher risk for neck injury during intubation

Trauma patients

Yes No

(yes)Correct

They may have trauma to the cervical spine as well

(no)Incorrect

They may have trauma to the cervical spine as well

Rheumatoid arthritis patients

Yes No

(yes)Correct

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

(no)Incorrect

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

Downs Syndrome patients

Yes No

(yes)Correct

About 15 of these patients have laxity in the transverse ligament

that holds the odontoid against the anterior arch of C1 Xrays are also recommended in these patients prior to anticipated neck

manipulation including laryngoscopy

mohammad reza rajabi

Page 36 432012

(no)Incorrect

About 15 of these patients have laxity in the transverse ligament that holds the odontoid against the anterior arch of C1 Xrays are

also recommended in these patients prior to anticipated neck manipulation including laryngoscopy

Osteoarthritic patients

Yes No

(yes)Incorrect

They are not at higher risk

(no)Correct

They are not at higher risk

Patient with a prior cervical spine fusion

Yes No

(yes)Incorrect

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

(no)Correct

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

mohammad reza rajabi

Page 37 432012

Airway References

Cricoid Pressure

Vanner RG Asai T Safe use of cricoid pressure Anaesthesia 1999 54 1-3 A review of literature with recommendations

Sellick BA Cricoid pressure to control regurgitation of stomach contents during induction of anaesthesia Lancet 1961 2 404-6 The original description

Views and Grades

Mallampati SR Gatt SP et al A clinical sign to predict difficult tracheal intubation a prospective study Can Anaesth Soc J 198532(4)429-434 The original paper describing the classification system but only 3 grades (III and IV combined)

Samsoon GLT and Young JRB Difficult tracheal intubation a retrospective study Anaesthesia 198742487-490 Describes the addition of Mallampati class 4

Cormack RS and Lehane J Difficult tracheal intubation in obstetrics Anaesthesia 1984391105-1111 Describes the laryngoscopy grades and correlates with difficult intubation Also proposes a technique of attempting to intubate while intentionally achieving a suboptimal (Class III) view

Studies of Predictive Indices

There are many studies some which counter others One difficulty is defining a difficult airway Most use a Cormack-Lehane laryngoscopy grade of III-IV Some investigate specific radiographic measurements that are impractical in daily clinical practice Below are a few useful references

El-Ganzouri AR McCarthy RJ et al Preoperative airway assessment Predictive value of a multivariate risk index Anesth Analg 1996821197-1204 A logistic regression comparing examination tests and developing a risk index

Chou HC Wu TL et al Mandibulohyoid distance in difficult laryngoscopy Br J Anaesth 1993 71335-339 A single article sighting this distance as an important factor in an analysis of only 11 patients

Frerk CM Predicting difficult intubation Anaesthesia 1991461005-1008 A study suggesting that a Mallampati Class III or IV with thyromental distance of lt7cm is sensitive and specific for difficult intubation (laryngoscopy grade 3 or 4)

C-Spine Evaluation

mohammad reza rajabi

Page 38 432012

Hoffman JR Mower WR et al Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma N Engl J Med 200034394-99 Application of the NEXUS criteria

mohammad reza rajabi

Page 16 432012

(reduced)Correct

The mouth opening is less than 3 finger-breadths

Open Mouth

The inter-incisor distance on maximal mouth opening Should be gt4 cm in an adult or 3-4 of the patients finger-breadths

This patients mouth opening is 2 finger breadths the soft palate is barely visible on maximal mouth opening

Mallampati Score

I

II

III

IV

What is Mallampati Score

mohammad reza rajabi

Page 17 432012

(I)Incorrect

The uvula cannot be seen

(II)Incorrect

Not even the top of the uvula is visible

(III)Yes

All structures visible up to the soft palate is a Mallampati Class III

(IV)Incorrect

The soft palate is visible

Mentum-Hyoid distance

Normal

Reduced

What distance

(normal)Incorrect

3 finger-breadths is normal this patient has only 2

(reduced)Yes

this is less than the normal 3 finger-breadths

View from the side

2 finger-breadths fit between the tip of the chin and the neck

mohammad reza rajabi

Page 18 432012

Neck Extension

Normal

Reduced

What is neck extension

(normal)Correct

The neck extends

(reduced)Incorrect

The neck motion is gt 90 degrees

Neck

The range of motion should be more than 90deg Motion less than 80deg may triple the risk

of a poor view at laryngoscopy

Airway Evaluation Summary

Because of the reduced mentum-hyoid distance it may be difficult to visualize the larynx with traditional direct laryngoscopy There are

other options including other blades and techniques that do not require a direct line-of-sight which are beyond the scope of this site

Perhaps the most conservative method of securing the airway of a

patient who is anticipated to have a difficult airway is with awake

fiberoptic intubation This technique requires substantial skill but allows intubation in an awake spontaneously breathing patient The

trachea is identified with a flexible fiberscope and then the endotracheal tube is advanced over the fiberscope like a stylet Such

mohammad reza rajabi

Page 19 432012

a procedure requires blockade of the sensory innervation to the

airway and blunting of the gag reflex

Innervation of the Upper Airway

Awake fiberoptic intubation requires topical anesthesia for patient

comfort as well as to blunt the gag reflex that would prevent successful intubation of the trachea

Several nerves are involved in the sensation of the upper airway

Anterior 23 of the tongue - Trigeminal nerve (V)

Posterior 13 of tongue to epiglottis - Glossopharyngeal nerve (IX afferent limb of gag reflex)

Epiglottis to vocal cords - Internal branch of Superior Laryngeal Nerve (Vagus X)

mohammad reza rajabi

Page 20 432012

Trachea below vocal cords - Recurrent Laryngeal Nerve

(Vagus X)

MOTOR INNERVATION

Motor innervation to the larynx is provided by the Vagus Nerve but recall there are two branches involved The Recurrent Laryngeal

Nerve innervates all the muscles of the larynx EXCEPT the

cricothyroid muscle which is innervated by the External Branch of the Superior Laryngeal Nerve Because the function of the

cricothyroid muscle is to stretch and tense the vocal cords unopposed action of the cricothyroid as may occur with bilateral

destruction of the recurrent laryngeal nerves would lead to stridor respiratory distress and possibly airway obstruction

GAG REFLEX

So the sensory afferent limb of the gag reflex is the glossopharyngeal nerve (IX) while the motor efferent limb is the

Vagus (X)

Its not much of a mnemonic but I remember this as a variant of TGIF Thank God its Recurrent I know its lame perhaps just

lame enough to be memorable

Airway Blocks

Topical application of local anesthetics is usually sufficient for the tongue and oronasopharynx though glossopharyngeal blocks are

performed occasionally Blunting of the gag reflex requires Transtracheal (really translaryngeal) with or without bilateral

Superior Laryngeal Nerve blocks as shown below

mohammad reza rajabi

Page 21 432012

The superior laryngeal nerves are blocked by deposition of 1 lidocaine near where the nerves penetrate the thyrohyoid

membrane The transtracheal block is accomplished with 4 lidocaine injected directly into the tracheal lumen Often this block

alone coupled with nebulized or atomized lidocaine is sufficient for awake intubation

mohammad reza rajabi

Page 22 432012

Airway Structures

The right panel displays images seen during fiberoptic bronchoscopy The corresponding level on CT is displayed on the middle panel

Place the cursor over structures to learn their identity

mohammad reza rajabi

Page 23 432012

mohammad reza rajabi

Page 24 432012

Review of Airway Innervation

Lets review the innervation of the upper airway

mohammad reza rajabi

Page 25 432012

Purple

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(V)Yes

The maxillary branch (V2) supplies the nasal cavity and palate while the mandibular branch (V3) supplies the anterior 23 of the tongue

(IX)Incorrect

The glossopharyngeal nerve supplies sensation to the posterior 13

of the tongue and its overlying structures including the soft palate

(X)No

The vagus innervates the airway further distal

Green

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)Yes

The glossopharyngeal nerve supplies sensation to the posterior 13

of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(X)No

The vagus innervates the airway further distal

mohammad reza rajabi

Page 26 432012

Blue

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)No

The glossopharyngeal nerve supplies sensation to the posterior 13 of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(x)Yes but which branch

Internal branch of superior laryngeal

External branch of superior laryngeal

Recurrent laryngeal

(Yes

The Internal Branch of the Superior Laryngeal Nerve provides

sensory innervation to the mucous membrane from the epiglottis to

and including the vocal cords

Incorrect

The External Branch of the Superior Laryngeal nerve provides motor innervation to the cricothyroid muscle only

Incorrect

The Recurrent Laryngeal Nerve supplies sensory innervation to the

trachea below the vocal cords as well as motor innervation to all the

intrinsic muscles of the larynx except the cricothyroid muscle)

mohammad reza rajabi

Page 27 432012

Red

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)No

The glossopharyngeal nerve supplies sensation to the posterior 13 of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(x)Yes but which branch

Internal branch of superior laryngeal

External branch of superior laryngeal

Recurrent laryngeal

(Incorrect

The Internal Branch of the Superior Laryngeal Nerve provides sensory innervation to the mucous membrane from the epiglottis to

and including the vocal cords

Incorrect

The External Branch of the Superior Laryngeal nerve provides motor innervation to the cricothyroid muscle only

Yes

The Recurrent Laryngeal Nerve supplies sensory innervation to the

trachea below the vocal cords as well as motor innervation to all the

intrinsic muscles of the larynx except the cricothyroid muscle)

mohammad reza rajabi

Page 28 432012

Case 3 Spine Evaluation

A previously healthy 40-year-old male presents with an open femur fracture from a Motor Vehicle Accident (MVA) that needs to be

repaired under general anesthesia He is currently on a backboard

with a cervical collar in place and is hemodynamically stable

Examination of this patients airway is complicated by the presence of the cervical collar which both inhibits mouth opening and by

definition prevents neck extension As you have seen above neck extension is required for direct laryngoscopy

So what shall we do

Remove the neck collar and intubate as usual

Intubate with a technique that does not require neck movement

Avoid general anesthesia and perform a regional block for the

procedure

Perform studies to clear the cervical spine

First a basic review of the anatomy is helpful

Recall that the cervical spine consists of 7 vertebrae the first two of

which are highly specialized

(Should this patient have an unstable cervical spine the movement resulting from laryngoscopy could permanently damage the spinal

cord likely resulting in quadriplegia)

(There are numerous techniques (retrograde intubationhellip) purported

to involve less cervical spine motion each of which requires substantial skill and experience These should only be attempted by

experienced practitioners Some advocate in-line stabilization where a second person attempts to hold the cervical spine still while

the primary person attempts direct laryngoscopy This technique makes intubation more difficult and is inadequate for stabilization)

mohammad reza rajabi

Page 29 432012

(While an attractive option many would argue that anytime a

regional anesthetic is planned immediate endotracheal intubation must be possible Complications may occur during the regional block

or it may be inadequate for the operation or wear off before the surgeons are done Therefore inability to emergently intubate a

patient is a relative contraindication to regional anesthesia and should be considered in this patient with a possible unstable neck)

(Great idea)

Cervical Spine Anatomy-Atlas

C1 The Atlas is a ring that interacts with the skull base above and

C2 shown on next page It is unique in that it lacks a vertebral body and spinous process The articulation of C1 with the occiput is very

tight providing little of the flexion of the cervical spine and only about 20 degrees of extension

mohammad reza rajabi

Page 30 432012

Cervical Spine Anatomy-Axis

C2 The Axis has an unusual thumb-like extension of its vertebral body that passes through the arch of C1 This process is called the

dens or odontoid The odontoid process is normally held very tightly against the anterior arch of C1 by the transverse ligament

Meanwhile the spinal cord travels behind the odontoid within the

arch of C1

mohammad reza rajabi

Page 31 432012

Atlanto Axial Joint

This atlanto-axial joint provides the majority of the rotational motion of the cervical spine Meanwhile flexion and extension are primarily

accomplished at C2 and below and particularly between C4 and C6

Neck Movement with DL

What happens to the neck during direct laryngoscopy and

intubation

As you have seen the sniffing position involves neck flexion in the lower cervical spine with extension superiorly In the process of

direct laryngoscopy this motion is accentuated As the laryngoscope

is lifted upward the occiput is extended primarily at the atlanto-occipital joint (occiput-C1) while flexion occurs at C2-3 and below

Therefore any intervention that impedes this flexion and extension

will make visualization of the glottis more difficult In someone with a cervical fusion up to the occiput it is pretty much impossible to

perform direct laryngoscopy Similarly a patient with external stabilization such as a c-collar in this case will (SHOULD) have neck

movement reduced sufficient to make visualization difficult if not impossible

mohammad reza rajabi

Page 32 432012

Clearing the C-Spine

How does one rule out damage to the cervical spine

At present history is our greatest ally If the healthy patient has no history of neck problems and no symptoms on maximal flexion and

extension they are unlikely to have cervical spine disease

On the other hand there are many patients whose cervical spine

SHOULD be radiographically evaluated pre-operatively including certain trauma patients as well as those with disease states that

affect the cervical spine including rheumatoid arthritis and Downs Syndrome These diseases may affect the transverse ligament and

thus the stability at the atlanto-axial joint

Nexus Criteria

Which trauma patients require cervical spine films prior to surgery or

intubation There is a set of criteria identified by the National Emergency X-

Radiography Utilization Study (NEXUS) that attempt to identify patients with a low probability of injury thereby reducing the

number of negative cervical spine radiographs taken

The criteria include No midline cervical tenderness

No focal neurologic deficit

Normal alertness

No intoxication

No painful distracting injury that might make them ignore their

neck pain

For those patients whose cervical spine is not cleared the

anesthesiologist must consider the risks of cervical spine damage that can be worsened through direct laryngoscopy versus the risk of

alternative techniques that may minimize neck motion including awake fiberoptic intubation A description of these alternate

techniques is beyond the scope of this site at present

mohammad reza rajabi

Page 33 432012

Spine Film

For the current case the following film is obtained

Patients Film

Normal for Comparison

mohammad reza rajabi

Page 34 432012

Explanation

Note the large step-off between C6 and C7 This subluxation causes entrapment of the spinal cord and damage

Therefore this patient requires an intubation technique with minimal neck motion and awake positioningas well as some external

stabilization or operative intervention to prevent damage to the spinal cord at the neck

mohammad reza rajabi

Page 35 432012

C-Spine Review

So which patients are at higher risk for neck injury during intubation

Trauma patients

Yes No

(yes)Correct

They may have trauma to the cervical spine as well

(no)Incorrect

They may have trauma to the cervical spine as well

Rheumatoid arthritis patients

Yes No

(yes)Correct

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

(no)Incorrect

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

Downs Syndrome patients

Yes No

(yes)Correct

About 15 of these patients have laxity in the transverse ligament

that holds the odontoid against the anterior arch of C1 Xrays are also recommended in these patients prior to anticipated neck

manipulation including laryngoscopy

mohammad reza rajabi

Page 36 432012

(no)Incorrect

About 15 of these patients have laxity in the transverse ligament that holds the odontoid against the anterior arch of C1 Xrays are

also recommended in these patients prior to anticipated neck manipulation including laryngoscopy

Osteoarthritic patients

Yes No

(yes)Incorrect

They are not at higher risk

(no)Correct

They are not at higher risk

Patient with a prior cervical spine fusion

Yes No

(yes)Incorrect

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

(no)Correct

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

mohammad reza rajabi

Page 37 432012

Airway References

Cricoid Pressure

Vanner RG Asai T Safe use of cricoid pressure Anaesthesia 1999 54 1-3 A review of literature with recommendations

Sellick BA Cricoid pressure to control regurgitation of stomach contents during induction of anaesthesia Lancet 1961 2 404-6 The original description

Views and Grades

Mallampati SR Gatt SP et al A clinical sign to predict difficult tracheal intubation a prospective study Can Anaesth Soc J 198532(4)429-434 The original paper describing the classification system but only 3 grades (III and IV combined)

Samsoon GLT and Young JRB Difficult tracheal intubation a retrospective study Anaesthesia 198742487-490 Describes the addition of Mallampati class 4

Cormack RS and Lehane J Difficult tracheal intubation in obstetrics Anaesthesia 1984391105-1111 Describes the laryngoscopy grades and correlates with difficult intubation Also proposes a technique of attempting to intubate while intentionally achieving a suboptimal (Class III) view

Studies of Predictive Indices

There are many studies some which counter others One difficulty is defining a difficult airway Most use a Cormack-Lehane laryngoscopy grade of III-IV Some investigate specific radiographic measurements that are impractical in daily clinical practice Below are a few useful references

El-Ganzouri AR McCarthy RJ et al Preoperative airway assessment Predictive value of a multivariate risk index Anesth Analg 1996821197-1204 A logistic regression comparing examination tests and developing a risk index

Chou HC Wu TL et al Mandibulohyoid distance in difficult laryngoscopy Br J Anaesth 1993 71335-339 A single article sighting this distance as an important factor in an analysis of only 11 patients

Frerk CM Predicting difficult intubation Anaesthesia 1991461005-1008 A study suggesting that a Mallampati Class III or IV with thyromental distance of lt7cm is sensitive and specific for difficult intubation (laryngoscopy grade 3 or 4)

C-Spine Evaluation

mohammad reza rajabi

Page 38 432012

Hoffman JR Mower WR et al Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma N Engl J Med 200034394-99 Application of the NEXUS criteria

mohammad reza rajabi

Page 17 432012

(I)Incorrect

The uvula cannot be seen

(II)Incorrect

Not even the top of the uvula is visible

(III)Yes

All structures visible up to the soft palate is a Mallampati Class III

(IV)Incorrect

The soft palate is visible

Mentum-Hyoid distance

Normal

Reduced

What distance

(normal)Incorrect

3 finger-breadths is normal this patient has only 2

(reduced)Yes

this is less than the normal 3 finger-breadths

View from the side

2 finger-breadths fit between the tip of the chin and the neck

mohammad reza rajabi

Page 18 432012

Neck Extension

Normal

Reduced

What is neck extension

(normal)Correct

The neck extends

(reduced)Incorrect

The neck motion is gt 90 degrees

Neck

The range of motion should be more than 90deg Motion less than 80deg may triple the risk

of a poor view at laryngoscopy

Airway Evaluation Summary

Because of the reduced mentum-hyoid distance it may be difficult to visualize the larynx with traditional direct laryngoscopy There are

other options including other blades and techniques that do not require a direct line-of-sight which are beyond the scope of this site

Perhaps the most conservative method of securing the airway of a

patient who is anticipated to have a difficult airway is with awake

fiberoptic intubation This technique requires substantial skill but allows intubation in an awake spontaneously breathing patient The

trachea is identified with a flexible fiberscope and then the endotracheal tube is advanced over the fiberscope like a stylet Such

mohammad reza rajabi

Page 19 432012

a procedure requires blockade of the sensory innervation to the

airway and blunting of the gag reflex

Innervation of the Upper Airway

Awake fiberoptic intubation requires topical anesthesia for patient

comfort as well as to blunt the gag reflex that would prevent successful intubation of the trachea

Several nerves are involved in the sensation of the upper airway

Anterior 23 of the tongue - Trigeminal nerve (V)

Posterior 13 of tongue to epiglottis - Glossopharyngeal nerve (IX afferent limb of gag reflex)

Epiglottis to vocal cords - Internal branch of Superior Laryngeal Nerve (Vagus X)

mohammad reza rajabi

Page 20 432012

Trachea below vocal cords - Recurrent Laryngeal Nerve

(Vagus X)

MOTOR INNERVATION

Motor innervation to the larynx is provided by the Vagus Nerve but recall there are two branches involved The Recurrent Laryngeal

Nerve innervates all the muscles of the larynx EXCEPT the

cricothyroid muscle which is innervated by the External Branch of the Superior Laryngeal Nerve Because the function of the

cricothyroid muscle is to stretch and tense the vocal cords unopposed action of the cricothyroid as may occur with bilateral

destruction of the recurrent laryngeal nerves would lead to stridor respiratory distress and possibly airway obstruction

GAG REFLEX

So the sensory afferent limb of the gag reflex is the glossopharyngeal nerve (IX) while the motor efferent limb is the

Vagus (X)

Its not much of a mnemonic but I remember this as a variant of TGIF Thank God its Recurrent I know its lame perhaps just

lame enough to be memorable

Airway Blocks

Topical application of local anesthetics is usually sufficient for the tongue and oronasopharynx though glossopharyngeal blocks are

performed occasionally Blunting of the gag reflex requires Transtracheal (really translaryngeal) with or without bilateral

Superior Laryngeal Nerve blocks as shown below

mohammad reza rajabi

Page 21 432012

The superior laryngeal nerves are blocked by deposition of 1 lidocaine near where the nerves penetrate the thyrohyoid

membrane The transtracheal block is accomplished with 4 lidocaine injected directly into the tracheal lumen Often this block

alone coupled with nebulized or atomized lidocaine is sufficient for awake intubation

mohammad reza rajabi

Page 22 432012

Airway Structures

The right panel displays images seen during fiberoptic bronchoscopy The corresponding level on CT is displayed on the middle panel

Place the cursor over structures to learn their identity

mohammad reza rajabi

Page 23 432012

mohammad reza rajabi

Page 24 432012

Review of Airway Innervation

Lets review the innervation of the upper airway

mohammad reza rajabi

Page 25 432012

Purple

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(V)Yes

The maxillary branch (V2) supplies the nasal cavity and palate while the mandibular branch (V3) supplies the anterior 23 of the tongue

(IX)Incorrect

The glossopharyngeal nerve supplies sensation to the posterior 13

of the tongue and its overlying structures including the soft palate

(X)No

The vagus innervates the airway further distal

Green

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)Yes

The glossopharyngeal nerve supplies sensation to the posterior 13

of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(X)No

The vagus innervates the airway further distal

mohammad reza rajabi

Page 26 432012

Blue

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)No

The glossopharyngeal nerve supplies sensation to the posterior 13 of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(x)Yes but which branch

Internal branch of superior laryngeal

External branch of superior laryngeal

Recurrent laryngeal

(Yes

The Internal Branch of the Superior Laryngeal Nerve provides

sensory innervation to the mucous membrane from the epiglottis to

and including the vocal cords

Incorrect

The External Branch of the Superior Laryngeal nerve provides motor innervation to the cricothyroid muscle only

Incorrect

The Recurrent Laryngeal Nerve supplies sensory innervation to the

trachea below the vocal cords as well as motor innervation to all the

intrinsic muscles of the larynx except the cricothyroid muscle)

mohammad reza rajabi

Page 27 432012

Red

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)No

The glossopharyngeal nerve supplies sensation to the posterior 13 of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(x)Yes but which branch

Internal branch of superior laryngeal

External branch of superior laryngeal

Recurrent laryngeal

(Incorrect

The Internal Branch of the Superior Laryngeal Nerve provides sensory innervation to the mucous membrane from the epiglottis to

and including the vocal cords

Incorrect

The External Branch of the Superior Laryngeal nerve provides motor innervation to the cricothyroid muscle only

Yes

The Recurrent Laryngeal Nerve supplies sensory innervation to the

trachea below the vocal cords as well as motor innervation to all the

intrinsic muscles of the larynx except the cricothyroid muscle)

mohammad reza rajabi

Page 28 432012

Case 3 Spine Evaluation

A previously healthy 40-year-old male presents with an open femur fracture from a Motor Vehicle Accident (MVA) that needs to be

repaired under general anesthesia He is currently on a backboard

with a cervical collar in place and is hemodynamically stable

Examination of this patients airway is complicated by the presence of the cervical collar which both inhibits mouth opening and by

definition prevents neck extension As you have seen above neck extension is required for direct laryngoscopy

So what shall we do

Remove the neck collar and intubate as usual

Intubate with a technique that does not require neck movement

Avoid general anesthesia and perform a regional block for the

procedure

Perform studies to clear the cervical spine

First a basic review of the anatomy is helpful

Recall that the cervical spine consists of 7 vertebrae the first two of

which are highly specialized

(Should this patient have an unstable cervical spine the movement resulting from laryngoscopy could permanently damage the spinal

cord likely resulting in quadriplegia)

(There are numerous techniques (retrograde intubationhellip) purported

to involve less cervical spine motion each of which requires substantial skill and experience These should only be attempted by

experienced practitioners Some advocate in-line stabilization where a second person attempts to hold the cervical spine still while

the primary person attempts direct laryngoscopy This technique makes intubation more difficult and is inadequate for stabilization)

mohammad reza rajabi

Page 29 432012

(While an attractive option many would argue that anytime a

regional anesthetic is planned immediate endotracheal intubation must be possible Complications may occur during the regional block

or it may be inadequate for the operation or wear off before the surgeons are done Therefore inability to emergently intubate a

patient is a relative contraindication to regional anesthesia and should be considered in this patient with a possible unstable neck)

(Great idea)

Cervical Spine Anatomy-Atlas

C1 The Atlas is a ring that interacts with the skull base above and

C2 shown on next page It is unique in that it lacks a vertebral body and spinous process The articulation of C1 with the occiput is very

tight providing little of the flexion of the cervical spine and only about 20 degrees of extension

mohammad reza rajabi

Page 30 432012

Cervical Spine Anatomy-Axis

C2 The Axis has an unusual thumb-like extension of its vertebral body that passes through the arch of C1 This process is called the

dens or odontoid The odontoid process is normally held very tightly against the anterior arch of C1 by the transverse ligament

Meanwhile the spinal cord travels behind the odontoid within the

arch of C1

mohammad reza rajabi

Page 31 432012

Atlanto Axial Joint

This atlanto-axial joint provides the majority of the rotational motion of the cervical spine Meanwhile flexion and extension are primarily

accomplished at C2 and below and particularly between C4 and C6

Neck Movement with DL

What happens to the neck during direct laryngoscopy and

intubation

As you have seen the sniffing position involves neck flexion in the lower cervical spine with extension superiorly In the process of

direct laryngoscopy this motion is accentuated As the laryngoscope

is lifted upward the occiput is extended primarily at the atlanto-occipital joint (occiput-C1) while flexion occurs at C2-3 and below

Therefore any intervention that impedes this flexion and extension

will make visualization of the glottis more difficult In someone with a cervical fusion up to the occiput it is pretty much impossible to

perform direct laryngoscopy Similarly a patient with external stabilization such as a c-collar in this case will (SHOULD) have neck

movement reduced sufficient to make visualization difficult if not impossible

mohammad reza rajabi

Page 32 432012

Clearing the C-Spine

How does one rule out damage to the cervical spine

At present history is our greatest ally If the healthy patient has no history of neck problems and no symptoms on maximal flexion and

extension they are unlikely to have cervical spine disease

On the other hand there are many patients whose cervical spine

SHOULD be radiographically evaluated pre-operatively including certain trauma patients as well as those with disease states that

affect the cervical spine including rheumatoid arthritis and Downs Syndrome These diseases may affect the transverse ligament and

thus the stability at the atlanto-axial joint

Nexus Criteria

Which trauma patients require cervical spine films prior to surgery or

intubation There is a set of criteria identified by the National Emergency X-

Radiography Utilization Study (NEXUS) that attempt to identify patients with a low probability of injury thereby reducing the

number of negative cervical spine radiographs taken

The criteria include No midline cervical tenderness

No focal neurologic deficit

Normal alertness

No intoxication

No painful distracting injury that might make them ignore their

neck pain

For those patients whose cervical spine is not cleared the

anesthesiologist must consider the risks of cervical spine damage that can be worsened through direct laryngoscopy versus the risk of

alternative techniques that may minimize neck motion including awake fiberoptic intubation A description of these alternate

techniques is beyond the scope of this site at present

mohammad reza rajabi

Page 33 432012

Spine Film

For the current case the following film is obtained

Patients Film

Normal for Comparison

mohammad reza rajabi

Page 34 432012

Explanation

Note the large step-off between C6 and C7 This subluxation causes entrapment of the spinal cord and damage

Therefore this patient requires an intubation technique with minimal neck motion and awake positioningas well as some external

stabilization or operative intervention to prevent damage to the spinal cord at the neck

mohammad reza rajabi

Page 35 432012

C-Spine Review

So which patients are at higher risk for neck injury during intubation

Trauma patients

Yes No

(yes)Correct

They may have trauma to the cervical spine as well

(no)Incorrect

They may have trauma to the cervical spine as well

Rheumatoid arthritis patients

Yes No

(yes)Correct

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

(no)Incorrect

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

Downs Syndrome patients

Yes No

(yes)Correct

About 15 of these patients have laxity in the transverse ligament

that holds the odontoid against the anterior arch of C1 Xrays are also recommended in these patients prior to anticipated neck

manipulation including laryngoscopy

mohammad reza rajabi

Page 36 432012

(no)Incorrect

About 15 of these patients have laxity in the transverse ligament that holds the odontoid against the anterior arch of C1 Xrays are

also recommended in these patients prior to anticipated neck manipulation including laryngoscopy

Osteoarthritic patients

Yes No

(yes)Incorrect

They are not at higher risk

(no)Correct

They are not at higher risk

Patient with a prior cervical spine fusion

Yes No

(yes)Incorrect

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

(no)Correct

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

mohammad reza rajabi

Page 37 432012

Airway References

Cricoid Pressure

Vanner RG Asai T Safe use of cricoid pressure Anaesthesia 1999 54 1-3 A review of literature with recommendations

Sellick BA Cricoid pressure to control regurgitation of stomach contents during induction of anaesthesia Lancet 1961 2 404-6 The original description

Views and Grades

Mallampati SR Gatt SP et al A clinical sign to predict difficult tracheal intubation a prospective study Can Anaesth Soc J 198532(4)429-434 The original paper describing the classification system but only 3 grades (III and IV combined)

Samsoon GLT and Young JRB Difficult tracheal intubation a retrospective study Anaesthesia 198742487-490 Describes the addition of Mallampati class 4

Cormack RS and Lehane J Difficult tracheal intubation in obstetrics Anaesthesia 1984391105-1111 Describes the laryngoscopy grades and correlates with difficult intubation Also proposes a technique of attempting to intubate while intentionally achieving a suboptimal (Class III) view

Studies of Predictive Indices

There are many studies some which counter others One difficulty is defining a difficult airway Most use a Cormack-Lehane laryngoscopy grade of III-IV Some investigate specific radiographic measurements that are impractical in daily clinical practice Below are a few useful references

El-Ganzouri AR McCarthy RJ et al Preoperative airway assessment Predictive value of a multivariate risk index Anesth Analg 1996821197-1204 A logistic regression comparing examination tests and developing a risk index

Chou HC Wu TL et al Mandibulohyoid distance in difficult laryngoscopy Br J Anaesth 1993 71335-339 A single article sighting this distance as an important factor in an analysis of only 11 patients

Frerk CM Predicting difficult intubation Anaesthesia 1991461005-1008 A study suggesting that a Mallampati Class III or IV with thyromental distance of lt7cm is sensitive and specific for difficult intubation (laryngoscopy grade 3 or 4)

C-Spine Evaluation

mohammad reza rajabi

Page 38 432012

Hoffman JR Mower WR et al Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma N Engl J Med 200034394-99 Application of the NEXUS criteria

mohammad reza rajabi

Page 18 432012

Neck Extension

Normal

Reduced

What is neck extension

(normal)Correct

The neck extends

(reduced)Incorrect

The neck motion is gt 90 degrees

Neck

The range of motion should be more than 90deg Motion less than 80deg may triple the risk

of a poor view at laryngoscopy

Airway Evaluation Summary

Because of the reduced mentum-hyoid distance it may be difficult to visualize the larynx with traditional direct laryngoscopy There are

other options including other blades and techniques that do not require a direct line-of-sight which are beyond the scope of this site

Perhaps the most conservative method of securing the airway of a

patient who is anticipated to have a difficult airway is with awake

fiberoptic intubation This technique requires substantial skill but allows intubation in an awake spontaneously breathing patient The

trachea is identified with a flexible fiberscope and then the endotracheal tube is advanced over the fiberscope like a stylet Such

mohammad reza rajabi

Page 19 432012

a procedure requires blockade of the sensory innervation to the

airway and blunting of the gag reflex

Innervation of the Upper Airway

Awake fiberoptic intubation requires topical anesthesia for patient

comfort as well as to blunt the gag reflex that would prevent successful intubation of the trachea

Several nerves are involved in the sensation of the upper airway

Anterior 23 of the tongue - Trigeminal nerve (V)

Posterior 13 of tongue to epiglottis - Glossopharyngeal nerve (IX afferent limb of gag reflex)

Epiglottis to vocal cords - Internal branch of Superior Laryngeal Nerve (Vagus X)

mohammad reza rajabi

Page 20 432012

Trachea below vocal cords - Recurrent Laryngeal Nerve

(Vagus X)

MOTOR INNERVATION

Motor innervation to the larynx is provided by the Vagus Nerve but recall there are two branches involved The Recurrent Laryngeal

Nerve innervates all the muscles of the larynx EXCEPT the

cricothyroid muscle which is innervated by the External Branch of the Superior Laryngeal Nerve Because the function of the

cricothyroid muscle is to stretch and tense the vocal cords unopposed action of the cricothyroid as may occur with bilateral

destruction of the recurrent laryngeal nerves would lead to stridor respiratory distress and possibly airway obstruction

GAG REFLEX

So the sensory afferent limb of the gag reflex is the glossopharyngeal nerve (IX) while the motor efferent limb is the

Vagus (X)

Its not much of a mnemonic but I remember this as a variant of TGIF Thank God its Recurrent I know its lame perhaps just

lame enough to be memorable

Airway Blocks

Topical application of local anesthetics is usually sufficient for the tongue and oronasopharynx though glossopharyngeal blocks are

performed occasionally Blunting of the gag reflex requires Transtracheal (really translaryngeal) with or without bilateral

Superior Laryngeal Nerve blocks as shown below

mohammad reza rajabi

Page 21 432012

The superior laryngeal nerves are blocked by deposition of 1 lidocaine near where the nerves penetrate the thyrohyoid

membrane The transtracheal block is accomplished with 4 lidocaine injected directly into the tracheal lumen Often this block

alone coupled with nebulized or atomized lidocaine is sufficient for awake intubation

mohammad reza rajabi

Page 22 432012

Airway Structures

The right panel displays images seen during fiberoptic bronchoscopy The corresponding level on CT is displayed on the middle panel

Place the cursor over structures to learn their identity

mohammad reza rajabi

Page 23 432012

mohammad reza rajabi

Page 24 432012

Review of Airway Innervation

Lets review the innervation of the upper airway

mohammad reza rajabi

Page 25 432012

Purple

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(V)Yes

The maxillary branch (V2) supplies the nasal cavity and palate while the mandibular branch (V3) supplies the anterior 23 of the tongue

(IX)Incorrect

The glossopharyngeal nerve supplies sensation to the posterior 13

of the tongue and its overlying structures including the soft palate

(X)No

The vagus innervates the airway further distal

Green

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)Yes

The glossopharyngeal nerve supplies sensation to the posterior 13

of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(X)No

The vagus innervates the airway further distal

mohammad reza rajabi

Page 26 432012

Blue

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)No

The glossopharyngeal nerve supplies sensation to the posterior 13 of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(x)Yes but which branch

Internal branch of superior laryngeal

External branch of superior laryngeal

Recurrent laryngeal

(Yes

The Internal Branch of the Superior Laryngeal Nerve provides

sensory innervation to the mucous membrane from the epiglottis to

and including the vocal cords

Incorrect

The External Branch of the Superior Laryngeal nerve provides motor innervation to the cricothyroid muscle only

Incorrect

The Recurrent Laryngeal Nerve supplies sensory innervation to the

trachea below the vocal cords as well as motor innervation to all the

intrinsic muscles of the larynx except the cricothyroid muscle)

mohammad reza rajabi

Page 27 432012

Red

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)No

The glossopharyngeal nerve supplies sensation to the posterior 13 of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(x)Yes but which branch

Internal branch of superior laryngeal

External branch of superior laryngeal

Recurrent laryngeal

(Incorrect

The Internal Branch of the Superior Laryngeal Nerve provides sensory innervation to the mucous membrane from the epiglottis to

and including the vocal cords

Incorrect

The External Branch of the Superior Laryngeal nerve provides motor innervation to the cricothyroid muscle only

Yes

The Recurrent Laryngeal Nerve supplies sensory innervation to the

trachea below the vocal cords as well as motor innervation to all the

intrinsic muscles of the larynx except the cricothyroid muscle)

mohammad reza rajabi

Page 28 432012

Case 3 Spine Evaluation

A previously healthy 40-year-old male presents with an open femur fracture from a Motor Vehicle Accident (MVA) that needs to be

repaired under general anesthesia He is currently on a backboard

with a cervical collar in place and is hemodynamically stable

Examination of this patients airway is complicated by the presence of the cervical collar which both inhibits mouth opening and by

definition prevents neck extension As you have seen above neck extension is required for direct laryngoscopy

So what shall we do

Remove the neck collar and intubate as usual

Intubate with a technique that does not require neck movement

Avoid general anesthesia and perform a regional block for the

procedure

Perform studies to clear the cervical spine

First a basic review of the anatomy is helpful

Recall that the cervical spine consists of 7 vertebrae the first two of

which are highly specialized

(Should this patient have an unstable cervical spine the movement resulting from laryngoscopy could permanently damage the spinal

cord likely resulting in quadriplegia)

(There are numerous techniques (retrograde intubationhellip) purported

to involve less cervical spine motion each of which requires substantial skill and experience These should only be attempted by

experienced practitioners Some advocate in-line stabilization where a second person attempts to hold the cervical spine still while

the primary person attempts direct laryngoscopy This technique makes intubation more difficult and is inadequate for stabilization)

mohammad reza rajabi

Page 29 432012

(While an attractive option many would argue that anytime a

regional anesthetic is planned immediate endotracheal intubation must be possible Complications may occur during the regional block

or it may be inadequate for the operation or wear off before the surgeons are done Therefore inability to emergently intubate a

patient is a relative contraindication to regional anesthesia and should be considered in this patient with a possible unstable neck)

(Great idea)

Cervical Spine Anatomy-Atlas

C1 The Atlas is a ring that interacts with the skull base above and

C2 shown on next page It is unique in that it lacks a vertebral body and spinous process The articulation of C1 with the occiput is very

tight providing little of the flexion of the cervical spine and only about 20 degrees of extension

mohammad reza rajabi

Page 30 432012

Cervical Spine Anatomy-Axis

C2 The Axis has an unusual thumb-like extension of its vertebral body that passes through the arch of C1 This process is called the

dens or odontoid The odontoid process is normally held very tightly against the anterior arch of C1 by the transverse ligament

Meanwhile the spinal cord travels behind the odontoid within the

arch of C1

mohammad reza rajabi

Page 31 432012

Atlanto Axial Joint

This atlanto-axial joint provides the majority of the rotational motion of the cervical spine Meanwhile flexion and extension are primarily

accomplished at C2 and below and particularly between C4 and C6

Neck Movement with DL

What happens to the neck during direct laryngoscopy and

intubation

As you have seen the sniffing position involves neck flexion in the lower cervical spine with extension superiorly In the process of

direct laryngoscopy this motion is accentuated As the laryngoscope

is lifted upward the occiput is extended primarily at the atlanto-occipital joint (occiput-C1) while flexion occurs at C2-3 and below

Therefore any intervention that impedes this flexion and extension

will make visualization of the glottis more difficult In someone with a cervical fusion up to the occiput it is pretty much impossible to

perform direct laryngoscopy Similarly a patient with external stabilization such as a c-collar in this case will (SHOULD) have neck

movement reduced sufficient to make visualization difficult if not impossible

mohammad reza rajabi

Page 32 432012

Clearing the C-Spine

How does one rule out damage to the cervical spine

At present history is our greatest ally If the healthy patient has no history of neck problems and no symptoms on maximal flexion and

extension they are unlikely to have cervical spine disease

On the other hand there are many patients whose cervical spine

SHOULD be radiographically evaluated pre-operatively including certain trauma patients as well as those with disease states that

affect the cervical spine including rheumatoid arthritis and Downs Syndrome These diseases may affect the transverse ligament and

thus the stability at the atlanto-axial joint

Nexus Criteria

Which trauma patients require cervical spine films prior to surgery or

intubation There is a set of criteria identified by the National Emergency X-

Radiography Utilization Study (NEXUS) that attempt to identify patients with a low probability of injury thereby reducing the

number of negative cervical spine radiographs taken

The criteria include No midline cervical tenderness

No focal neurologic deficit

Normal alertness

No intoxication

No painful distracting injury that might make them ignore their

neck pain

For those patients whose cervical spine is not cleared the

anesthesiologist must consider the risks of cervical spine damage that can be worsened through direct laryngoscopy versus the risk of

alternative techniques that may minimize neck motion including awake fiberoptic intubation A description of these alternate

techniques is beyond the scope of this site at present

mohammad reza rajabi

Page 33 432012

Spine Film

For the current case the following film is obtained

Patients Film

Normal for Comparison

mohammad reza rajabi

Page 34 432012

Explanation

Note the large step-off between C6 and C7 This subluxation causes entrapment of the spinal cord and damage

Therefore this patient requires an intubation technique with minimal neck motion and awake positioningas well as some external

stabilization or operative intervention to prevent damage to the spinal cord at the neck

mohammad reza rajabi

Page 35 432012

C-Spine Review

So which patients are at higher risk for neck injury during intubation

Trauma patients

Yes No

(yes)Correct

They may have trauma to the cervical spine as well

(no)Incorrect

They may have trauma to the cervical spine as well

Rheumatoid arthritis patients

Yes No

(yes)Correct

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

(no)Incorrect

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

Downs Syndrome patients

Yes No

(yes)Correct

About 15 of these patients have laxity in the transverse ligament

that holds the odontoid against the anterior arch of C1 Xrays are also recommended in these patients prior to anticipated neck

manipulation including laryngoscopy

mohammad reza rajabi

Page 36 432012

(no)Incorrect

About 15 of these patients have laxity in the transverse ligament that holds the odontoid against the anterior arch of C1 Xrays are

also recommended in these patients prior to anticipated neck manipulation including laryngoscopy

Osteoarthritic patients

Yes No

(yes)Incorrect

They are not at higher risk

(no)Correct

They are not at higher risk

Patient with a prior cervical spine fusion

Yes No

(yes)Incorrect

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

(no)Correct

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

mohammad reza rajabi

Page 37 432012

Airway References

Cricoid Pressure

Vanner RG Asai T Safe use of cricoid pressure Anaesthesia 1999 54 1-3 A review of literature with recommendations

Sellick BA Cricoid pressure to control regurgitation of stomach contents during induction of anaesthesia Lancet 1961 2 404-6 The original description

Views and Grades

Mallampati SR Gatt SP et al A clinical sign to predict difficult tracheal intubation a prospective study Can Anaesth Soc J 198532(4)429-434 The original paper describing the classification system but only 3 grades (III and IV combined)

Samsoon GLT and Young JRB Difficult tracheal intubation a retrospective study Anaesthesia 198742487-490 Describes the addition of Mallampati class 4

Cormack RS and Lehane J Difficult tracheal intubation in obstetrics Anaesthesia 1984391105-1111 Describes the laryngoscopy grades and correlates with difficult intubation Also proposes a technique of attempting to intubate while intentionally achieving a suboptimal (Class III) view

Studies of Predictive Indices

There are many studies some which counter others One difficulty is defining a difficult airway Most use a Cormack-Lehane laryngoscopy grade of III-IV Some investigate specific radiographic measurements that are impractical in daily clinical practice Below are a few useful references

El-Ganzouri AR McCarthy RJ et al Preoperative airway assessment Predictive value of a multivariate risk index Anesth Analg 1996821197-1204 A logistic regression comparing examination tests and developing a risk index

Chou HC Wu TL et al Mandibulohyoid distance in difficult laryngoscopy Br J Anaesth 1993 71335-339 A single article sighting this distance as an important factor in an analysis of only 11 patients

Frerk CM Predicting difficult intubation Anaesthesia 1991461005-1008 A study suggesting that a Mallampati Class III or IV with thyromental distance of lt7cm is sensitive and specific for difficult intubation (laryngoscopy grade 3 or 4)

C-Spine Evaluation

mohammad reza rajabi

Page 38 432012

Hoffman JR Mower WR et al Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma N Engl J Med 200034394-99 Application of the NEXUS criteria

mohammad reza rajabi

Page 19 432012

a procedure requires blockade of the sensory innervation to the

airway and blunting of the gag reflex

Innervation of the Upper Airway

Awake fiberoptic intubation requires topical anesthesia for patient

comfort as well as to blunt the gag reflex that would prevent successful intubation of the trachea

Several nerves are involved in the sensation of the upper airway

Anterior 23 of the tongue - Trigeminal nerve (V)

Posterior 13 of tongue to epiglottis - Glossopharyngeal nerve (IX afferent limb of gag reflex)

Epiglottis to vocal cords - Internal branch of Superior Laryngeal Nerve (Vagus X)

mohammad reza rajabi

Page 20 432012

Trachea below vocal cords - Recurrent Laryngeal Nerve

(Vagus X)

MOTOR INNERVATION

Motor innervation to the larynx is provided by the Vagus Nerve but recall there are two branches involved The Recurrent Laryngeal

Nerve innervates all the muscles of the larynx EXCEPT the

cricothyroid muscle which is innervated by the External Branch of the Superior Laryngeal Nerve Because the function of the

cricothyroid muscle is to stretch and tense the vocal cords unopposed action of the cricothyroid as may occur with bilateral

destruction of the recurrent laryngeal nerves would lead to stridor respiratory distress and possibly airway obstruction

GAG REFLEX

So the sensory afferent limb of the gag reflex is the glossopharyngeal nerve (IX) while the motor efferent limb is the

Vagus (X)

Its not much of a mnemonic but I remember this as a variant of TGIF Thank God its Recurrent I know its lame perhaps just

lame enough to be memorable

Airway Blocks

Topical application of local anesthetics is usually sufficient for the tongue and oronasopharynx though glossopharyngeal blocks are

performed occasionally Blunting of the gag reflex requires Transtracheal (really translaryngeal) with or without bilateral

Superior Laryngeal Nerve blocks as shown below

mohammad reza rajabi

Page 21 432012

The superior laryngeal nerves are blocked by deposition of 1 lidocaine near where the nerves penetrate the thyrohyoid

membrane The transtracheal block is accomplished with 4 lidocaine injected directly into the tracheal lumen Often this block

alone coupled with nebulized or atomized lidocaine is sufficient for awake intubation

mohammad reza rajabi

Page 22 432012

Airway Structures

The right panel displays images seen during fiberoptic bronchoscopy The corresponding level on CT is displayed on the middle panel

Place the cursor over structures to learn their identity

mohammad reza rajabi

Page 23 432012

mohammad reza rajabi

Page 24 432012

Review of Airway Innervation

Lets review the innervation of the upper airway

mohammad reza rajabi

Page 25 432012

Purple

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(V)Yes

The maxillary branch (V2) supplies the nasal cavity and palate while the mandibular branch (V3) supplies the anterior 23 of the tongue

(IX)Incorrect

The glossopharyngeal nerve supplies sensation to the posterior 13

of the tongue and its overlying structures including the soft palate

(X)No

The vagus innervates the airway further distal

Green

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)Yes

The glossopharyngeal nerve supplies sensation to the posterior 13

of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(X)No

The vagus innervates the airway further distal

mohammad reza rajabi

Page 26 432012

Blue

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)No

The glossopharyngeal nerve supplies sensation to the posterior 13 of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(x)Yes but which branch

Internal branch of superior laryngeal

External branch of superior laryngeal

Recurrent laryngeal

(Yes

The Internal Branch of the Superior Laryngeal Nerve provides

sensory innervation to the mucous membrane from the epiglottis to

and including the vocal cords

Incorrect

The External Branch of the Superior Laryngeal nerve provides motor innervation to the cricothyroid muscle only

Incorrect

The Recurrent Laryngeal Nerve supplies sensory innervation to the

trachea below the vocal cords as well as motor innervation to all the

intrinsic muscles of the larynx except the cricothyroid muscle)

mohammad reza rajabi

Page 27 432012

Red

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)No

The glossopharyngeal nerve supplies sensation to the posterior 13 of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(x)Yes but which branch

Internal branch of superior laryngeal

External branch of superior laryngeal

Recurrent laryngeal

(Incorrect

The Internal Branch of the Superior Laryngeal Nerve provides sensory innervation to the mucous membrane from the epiglottis to

and including the vocal cords

Incorrect

The External Branch of the Superior Laryngeal nerve provides motor innervation to the cricothyroid muscle only

Yes

The Recurrent Laryngeal Nerve supplies sensory innervation to the

trachea below the vocal cords as well as motor innervation to all the

intrinsic muscles of the larynx except the cricothyroid muscle)

mohammad reza rajabi

Page 28 432012

Case 3 Spine Evaluation

A previously healthy 40-year-old male presents with an open femur fracture from a Motor Vehicle Accident (MVA) that needs to be

repaired under general anesthesia He is currently on a backboard

with a cervical collar in place and is hemodynamically stable

Examination of this patients airway is complicated by the presence of the cervical collar which both inhibits mouth opening and by

definition prevents neck extension As you have seen above neck extension is required for direct laryngoscopy

So what shall we do

Remove the neck collar and intubate as usual

Intubate with a technique that does not require neck movement

Avoid general anesthesia and perform a regional block for the

procedure

Perform studies to clear the cervical spine

First a basic review of the anatomy is helpful

Recall that the cervical spine consists of 7 vertebrae the first two of

which are highly specialized

(Should this patient have an unstable cervical spine the movement resulting from laryngoscopy could permanently damage the spinal

cord likely resulting in quadriplegia)

(There are numerous techniques (retrograde intubationhellip) purported

to involve less cervical spine motion each of which requires substantial skill and experience These should only be attempted by

experienced practitioners Some advocate in-line stabilization where a second person attempts to hold the cervical spine still while

the primary person attempts direct laryngoscopy This technique makes intubation more difficult and is inadequate for stabilization)

mohammad reza rajabi

Page 29 432012

(While an attractive option many would argue that anytime a

regional anesthetic is planned immediate endotracheal intubation must be possible Complications may occur during the regional block

or it may be inadequate for the operation or wear off before the surgeons are done Therefore inability to emergently intubate a

patient is a relative contraindication to regional anesthesia and should be considered in this patient with a possible unstable neck)

(Great idea)

Cervical Spine Anatomy-Atlas

C1 The Atlas is a ring that interacts with the skull base above and

C2 shown on next page It is unique in that it lacks a vertebral body and spinous process The articulation of C1 with the occiput is very

tight providing little of the flexion of the cervical spine and only about 20 degrees of extension

mohammad reza rajabi

Page 30 432012

Cervical Spine Anatomy-Axis

C2 The Axis has an unusual thumb-like extension of its vertebral body that passes through the arch of C1 This process is called the

dens or odontoid The odontoid process is normally held very tightly against the anterior arch of C1 by the transverse ligament

Meanwhile the spinal cord travels behind the odontoid within the

arch of C1

mohammad reza rajabi

Page 31 432012

Atlanto Axial Joint

This atlanto-axial joint provides the majority of the rotational motion of the cervical spine Meanwhile flexion and extension are primarily

accomplished at C2 and below and particularly between C4 and C6

Neck Movement with DL

What happens to the neck during direct laryngoscopy and

intubation

As you have seen the sniffing position involves neck flexion in the lower cervical spine with extension superiorly In the process of

direct laryngoscopy this motion is accentuated As the laryngoscope

is lifted upward the occiput is extended primarily at the atlanto-occipital joint (occiput-C1) while flexion occurs at C2-3 and below

Therefore any intervention that impedes this flexion and extension

will make visualization of the glottis more difficult In someone with a cervical fusion up to the occiput it is pretty much impossible to

perform direct laryngoscopy Similarly a patient with external stabilization such as a c-collar in this case will (SHOULD) have neck

movement reduced sufficient to make visualization difficult if not impossible

mohammad reza rajabi

Page 32 432012

Clearing the C-Spine

How does one rule out damage to the cervical spine

At present history is our greatest ally If the healthy patient has no history of neck problems and no symptoms on maximal flexion and

extension they are unlikely to have cervical spine disease

On the other hand there are many patients whose cervical spine

SHOULD be radiographically evaluated pre-operatively including certain trauma patients as well as those with disease states that

affect the cervical spine including rheumatoid arthritis and Downs Syndrome These diseases may affect the transverse ligament and

thus the stability at the atlanto-axial joint

Nexus Criteria

Which trauma patients require cervical spine films prior to surgery or

intubation There is a set of criteria identified by the National Emergency X-

Radiography Utilization Study (NEXUS) that attempt to identify patients with a low probability of injury thereby reducing the

number of negative cervical spine radiographs taken

The criteria include No midline cervical tenderness

No focal neurologic deficit

Normal alertness

No intoxication

No painful distracting injury that might make them ignore their

neck pain

For those patients whose cervical spine is not cleared the

anesthesiologist must consider the risks of cervical spine damage that can be worsened through direct laryngoscopy versus the risk of

alternative techniques that may minimize neck motion including awake fiberoptic intubation A description of these alternate

techniques is beyond the scope of this site at present

mohammad reza rajabi

Page 33 432012

Spine Film

For the current case the following film is obtained

Patients Film

Normal for Comparison

mohammad reza rajabi

Page 34 432012

Explanation

Note the large step-off between C6 and C7 This subluxation causes entrapment of the spinal cord and damage

Therefore this patient requires an intubation technique with minimal neck motion and awake positioningas well as some external

stabilization or operative intervention to prevent damage to the spinal cord at the neck

mohammad reza rajabi

Page 35 432012

C-Spine Review

So which patients are at higher risk for neck injury during intubation

Trauma patients

Yes No

(yes)Correct

They may have trauma to the cervical spine as well

(no)Incorrect

They may have trauma to the cervical spine as well

Rheumatoid arthritis patients

Yes No

(yes)Correct

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

(no)Incorrect

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

Downs Syndrome patients

Yes No

(yes)Correct

About 15 of these patients have laxity in the transverse ligament

that holds the odontoid against the anterior arch of C1 Xrays are also recommended in these patients prior to anticipated neck

manipulation including laryngoscopy

mohammad reza rajabi

Page 36 432012

(no)Incorrect

About 15 of these patients have laxity in the transverse ligament that holds the odontoid against the anterior arch of C1 Xrays are

also recommended in these patients prior to anticipated neck manipulation including laryngoscopy

Osteoarthritic patients

Yes No

(yes)Incorrect

They are not at higher risk

(no)Correct

They are not at higher risk

Patient with a prior cervical spine fusion

Yes No

(yes)Incorrect

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

(no)Correct

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

mohammad reza rajabi

Page 37 432012

Airway References

Cricoid Pressure

Vanner RG Asai T Safe use of cricoid pressure Anaesthesia 1999 54 1-3 A review of literature with recommendations

Sellick BA Cricoid pressure to control regurgitation of stomach contents during induction of anaesthesia Lancet 1961 2 404-6 The original description

Views and Grades

Mallampati SR Gatt SP et al A clinical sign to predict difficult tracheal intubation a prospective study Can Anaesth Soc J 198532(4)429-434 The original paper describing the classification system but only 3 grades (III and IV combined)

Samsoon GLT and Young JRB Difficult tracheal intubation a retrospective study Anaesthesia 198742487-490 Describes the addition of Mallampati class 4

Cormack RS and Lehane J Difficult tracheal intubation in obstetrics Anaesthesia 1984391105-1111 Describes the laryngoscopy grades and correlates with difficult intubation Also proposes a technique of attempting to intubate while intentionally achieving a suboptimal (Class III) view

Studies of Predictive Indices

There are many studies some which counter others One difficulty is defining a difficult airway Most use a Cormack-Lehane laryngoscopy grade of III-IV Some investigate specific radiographic measurements that are impractical in daily clinical practice Below are a few useful references

El-Ganzouri AR McCarthy RJ et al Preoperative airway assessment Predictive value of a multivariate risk index Anesth Analg 1996821197-1204 A logistic regression comparing examination tests and developing a risk index

Chou HC Wu TL et al Mandibulohyoid distance in difficult laryngoscopy Br J Anaesth 1993 71335-339 A single article sighting this distance as an important factor in an analysis of only 11 patients

Frerk CM Predicting difficult intubation Anaesthesia 1991461005-1008 A study suggesting that a Mallampati Class III or IV with thyromental distance of lt7cm is sensitive and specific for difficult intubation (laryngoscopy grade 3 or 4)

C-Spine Evaluation

mohammad reza rajabi

Page 38 432012

Hoffman JR Mower WR et al Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma N Engl J Med 200034394-99 Application of the NEXUS criteria

mohammad reza rajabi

Page 20 432012

Trachea below vocal cords - Recurrent Laryngeal Nerve

(Vagus X)

MOTOR INNERVATION

Motor innervation to the larynx is provided by the Vagus Nerve but recall there are two branches involved The Recurrent Laryngeal

Nerve innervates all the muscles of the larynx EXCEPT the

cricothyroid muscle which is innervated by the External Branch of the Superior Laryngeal Nerve Because the function of the

cricothyroid muscle is to stretch and tense the vocal cords unopposed action of the cricothyroid as may occur with bilateral

destruction of the recurrent laryngeal nerves would lead to stridor respiratory distress and possibly airway obstruction

GAG REFLEX

So the sensory afferent limb of the gag reflex is the glossopharyngeal nerve (IX) while the motor efferent limb is the

Vagus (X)

Its not much of a mnemonic but I remember this as a variant of TGIF Thank God its Recurrent I know its lame perhaps just

lame enough to be memorable

Airway Blocks

Topical application of local anesthetics is usually sufficient for the tongue and oronasopharynx though glossopharyngeal blocks are

performed occasionally Blunting of the gag reflex requires Transtracheal (really translaryngeal) with or without bilateral

Superior Laryngeal Nerve blocks as shown below

mohammad reza rajabi

Page 21 432012

The superior laryngeal nerves are blocked by deposition of 1 lidocaine near where the nerves penetrate the thyrohyoid

membrane The transtracheal block is accomplished with 4 lidocaine injected directly into the tracheal lumen Often this block

alone coupled with nebulized or atomized lidocaine is sufficient for awake intubation

mohammad reza rajabi

Page 22 432012

Airway Structures

The right panel displays images seen during fiberoptic bronchoscopy The corresponding level on CT is displayed on the middle panel

Place the cursor over structures to learn their identity

mohammad reza rajabi

Page 23 432012

mohammad reza rajabi

Page 24 432012

Review of Airway Innervation

Lets review the innervation of the upper airway

mohammad reza rajabi

Page 25 432012

Purple

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(V)Yes

The maxillary branch (V2) supplies the nasal cavity and palate while the mandibular branch (V3) supplies the anterior 23 of the tongue

(IX)Incorrect

The glossopharyngeal nerve supplies sensation to the posterior 13

of the tongue and its overlying structures including the soft palate

(X)No

The vagus innervates the airway further distal

Green

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)Yes

The glossopharyngeal nerve supplies sensation to the posterior 13

of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(X)No

The vagus innervates the airway further distal

mohammad reza rajabi

Page 26 432012

Blue

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)No

The glossopharyngeal nerve supplies sensation to the posterior 13 of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(x)Yes but which branch

Internal branch of superior laryngeal

External branch of superior laryngeal

Recurrent laryngeal

(Yes

The Internal Branch of the Superior Laryngeal Nerve provides

sensory innervation to the mucous membrane from the epiglottis to

and including the vocal cords

Incorrect

The External Branch of the Superior Laryngeal nerve provides motor innervation to the cricothyroid muscle only

Incorrect

The Recurrent Laryngeal Nerve supplies sensory innervation to the

trachea below the vocal cords as well as motor innervation to all the

intrinsic muscles of the larynx except the cricothyroid muscle)

mohammad reza rajabi

Page 27 432012

Red

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)No

The glossopharyngeal nerve supplies sensation to the posterior 13 of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(x)Yes but which branch

Internal branch of superior laryngeal

External branch of superior laryngeal

Recurrent laryngeal

(Incorrect

The Internal Branch of the Superior Laryngeal Nerve provides sensory innervation to the mucous membrane from the epiglottis to

and including the vocal cords

Incorrect

The External Branch of the Superior Laryngeal nerve provides motor innervation to the cricothyroid muscle only

Yes

The Recurrent Laryngeal Nerve supplies sensory innervation to the

trachea below the vocal cords as well as motor innervation to all the

intrinsic muscles of the larynx except the cricothyroid muscle)

mohammad reza rajabi

Page 28 432012

Case 3 Spine Evaluation

A previously healthy 40-year-old male presents with an open femur fracture from a Motor Vehicle Accident (MVA) that needs to be

repaired under general anesthesia He is currently on a backboard

with a cervical collar in place and is hemodynamically stable

Examination of this patients airway is complicated by the presence of the cervical collar which both inhibits mouth opening and by

definition prevents neck extension As you have seen above neck extension is required for direct laryngoscopy

So what shall we do

Remove the neck collar and intubate as usual

Intubate with a technique that does not require neck movement

Avoid general anesthesia and perform a regional block for the

procedure

Perform studies to clear the cervical spine

First a basic review of the anatomy is helpful

Recall that the cervical spine consists of 7 vertebrae the first two of

which are highly specialized

(Should this patient have an unstable cervical spine the movement resulting from laryngoscopy could permanently damage the spinal

cord likely resulting in quadriplegia)

(There are numerous techniques (retrograde intubationhellip) purported

to involve less cervical spine motion each of which requires substantial skill and experience These should only be attempted by

experienced practitioners Some advocate in-line stabilization where a second person attempts to hold the cervical spine still while

the primary person attempts direct laryngoscopy This technique makes intubation more difficult and is inadequate for stabilization)

mohammad reza rajabi

Page 29 432012

(While an attractive option many would argue that anytime a

regional anesthetic is planned immediate endotracheal intubation must be possible Complications may occur during the regional block

or it may be inadequate for the operation or wear off before the surgeons are done Therefore inability to emergently intubate a

patient is a relative contraindication to regional anesthesia and should be considered in this patient with a possible unstable neck)

(Great idea)

Cervical Spine Anatomy-Atlas

C1 The Atlas is a ring that interacts with the skull base above and

C2 shown on next page It is unique in that it lacks a vertebral body and spinous process The articulation of C1 with the occiput is very

tight providing little of the flexion of the cervical spine and only about 20 degrees of extension

mohammad reza rajabi

Page 30 432012

Cervical Spine Anatomy-Axis

C2 The Axis has an unusual thumb-like extension of its vertebral body that passes through the arch of C1 This process is called the

dens or odontoid The odontoid process is normally held very tightly against the anterior arch of C1 by the transverse ligament

Meanwhile the spinal cord travels behind the odontoid within the

arch of C1

mohammad reza rajabi

Page 31 432012

Atlanto Axial Joint

This atlanto-axial joint provides the majority of the rotational motion of the cervical spine Meanwhile flexion and extension are primarily

accomplished at C2 and below and particularly between C4 and C6

Neck Movement with DL

What happens to the neck during direct laryngoscopy and

intubation

As you have seen the sniffing position involves neck flexion in the lower cervical spine with extension superiorly In the process of

direct laryngoscopy this motion is accentuated As the laryngoscope

is lifted upward the occiput is extended primarily at the atlanto-occipital joint (occiput-C1) while flexion occurs at C2-3 and below

Therefore any intervention that impedes this flexion and extension

will make visualization of the glottis more difficult In someone with a cervical fusion up to the occiput it is pretty much impossible to

perform direct laryngoscopy Similarly a patient with external stabilization such as a c-collar in this case will (SHOULD) have neck

movement reduced sufficient to make visualization difficult if not impossible

mohammad reza rajabi

Page 32 432012

Clearing the C-Spine

How does one rule out damage to the cervical spine

At present history is our greatest ally If the healthy patient has no history of neck problems and no symptoms on maximal flexion and

extension they are unlikely to have cervical spine disease

On the other hand there are many patients whose cervical spine

SHOULD be radiographically evaluated pre-operatively including certain trauma patients as well as those with disease states that

affect the cervical spine including rheumatoid arthritis and Downs Syndrome These diseases may affect the transverse ligament and

thus the stability at the atlanto-axial joint

Nexus Criteria

Which trauma patients require cervical spine films prior to surgery or

intubation There is a set of criteria identified by the National Emergency X-

Radiography Utilization Study (NEXUS) that attempt to identify patients with a low probability of injury thereby reducing the

number of negative cervical spine radiographs taken

The criteria include No midline cervical tenderness

No focal neurologic deficit

Normal alertness

No intoxication

No painful distracting injury that might make them ignore their

neck pain

For those patients whose cervical spine is not cleared the

anesthesiologist must consider the risks of cervical spine damage that can be worsened through direct laryngoscopy versus the risk of

alternative techniques that may minimize neck motion including awake fiberoptic intubation A description of these alternate

techniques is beyond the scope of this site at present

mohammad reza rajabi

Page 33 432012

Spine Film

For the current case the following film is obtained

Patients Film

Normal for Comparison

mohammad reza rajabi

Page 34 432012

Explanation

Note the large step-off between C6 and C7 This subluxation causes entrapment of the spinal cord and damage

Therefore this patient requires an intubation technique with minimal neck motion and awake positioningas well as some external

stabilization or operative intervention to prevent damage to the spinal cord at the neck

mohammad reza rajabi

Page 35 432012

C-Spine Review

So which patients are at higher risk for neck injury during intubation

Trauma patients

Yes No

(yes)Correct

They may have trauma to the cervical spine as well

(no)Incorrect

They may have trauma to the cervical spine as well

Rheumatoid arthritis patients

Yes No

(yes)Correct

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

(no)Incorrect

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

Downs Syndrome patients

Yes No

(yes)Correct

About 15 of these patients have laxity in the transverse ligament

that holds the odontoid against the anterior arch of C1 Xrays are also recommended in these patients prior to anticipated neck

manipulation including laryngoscopy

mohammad reza rajabi

Page 36 432012

(no)Incorrect

About 15 of these patients have laxity in the transverse ligament that holds the odontoid against the anterior arch of C1 Xrays are

also recommended in these patients prior to anticipated neck manipulation including laryngoscopy

Osteoarthritic patients

Yes No

(yes)Incorrect

They are not at higher risk

(no)Correct

They are not at higher risk

Patient with a prior cervical spine fusion

Yes No

(yes)Incorrect

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

(no)Correct

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

mohammad reza rajabi

Page 37 432012

Airway References

Cricoid Pressure

Vanner RG Asai T Safe use of cricoid pressure Anaesthesia 1999 54 1-3 A review of literature with recommendations

Sellick BA Cricoid pressure to control regurgitation of stomach contents during induction of anaesthesia Lancet 1961 2 404-6 The original description

Views and Grades

Mallampati SR Gatt SP et al A clinical sign to predict difficult tracheal intubation a prospective study Can Anaesth Soc J 198532(4)429-434 The original paper describing the classification system but only 3 grades (III and IV combined)

Samsoon GLT and Young JRB Difficult tracheal intubation a retrospective study Anaesthesia 198742487-490 Describes the addition of Mallampati class 4

Cormack RS and Lehane J Difficult tracheal intubation in obstetrics Anaesthesia 1984391105-1111 Describes the laryngoscopy grades and correlates with difficult intubation Also proposes a technique of attempting to intubate while intentionally achieving a suboptimal (Class III) view

Studies of Predictive Indices

There are many studies some which counter others One difficulty is defining a difficult airway Most use a Cormack-Lehane laryngoscopy grade of III-IV Some investigate specific radiographic measurements that are impractical in daily clinical practice Below are a few useful references

El-Ganzouri AR McCarthy RJ et al Preoperative airway assessment Predictive value of a multivariate risk index Anesth Analg 1996821197-1204 A logistic regression comparing examination tests and developing a risk index

Chou HC Wu TL et al Mandibulohyoid distance in difficult laryngoscopy Br J Anaesth 1993 71335-339 A single article sighting this distance as an important factor in an analysis of only 11 patients

Frerk CM Predicting difficult intubation Anaesthesia 1991461005-1008 A study suggesting that a Mallampati Class III or IV with thyromental distance of lt7cm is sensitive and specific for difficult intubation (laryngoscopy grade 3 or 4)

C-Spine Evaluation

mohammad reza rajabi

Page 38 432012

Hoffman JR Mower WR et al Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma N Engl J Med 200034394-99 Application of the NEXUS criteria

mohammad reza rajabi

Page 21 432012

The superior laryngeal nerves are blocked by deposition of 1 lidocaine near where the nerves penetrate the thyrohyoid

membrane The transtracheal block is accomplished with 4 lidocaine injected directly into the tracheal lumen Often this block

alone coupled with nebulized or atomized lidocaine is sufficient for awake intubation

mohammad reza rajabi

Page 22 432012

Airway Structures

The right panel displays images seen during fiberoptic bronchoscopy The corresponding level on CT is displayed on the middle panel

Place the cursor over structures to learn their identity

mohammad reza rajabi

Page 23 432012

mohammad reza rajabi

Page 24 432012

Review of Airway Innervation

Lets review the innervation of the upper airway

mohammad reza rajabi

Page 25 432012

Purple

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(V)Yes

The maxillary branch (V2) supplies the nasal cavity and palate while the mandibular branch (V3) supplies the anterior 23 of the tongue

(IX)Incorrect

The glossopharyngeal nerve supplies sensation to the posterior 13

of the tongue and its overlying structures including the soft palate

(X)No

The vagus innervates the airway further distal

Green

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)Yes

The glossopharyngeal nerve supplies sensation to the posterior 13

of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(X)No

The vagus innervates the airway further distal

mohammad reza rajabi

Page 26 432012

Blue

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)No

The glossopharyngeal nerve supplies sensation to the posterior 13 of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(x)Yes but which branch

Internal branch of superior laryngeal

External branch of superior laryngeal

Recurrent laryngeal

(Yes

The Internal Branch of the Superior Laryngeal Nerve provides

sensory innervation to the mucous membrane from the epiglottis to

and including the vocal cords

Incorrect

The External Branch of the Superior Laryngeal nerve provides motor innervation to the cricothyroid muscle only

Incorrect

The Recurrent Laryngeal Nerve supplies sensory innervation to the

trachea below the vocal cords as well as motor innervation to all the

intrinsic muscles of the larynx except the cricothyroid muscle)

mohammad reza rajabi

Page 27 432012

Red

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)No

The glossopharyngeal nerve supplies sensation to the posterior 13 of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(x)Yes but which branch

Internal branch of superior laryngeal

External branch of superior laryngeal

Recurrent laryngeal

(Incorrect

The Internal Branch of the Superior Laryngeal Nerve provides sensory innervation to the mucous membrane from the epiglottis to

and including the vocal cords

Incorrect

The External Branch of the Superior Laryngeal nerve provides motor innervation to the cricothyroid muscle only

Yes

The Recurrent Laryngeal Nerve supplies sensory innervation to the

trachea below the vocal cords as well as motor innervation to all the

intrinsic muscles of the larynx except the cricothyroid muscle)

mohammad reza rajabi

Page 28 432012

Case 3 Spine Evaluation

A previously healthy 40-year-old male presents with an open femur fracture from a Motor Vehicle Accident (MVA) that needs to be

repaired under general anesthesia He is currently on a backboard

with a cervical collar in place and is hemodynamically stable

Examination of this patients airway is complicated by the presence of the cervical collar which both inhibits mouth opening and by

definition prevents neck extension As you have seen above neck extension is required for direct laryngoscopy

So what shall we do

Remove the neck collar and intubate as usual

Intubate with a technique that does not require neck movement

Avoid general anesthesia and perform a regional block for the

procedure

Perform studies to clear the cervical spine

First a basic review of the anatomy is helpful

Recall that the cervical spine consists of 7 vertebrae the first two of

which are highly specialized

(Should this patient have an unstable cervical spine the movement resulting from laryngoscopy could permanently damage the spinal

cord likely resulting in quadriplegia)

(There are numerous techniques (retrograde intubationhellip) purported

to involve less cervical spine motion each of which requires substantial skill and experience These should only be attempted by

experienced practitioners Some advocate in-line stabilization where a second person attempts to hold the cervical spine still while

the primary person attempts direct laryngoscopy This technique makes intubation more difficult and is inadequate for stabilization)

mohammad reza rajabi

Page 29 432012

(While an attractive option many would argue that anytime a

regional anesthetic is planned immediate endotracheal intubation must be possible Complications may occur during the regional block

or it may be inadequate for the operation or wear off before the surgeons are done Therefore inability to emergently intubate a

patient is a relative contraindication to regional anesthesia and should be considered in this patient with a possible unstable neck)

(Great idea)

Cervical Spine Anatomy-Atlas

C1 The Atlas is a ring that interacts with the skull base above and

C2 shown on next page It is unique in that it lacks a vertebral body and spinous process The articulation of C1 with the occiput is very

tight providing little of the flexion of the cervical spine and only about 20 degrees of extension

mohammad reza rajabi

Page 30 432012

Cervical Spine Anatomy-Axis

C2 The Axis has an unusual thumb-like extension of its vertebral body that passes through the arch of C1 This process is called the

dens or odontoid The odontoid process is normally held very tightly against the anterior arch of C1 by the transverse ligament

Meanwhile the spinal cord travels behind the odontoid within the

arch of C1

mohammad reza rajabi

Page 31 432012

Atlanto Axial Joint

This atlanto-axial joint provides the majority of the rotational motion of the cervical spine Meanwhile flexion and extension are primarily

accomplished at C2 and below and particularly between C4 and C6

Neck Movement with DL

What happens to the neck during direct laryngoscopy and

intubation

As you have seen the sniffing position involves neck flexion in the lower cervical spine with extension superiorly In the process of

direct laryngoscopy this motion is accentuated As the laryngoscope

is lifted upward the occiput is extended primarily at the atlanto-occipital joint (occiput-C1) while flexion occurs at C2-3 and below

Therefore any intervention that impedes this flexion and extension

will make visualization of the glottis more difficult In someone with a cervical fusion up to the occiput it is pretty much impossible to

perform direct laryngoscopy Similarly a patient with external stabilization such as a c-collar in this case will (SHOULD) have neck

movement reduced sufficient to make visualization difficult if not impossible

mohammad reza rajabi

Page 32 432012

Clearing the C-Spine

How does one rule out damage to the cervical spine

At present history is our greatest ally If the healthy patient has no history of neck problems and no symptoms on maximal flexion and

extension they are unlikely to have cervical spine disease

On the other hand there are many patients whose cervical spine

SHOULD be radiographically evaluated pre-operatively including certain trauma patients as well as those with disease states that

affect the cervical spine including rheumatoid arthritis and Downs Syndrome These diseases may affect the transverse ligament and

thus the stability at the atlanto-axial joint

Nexus Criteria

Which trauma patients require cervical spine films prior to surgery or

intubation There is a set of criteria identified by the National Emergency X-

Radiography Utilization Study (NEXUS) that attempt to identify patients with a low probability of injury thereby reducing the

number of negative cervical spine radiographs taken

The criteria include No midline cervical tenderness

No focal neurologic deficit

Normal alertness

No intoxication

No painful distracting injury that might make them ignore their

neck pain

For those patients whose cervical spine is not cleared the

anesthesiologist must consider the risks of cervical spine damage that can be worsened through direct laryngoscopy versus the risk of

alternative techniques that may minimize neck motion including awake fiberoptic intubation A description of these alternate

techniques is beyond the scope of this site at present

mohammad reza rajabi

Page 33 432012

Spine Film

For the current case the following film is obtained

Patients Film

Normal for Comparison

mohammad reza rajabi

Page 34 432012

Explanation

Note the large step-off between C6 and C7 This subluxation causes entrapment of the spinal cord and damage

Therefore this patient requires an intubation technique with minimal neck motion and awake positioningas well as some external

stabilization or operative intervention to prevent damage to the spinal cord at the neck

mohammad reza rajabi

Page 35 432012

C-Spine Review

So which patients are at higher risk for neck injury during intubation

Trauma patients

Yes No

(yes)Correct

They may have trauma to the cervical spine as well

(no)Incorrect

They may have trauma to the cervical spine as well

Rheumatoid arthritis patients

Yes No

(yes)Correct

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

(no)Incorrect

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

Downs Syndrome patients

Yes No

(yes)Correct

About 15 of these patients have laxity in the transverse ligament

that holds the odontoid against the anterior arch of C1 Xrays are also recommended in these patients prior to anticipated neck

manipulation including laryngoscopy

mohammad reza rajabi

Page 36 432012

(no)Incorrect

About 15 of these patients have laxity in the transverse ligament that holds the odontoid against the anterior arch of C1 Xrays are

also recommended in these patients prior to anticipated neck manipulation including laryngoscopy

Osteoarthritic patients

Yes No

(yes)Incorrect

They are not at higher risk

(no)Correct

They are not at higher risk

Patient with a prior cervical spine fusion

Yes No

(yes)Incorrect

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

(no)Correct

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

mohammad reza rajabi

Page 37 432012

Airway References

Cricoid Pressure

Vanner RG Asai T Safe use of cricoid pressure Anaesthesia 1999 54 1-3 A review of literature with recommendations

Sellick BA Cricoid pressure to control regurgitation of stomach contents during induction of anaesthesia Lancet 1961 2 404-6 The original description

Views and Grades

Mallampati SR Gatt SP et al A clinical sign to predict difficult tracheal intubation a prospective study Can Anaesth Soc J 198532(4)429-434 The original paper describing the classification system but only 3 grades (III and IV combined)

Samsoon GLT and Young JRB Difficult tracheal intubation a retrospective study Anaesthesia 198742487-490 Describes the addition of Mallampati class 4

Cormack RS and Lehane J Difficult tracheal intubation in obstetrics Anaesthesia 1984391105-1111 Describes the laryngoscopy grades and correlates with difficult intubation Also proposes a technique of attempting to intubate while intentionally achieving a suboptimal (Class III) view

Studies of Predictive Indices

There are many studies some which counter others One difficulty is defining a difficult airway Most use a Cormack-Lehane laryngoscopy grade of III-IV Some investigate specific radiographic measurements that are impractical in daily clinical practice Below are a few useful references

El-Ganzouri AR McCarthy RJ et al Preoperative airway assessment Predictive value of a multivariate risk index Anesth Analg 1996821197-1204 A logistic regression comparing examination tests and developing a risk index

Chou HC Wu TL et al Mandibulohyoid distance in difficult laryngoscopy Br J Anaesth 1993 71335-339 A single article sighting this distance as an important factor in an analysis of only 11 patients

Frerk CM Predicting difficult intubation Anaesthesia 1991461005-1008 A study suggesting that a Mallampati Class III or IV with thyromental distance of lt7cm is sensitive and specific for difficult intubation (laryngoscopy grade 3 or 4)

C-Spine Evaluation

mohammad reza rajabi

Page 38 432012

Hoffman JR Mower WR et al Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma N Engl J Med 200034394-99 Application of the NEXUS criteria

mohammad reza rajabi

Page 22 432012

Airway Structures

The right panel displays images seen during fiberoptic bronchoscopy The corresponding level on CT is displayed on the middle panel

Place the cursor over structures to learn their identity

mohammad reza rajabi

Page 23 432012

mohammad reza rajabi

Page 24 432012

Review of Airway Innervation

Lets review the innervation of the upper airway

mohammad reza rajabi

Page 25 432012

Purple

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(V)Yes

The maxillary branch (V2) supplies the nasal cavity and palate while the mandibular branch (V3) supplies the anterior 23 of the tongue

(IX)Incorrect

The glossopharyngeal nerve supplies sensation to the posterior 13

of the tongue and its overlying structures including the soft palate

(X)No

The vagus innervates the airway further distal

Green

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)Yes

The glossopharyngeal nerve supplies sensation to the posterior 13

of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(X)No

The vagus innervates the airway further distal

mohammad reza rajabi

Page 26 432012

Blue

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)No

The glossopharyngeal nerve supplies sensation to the posterior 13 of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(x)Yes but which branch

Internal branch of superior laryngeal

External branch of superior laryngeal

Recurrent laryngeal

(Yes

The Internal Branch of the Superior Laryngeal Nerve provides

sensory innervation to the mucous membrane from the epiglottis to

and including the vocal cords

Incorrect

The External Branch of the Superior Laryngeal nerve provides motor innervation to the cricothyroid muscle only

Incorrect

The Recurrent Laryngeal Nerve supplies sensory innervation to the

trachea below the vocal cords as well as motor innervation to all the

intrinsic muscles of the larynx except the cricothyroid muscle)

mohammad reza rajabi

Page 27 432012

Red

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)No

The glossopharyngeal nerve supplies sensation to the posterior 13 of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(x)Yes but which branch

Internal branch of superior laryngeal

External branch of superior laryngeal

Recurrent laryngeal

(Incorrect

The Internal Branch of the Superior Laryngeal Nerve provides sensory innervation to the mucous membrane from the epiglottis to

and including the vocal cords

Incorrect

The External Branch of the Superior Laryngeal nerve provides motor innervation to the cricothyroid muscle only

Yes

The Recurrent Laryngeal Nerve supplies sensory innervation to the

trachea below the vocal cords as well as motor innervation to all the

intrinsic muscles of the larynx except the cricothyroid muscle)

mohammad reza rajabi

Page 28 432012

Case 3 Spine Evaluation

A previously healthy 40-year-old male presents with an open femur fracture from a Motor Vehicle Accident (MVA) that needs to be

repaired under general anesthesia He is currently on a backboard

with a cervical collar in place and is hemodynamically stable

Examination of this patients airway is complicated by the presence of the cervical collar which both inhibits mouth opening and by

definition prevents neck extension As you have seen above neck extension is required for direct laryngoscopy

So what shall we do

Remove the neck collar and intubate as usual

Intubate with a technique that does not require neck movement

Avoid general anesthesia and perform a regional block for the

procedure

Perform studies to clear the cervical spine

First a basic review of the anatomy is helpful

Recall that the cervical spine consists of 7 vertebrae the first two of

which are highly specialized

(Should this patient have an unstable cervical spine the movement resulting from laryngoscopy could permanently damage the spinal

cord likely resulting in quadriplegia)

(There are numerous techniques (retrograde intubationhellip) purported

to involve less cervical spine motion each of which requires substantial skill and experience These should only be attempted by

experienced practitioners Some advocate in-line stabilization where a second person attempts to hold the cervical spine still while

the primary person attempts direct laryngoscopy This technique makes intubation more difficult and is inadequate for stabilization)

mohammad reza rajabi

Page 29 432012

(While an attractive option many would argue that anytime a

regional anesthetic is planned immediate endotracheal intubation must be possible Complications may occur during the regional block

or it may be inadequate for the operation or wear off before the surgeons are done Therefore inability to emergently intubate a

patient is a relative contraindication to regional anesthesia and should be considered in this patient with a possible unstable neck)

(Great idea)

Cervical Spine Anatomy-Atlas

C1 The Atlas is a ring that interacts with the skull base above and

C2 shown on next page It is unique in that it lacks a vertebral body and spinous process The articulation of C1 with the occiput is very

tight providing little of the flexion of the cervical spine and only about 20 degrees of extension

mohammad reza rajabi

Page 30 432012

Cervical Spine Anatomy-Axis

C2 The Axis has an unusual thumb-like extension of its vertebral body that passes through the arch of C1 This process is called the

dens or odontoid The odontoid process is normally held very tightly against the anterior arch of C1 by the transverse ligament

Meanwhile the spinal cord travels behind the odontoid within the

arch of C1

mohammad reza rajabi

Page 31 432012

Atlanto Axial Joint

This atlanto-axial joint provides the majority of the rotational motion of the cervical spine Meanwhile flexion and extension are primarily

accomplished at C2 and below and particularly between C4 and C6

Neck Movement with DL

What happens to the neck during direct laryngoscopy and

intubation

As you have seen the sniffing position involves neck flexion in the lower cervical spine with extension superiorly In the process of

direct laryngoscopy this motion is accentuated As the laryngoscope

is lifted upward the occiput is extended primarily at the atlanto-occipital joint (occiput-C1) while flexion occurs at C2-3 and below

Therefore any intervention that impedes this flexion and extension

will make visualization of the glottis more difficult In someone with a cervical fusion up to the occiput it is pretty much impossible to

perform direct laryngoscopy Similarly a patient with external stabilization such as a c-collar in this case will (SHOULD) have neck

movement reduced sufficient to make visualization difficult if not impossible

mohammad reza rajabi

Page 32 432012

Clearing the C-Spine

How does one rule out damage to the cervical spine

At present history is our greatest ally If the healthy patient has no history of neck problems and no symptoms on maximal flexion and

extension they are unlikely to have cervical spine disease

On the other hand there are many patients whose cervical spine

SHOULD be radiographically evaluated pre-operatively including certain trauma patients as well as those with disease states that

affect the cervical spine including rheumatoid arthritis and Downs Syndrome These diseases may affect the transverse ligament and

thus the stability at the atlanto-axial joint

Nexus Criteria

Which trauma patients require cervical spine films prior to surgery or

intubation There is a set of criteria identified by the National Emergency X-

Radiography Utilization Study (NEXUS) that attempt to identify patients with a low probability of injury thereby reducing the

number of negative cervical spine radiographs taken

The criteria include No midline cervical tenderness

No focal neurologic deficit

Normal alertness

No intoxication

No painful distracting injury that might make them ignore their

neck pain

For those patients whose cervical spine is not cleared the

anesthesiologist must consider the risks of cervical spine damage that can be worsened through direct laryngoscopy versus the risk of

alternative techniques that may minimize neck motion including awake fiberoptic intubation A description of these alternate

techniques is beyond the scope of this site at present

mohammad reza rajabi

Page 33 432012

Spine Film

For the current case the following film is obtained

Patients Film

Normal for Comparison

mohammad reza rajabi

Page 34 432012

Explanation

Note the large step-off between C6 and C7 This subluxation causes entrapment of the spinal cord and damage

Therefore this patient requires an intubation technique with minimal neck motion and awake positioningas well as some external

stabilization or operative intervention to prevent damage to the spinal cord at the neck

mohammad reza rajabi

Page 35 432012

C-Spine Review

So which patients are at higher risk for neck injury during intubation

Trauma patients

Yes No

(yes)Correct

They may have trauma to the cervical spine as well

(no)Incorrect

They may have trauma to the cervical spine as well

Rheumatoid arthritis patients

Yes No

(yes)Correct

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

(no)Incorrect

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

Downs Syndrome patients

Yes No

(yes)Correct

About 15 of these patients have laxity in the transverse ligament

that holds the odontoid against the anterior arch of C1 Xrays are also recommended in these patients prior to anticipated neck

manipulation including laryngoscopy

mohammad reza rajabi

Page 36 432012

(no)Incorrect

About 15 of these patients have laxity in the transverse ligament that holds the odontoid against the anterior arch of C1 Xrays are

also recommended in these patients prior to anticipated neck manipulation including laryngoscopy

Osteoarthritic patients

Yes No

(yes)Incorrect

They are not at higher risk

(no)Correct

They are not at higher risk

Patient with a prior cervical spine fusion

Yes No

(yes)Incorrect

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

(no)Correct

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

mohammad reza rajabi

Page 37 432012

Airway References

Cricoid Pressure

Vanner RG Asai T Safe use of cricoid pressure Anaesthesia 1999 54 1-3 A review of literature with recommendations

Sellick BA Cricoid pressure to control regurgitation of stomach contents during induction of anaesthesia Lancet 1961 2 404-6 The original description

Views and Grades

Mallampati SR Gatt SP et al A clinical sign to predict difficult tracheal intubation a prospective study Can Anaesth Soc J 198532(4)429-434 The original paper describing the classification system but only 3 grades (III and IV combined)

Samsoon GLT and Young JRB Difficult tracheal intubation a retrospective study Anaesthesia 198742487-490 Describes the addition of Mallampati class 4

Cormack RS and Lehane J Difficult tracheal intubation in obstetrics Anaesthesia 1984391105-1111 Describes the laryngoscopy grades and correlates with difficult intubation Also proposes a technique of attempting to intubate while intentionally achieving a suboptimal (Class III) view

Studies of Predictive Indices

There are many studies some which counter others One difficulty is defining a difficult airway Most use a Cormack-Lehane laryngoscopy grade of III-IV Some investigate specific radiographic measurements that are impractical in daily clinical practice Below are a few useful references

El-Ganzouri AR McCarthy RJ et al Preoperative airway assessment Predictive value of a multivariate risk index Anesth Analg 1996821197-1204 A logistic regression comparing examination tests and developing a risk index

Chou HC Wu TL et al Mandibulohyoid distance in difficult laryngoscopy Br J Anaesth 1993 71335-339 A single article sighting this distance as an important factor in an analysis of only 11 patients

Frerk CM Predicting difficult intubation Anaesthesia 1991461005-1008 A study suggesting that a Mallampati Class III or IV with thyromental distance of lt7cm is sensitive and specific for difficult intubation (laryngoscopy grade 3 or 4)

C-Spine Evaluation

mohammad reza rajabi

Page 38 432012

Hoffman JR Mower WR et al Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma N Engl J Med 200034394-99 Application of the NEXUS criteria

mohammad reza rajabi

Page 23 432012

mohammad reza rajabi

Page 24 432012

Review of Airway Innervation

Lets review the innervation of the upper airway

mohammad reza rajabi

Page 25 432012

Purple

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(V)Yes

The maxillary branch (V2) supplies the nasal cavity and palate while the mandibular branch (V3) supplies the anterior 23 of the tongue

(IX)Incorrect

The glossopharyngeal nerve supplies sensation to the posterior 13

of the tongue and its overlying structures including the soft palate

(X)No

The vagus innervates the airway further distal

Green

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)Yes

The glossopharyngeal nerve supplies sensation to the posterior 13

of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(X)No

The vagus innervates the airway further distal

mohammad reza rajabi

Page 26 432012

Blue

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)No

The glossopharyngeal nerve supplies sensation to the posterior 13 of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(x)Yes but which branch

Internal branch of superior laryngeal

External branch of superior laryngeal

Recurrent laryngeal

(Yes

The Internal Branch of the Superior Laryngeal Nerve provides

sensory innervation to the mucous membrane from the epiglottis to

and including the vocal cords

Incorrect

The External Branch of the Superior Laryngeal nerve provides motor innervation to the cricothyroid muscle only

Incorrect

The Recurrent Laryngeal Nerve supplies sensory innervation to the

trachea below the vocal cords as well as motor innervation to all the

intrinsic muscles of the larynx except the cricothyroid muscle)

mohammad reza rajabi

Page 27 432012

Red

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)No

The glossopharyngeal nerve supplies sensation to the posterior 13 of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(x)Yes but which branch

Internal branch of superior laryngeal

External branch of superior laryngeal

Recurrent laryngeal

(Incorrect

The Internal Branch of the Superior Laryngeal Nerve provides sensory innervation to the mucous membrane from the epiglottis to

and including the vocal cords

Incorrect

The External Branch of the Superior Laryngeal nerve provides motor innervation to the cricothyroid muscle only

Yes

The Recurrent Laryngeal Nerve supplies sensory innervation to the

trachea below the vocal cords as well as motor innervation to all the

intrinsic muscles of the larynx except the cricothyroid muscle)

mohammad reza rajabi

Page 28 432012

Case 3 Spine Evaluation

A previously healthy 40-year-old male presents with an open femur fracture from a Motor Vehicle Accident (MVA) that needs to be

repaired under general anesthesia He is currently on a backboard

with a cervical collar in place and is hemodynamically stable

Examination of this patients airway is complicated by the presence of the cervical collar which both inhibits mouth opening and by

definition prevents neck extension As you have seen above neck extension is required for direct laryngoscopy

So what shall we do

Remove the neck collar and intubate as usual

Intubate with a technique that does not require neck movement

Avoid general anesthesia and perform a regional block for the

procedure

Perform studies to clear the cervical spine

First a basic review of the anatomy is helpful

Recall that the cervical spine consists of 7 vertebrae the first two of

which are highly specialized

(Should this patient have an unstable cervical spine the movement resulting from laryngoscopy could permanently damage the spinal

cord likely resulting in quadriplegia)

(There are numerous techniques (retrograde intubationhellip) purported

to involve less cervical spine motion each of which requires substantial skill and experience These should only be attempted by

experienced practitioners Some advocate in-line stabilization where a second person attempts to hold the cervical spine still while

the primary person attempts direct laryngoscopy This technique makes intubation more difficult and is inadequate for stabilization)

mohammad reza rajabi

Page 29 432012

(While an attractive option many would argue that anytime a

regional anesthetic is planned immediate endotracheal intubation must be possible Complications may occur during the regional block

or it may be inadequate for the operation or wear off before the surgeons are done Therefore inability to emergently intubate a

patient is a relative contraindication to regional anesthesia and should be considered in this patient with a possible unstable neck)

(Great idea)

Cervical Spine Anatomy-Atlas

C1 The Atlas is a ring that interacts with the skull base above and

C2 shown on next page It is unique in that it lacks a vertebral body and spinous process The articulation of C1 with the occiput is very

tight providing little of the flexion of the cervical spine and only about 20 degrees of extension

mohammad reza rajabi

Page 30 432012

Cervical Spine Anatomy-Axis

C2 The Axis has an unusual thumb-like extension of its vertebral body that passes through the arch of C1 This process is called the

dens or odontoid The odontoid process is normally held very tightly against the anterior arch of C1 by the transverse ligament

Meanwhile the spinal cord travels behind the odontoid within the

arch of C1

mohammad reza rajabi

Page 31 432012

Atlanto Axial Joint

This atlanto-axial joint provides the majority of the rotational motion of the cervical spine Meanwhile flexion and extension are primarily

accomplished at C2 and below and particularly between C4 and C6

Neck Movement with DL

What happens to the neck during direct laryngoscopy and

intubation

As you have seen the sniffing position involves neck flexion in the lower cervical spine with extension superiorly In the process of

direct laryngoscopy this motion is accentuated As the laryngoscope

is lifted upward the occiput is extended primarily at the atlanto-occipital joint (occiput-C1) while flexion occurs at C2-3 and below

Therefore any intervention that impedes this flexion and extension

will make visualization of the glottis more difficult In someone with a cervical fusion up to the occiput it is pretty much impossible to

perform direct laryngoscopy Similarly a patient with external stabilization such as a c-collar in this case will (SHOULD) have neck

movement reduced sufficient to make visualization difficult if not impossible

mohammad reza rajabi

Page 32 432012

Clearing the C-Spine

How does one rule out damage to the cervical spine

At present history is our greatest ally If the healthy patient has no history of neck problems and no symptoms on maximal flexion and

extension they are unlikely to have cervical spine disease

On the other hand there are many patients whose cervical spine

SHOULD be radiographically evaluated pre-operatively including certain trauma patients as well as those with disease states that

affect the cervical spine including rheumatoid arthritis and Downs Syndrome These diseases may affect the transverse ligament and

thus the stability at the atlanto-axial joint

Nexus Criteria

Which trauma patients require cervical spine films prior to surgery or

intubation There is a set of criteria identified by the National Emergency X-

Radiography Utilization Study (NEXUS) that attempt to identify patients with a low probability of injury thereby reducing the

number of negative cervical spine radiographs taken

The criteria include No midline cervical tenderness

No focal neurologic deficit

Normal alertness

No intoxication

No painful distracting injury that might make them ignore their

neck pain

For those patients whose cervical spine is not cleared the

anesthesiologist must consider the risks of cervical spine damage that can be worsened through direct laryngoscopy versus the risk of

alternative techniques that may minimize neck motion including awake fiberoptic intubation A description of these alternate

techniques is beyond the scope of this site at present

mohammad reza rajabi

Page 33 432012

Spine Film

For the current case the following film is obtained

Patients Film

Normal for Comparison

mohammad reza rajabi

Page 34 432012

Explanation

Note the large step-off between C6 and C7 This subluxation causes entrapment of the spinal cord and damage

Therefore this patient requires an intubation technique with minimal neck motion and awake positioningas well as some external

stabilization or operative intervention to prevent damage to the spinal cord at the neck

mohammad reza rajabi

Page 35 432012

C-Spine Review

So which patients are at higher risk for neck injury during intubation

Trauma patients

Yes No

(yes)Correct

They may have trauma to the cervical spine as well

(no)Incorrect

They may have trauma to the cervical spine as well

Rheumatoid arthritis patients

Yes No

(yes)Correct

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

(no)Incorrect

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

Downs Syndrome patients

Yes No

(yes)Correct

About 15 of these patients have laxity in the transverse ligament

that holds the odontoid against the anterior arch of C1 Xrays are also recommended in these patients prior to anticipated neck

manipulation including laryngoscopy

mohammad reza rajabi

Page 36 432012

(no)Incorrect

About 15 of these patients have laxity in the transverse ligament that holds the odontoid against the anterior arch of C1 Xrays are

also recommended in these patients prior to anticipated neck manipulation including laryngoscopy

Osteoarthritic patients

Yes No

(yes)Incorrect

They are not at higher risk

(no)Correct

They are not at higher risk

Patient with a prior cervical spine fusion

Yes No

(yes)Incorrect

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

(no)Correct

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

mohammad reza rajabi

Page 37 432012

Airway References

Cricoid Pressure

Vanner RG Asai T Safe use of cricoid pressure Anaesthesia 1999 54 1-3 A review of literature with recommendations

Sellick BA Cricoid pressure to control regurgitation of stomach contents during induction of anaesthesia Lancet 1961 2 404-6 The original description

Views and Grades

Mallampati SR Gatt SP et al A clinical sign to predict difficult tracheal intubation a prospective study Can Anaesth Soc J 198532(4)429-434 The original paper describing the classification system but only 3 grades (III and IV combined)

Samsoon GLT and Young JRB Difficult tracheal intubation a retrospective study Anaesthesia 198742487-490 Describes the addition of Mallampati class 4

Cormack RS and Lehane J Difficult tracheal intubation in obstetrics Anaesthesia 1984391105-1111 Describes the laryngoscopy grades and correlates with difficult intubation Also proposes a technique of attempting to intubate while intentionally achieving a suboptimal (Class III) view

Studies of Predictive Indices

There are many studies some which counter others One difficulty is defining a difficult airway Most use a Cormack-Lehane laryngoscopy grade of III-IV Some investigate specific radiographic measurements that are impractical in daily clinical practice Below are a few useful references

El-Ganzouri AR McCarthy RJ et al Preoperative airway assessment Predictive value of a multivariate risk index Anesth Analg 1996821197-1204 A logistic regression comparing examination tests and developing a risk index

Chou HC Wu TL et al Mandibulohyoid distance in difficult laryngoscopy Br J Anaesth 1993 71335-339 A single article sighting this distance as an important factor in an analysis of only 11 patients

Frerk CM Predicting difficult intubation Anaesthesia 1991461005-1008 A study suggesting that a Mallampati Class III or IV with thyromental distance of lt7cm is sensitive and specific for difficult intubation (laryngoscopy grade 3 or 4)

C-Spine Evaluation

mohammad reza rajabi

Page 38 432012

Hoffman JR Mower WR et al Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma N Engl J Med 200034394-99 Application of the NEXUS criteria

mohammad reza rajabi

Page 24 432012

Review of Airway Innervation

Lets review the innervation of the upper airway

mohammad reza rajabi

Page 25 432012

Purple

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(V)Yes

The maxillary branch (V2) supplies the nasal cavity and palate while the mandibular branch (V3) supplies the anterior 23 of the tongue

(IX)Incorrect

The glossopharyngeal nerve supplies sensation to the posterior 13

of the tongue and its overlying structures including the soft palate

(X)No

The vagus innervates the airway further distal

Green

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)Yes

The glossopharyngeal nerve supplies sensation to the posterior 13

of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(X)No

The vagus innervates the airway further distal

mohammad reza rajabi

Page 26 432012

Blue

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)No

The glossopharyngeal nerve supplies sensation to the posterior 13 of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(x)Yes but which branch

Internal branch of superior laryngeal

External branch of superior laryngeal

Recurrent laryngeal

(Yes

The Internal Branch of the Superior Laryngeal Nerve provides

sensory innervation to the mucous membrane from the epiglottis to

and including the vocal cords

Incorrect

The External Branch of the Superior Laryngeal nerve provides motor innervation to the cricothyroid muscle only

Incorrect

The Recurrent Laryngeal Nerve supplies sensory innervation to the

trachea below the vocal cords as well as motor innervation to all the

intrinsic muscles of the larynx except the cricothyroid muscle)

mohammad reza rajabi

Page 27 432012

Red

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)No

The glossopharyngeal nerve supplies sensation to the posterior 13 of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(x)Yes but which branch

Internal branch of superior laryngeal

External branch of superior laryngeal

Recurrent laryngeal

(Incorrect

The Internal Branch of the Superior Laryngeal Nerve provides sensory innervation to the mucous membrane from the epiglottis to

and including the vocal cords

Incorrect

The External Branch of the Superior Laryngeal nerve provides motor innervation to the cricothyroid muscle only

Yes

The Recurrent Laryngeal Nerve supplies sensory innervation to the

trachea below the vocal cords as well as motor innervation to all the

intrinsic muscles of the larynx except the cricothyroid muscle)

mohammad reza rajabi

Page 28 432012

Case 3 Spine Evaluation

A previously healthy 40-year-old male presents with an open femur fracture from a Motor Vehicle Accident (MVA) that needs to be

repaired under general anesthesia He is currently on a backboard

with a cervical collar in place and is hemodynamically stable

Examination of this patients airway is complicated by the presence of the cervical collar which both inhibits mouth opening and by

definition prevents neck extension As you have seen above neck extension is required for direct laryngoscopy

So what shall we do

Remove the neck collar and intubate as usual

Intubate with a technique that does not require neck movement

Avoid general anesthesia and perform a regional block for the

procedure

Perform studies to clear the cervical spine

First a basic review of the anatomy is helpful

Recall that the cervical spine consists of 7 vertebrae the first two of

which are highly specialized

(Should this patient have an unstable cervical spine the movement resulting from laryngoscopy could permanently damage the spinal

cord likely resulting in quadriplegia)

(There are numerous techniques (retrograde intubationhellip) purported

to involve less cervical spine motion each of which requires substantial skill and experience These should only be attempted by

experienced practitioners Some advocate in-line stabilization where a second person attempts to hold the cervical spine still while

the primary person attempts direct laryngoscopy This technique makes intubation more difficult and is inadequate for stabilization)

mohammad reza rajabi

Page 29 432012

(While an attractive option many would argue that anytime a

regional anesthetic is planned immediate endotracheal intubation must be possible Complications may occur during the regional block

or it may be inadequate for the operation or wear off before the surgeons are done Therefore inability to emergently intubate a

patient is a relative contraindication to regional anesthesia and should be considered in this patient with a possible unstable neck)

(Great idea)

Cervical Spine Anatomy-Atlas

C1 The Atlas is a ring that interacts with the skull base above and

C2 shown on next page It is unique in that it lacks a vertebral body and spinous process The articulation of C1 with the occiput is very

tight providing little of the flexion of the cervical spine and only about 20 degrees of extension

mohammad reza rajabi

Page 30 432012

Cervical Spine Anatomy-Axis

C2 The Axis has an unusual thumb-like extension of its vertebral body that passes through the arch of C1 This process is called the

dens or odontoid The odontoid process is normally held very tightly against the anterior arch of C1 by the transverse ligament

Meanwhile the spinal cord travels behind the odontoid within the

arch of C1

mohammad reza rajabi

Page 31 432012

Atlanto Axial Joint

This atlanto-axial joint provides the majority of the rotational motion of the cervical spine Meanwhile flexion and extension are primarily

accomplished at C2 and below and particularly between C4 and C6

Neck Movement with DL

What happens to the neck during direct laryngoscopy and

intubation

As you have seen the sniffing position involves neck flexion in the lower cervical spine with extension superiorly In the process of

direct laryngoscopy this motion is accentuated As the laryngoscope

is lifted upward the occiput is extended primarily at the atlanto-occipital joint (occiput-C1) while flexion occurs at C2-3 and below

Therefore any intervention that impedes this flexion and extension

will make visualization of the glottis more difficult In someone with a cervical fusion up to the occiput it is pretty much impossible to

perform direct laryngoscopy Similarly a patient with external stabilization such as a c-collar in this case will (SHOULD) have neck

movement reduced sufficient to make visualization difficult if not impossible

mohammad reza rajabi

Page 32 432012

Clearing the C-Spine

How does one rule out damage to the cervical spine

At present history is our greatest ally If the healthy patient has no history of neck problems and no symptoms on maximal flexion and

extension they are unlikely to have cervical spine disease

On the other hand there are many patients whose cervical spine

SHOULD be radiographically evaluated pre-operatively including certain trauma patients as well as those with disease states that

affect the cervical spine including rheumatoid arthritis and Downs Syndrome These diseases may affect the transverse ligament and

thus the stability at the atlanto-axial joint

Nexus Criteria

Which trauma patients require cervical spine films prior to surgery or

intubation There is a set of criteria identified by the National Emergency X-

Radiography Utilization Study (NEXUS) that attempt to identify patients with a low probability of injury thereby reducing the

number of negative cervical spine radiographs taken

The criteria include No midline cervical tenderness

No focal neurologic deficit

Normal alertness

No intoxication

No painful distracting injury that might make them ignore their

neck pain

For those patients whose cervical spine is not cleared the

anesthesiologist must consider the risks of cervical spine damage that can be worsened through direct laryngoscopy versus the risk of

alternative techniques that may minimize neck motion including awake fiberoptic intubation A description of these alternate

techniques is beyond the scope of this site at present

mohammad reza rajabi

Page 33 432012

Spine Film

For the current case the following film is obtained

Patients Film

Normal for Comparison

mohammad reza rajabi

Page 34 432012

Explanation

Note the large step-off between C6 and C7 This subluxation causes entrapment of the spinal cord and damage

Therefore this patient requires an intubation technique with minimal neck motion and awake positioningas well as some external

stabilization or operative intervention to prevent damage to the spinal cord at the neck

mohammad reza rajabi

Page 35 432012

C-Spine Review

So which patients are at higher risk for neck injury during intubation

Trauma patients

Yes No

(yes)Correct

They may have trauma to the cervical spine as well

(no)Incorrect

They may have trauma to the cervical spine as well

Rheumatoid arthritis patients

Yes No

(yes)Correct

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

(no)Incorrect

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

Downs Syndrome patients

Yes No

(yes)Correct

About 15 of these patients have laxity in the transverse ligament

that holds the odontoid against the anterior arch of C1 Xrays are also recommended in these patients prior to anticipated neck

manipulation including laryngoscopy

mohammad reza rajabi

Page 36 432012

(no)Incorrect

About 15 of these patients have laxity in the transverse ligament that holds the odontoid against the anterior arch of C1 Xrays are

also recommended in these patients prior to anticipated neck manipulation including laryngoscopy

Osteoarthritic patients

Yes No

(yes)Incorrect

They are not at higher risk

(no)Correct

They are not at higher risk

Patient with a prior cervical spine fusion

Yes No

(yes)Incorrect

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

(no)Correct

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

mohammad reza rajabi

Page 37 432012

Airway References

Cricoid Pressure

Vanner RG Asai T Safe use of cricoid pressure Anaesthesia 1999 54 1-3 A review of literature with recommendations

Sellick BA Cricoid pressure to control regurgitation of stomach contents during induction of anaesthesia Lancet 1961 2 404-6 The original description

Views and Grades

Mallampati SR Gatt SP et al A clinical sign to predict difficult tracheal intubation a prospective study Can Anaesth Soc J 198532(4)429-434 The original paper describing the classification system but only 3 grades (III and IV combined)

Samsoon GLT and Young JRB Difficult tracheal intubation a retrospective study Anaesthesia 198742487-490 Describes the addition of Mallampati class 4

Cormack RS and Lehane J Difficult tracheal intubation in obstetrics Anaesthesia 1984391105-1111 Describes the laryngoscopy grades and correlates with difficult intubation Also proposes a technique of attempting to intubate while intentionally achieving a suboptimal (Class III) view

Studies of Predictive Indices

There are many studies some which counter others One difficulty is defining a difficult airway Most use a Cormack-Lehane laryngoscopy grade of III-IV Some investigate specific radiographic measurements that are impractical in daily clinical practice Below are a few useful references

El-Ganzouri AR McCarthy RJ et al Preoperative airway assessment Predictive value of a multivariate risk index Anesth Analg 1996821197-1204 A logistic regression comparing examination tests and developing a risk index

Chou HC Wu TL et al Mandibulohyoid distance in difficult laryngoscopy Br J Anaesth 1993 71335-339 A single article sighting this distance as an important factor in an analysis of only 11 patients

Frerk CM Predicting difficult intubation Anaesthesia 1991461005-1008 A study suggesting that a Mallampati Class III or IV with thyromental distance of lt7cm is sensitive and specific for difficult intubation (laryngoscopy grade 3 or 4)

C-Spine Evaluation

mohammad reza rajabi

Page 38 432012

Hoffman JR Mower WR et al Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma N Engl J Med 200034394-99 Application of the NEXUS criteria

mohammad reza rajabi

Page 25 432012

Purple

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(V)Yes

The maxillary branch (V2) supplies the nasal cavity and palate while the mandibular branch (V3) supplies the anterior 23 of the tongue

(IX)Incorrect

The glossopharyngeal nerve supplies sensation to the posterior 13

of the tongue and its overlying structures including the soft palate

(X)No

The vagus innervates the airway further distal

Green

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)Yes

The glossopharyngeal nerve supplies sensation to the posterior 13

of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(X)No

The vagus innervates the airway further distal

mohammad reza rajabi

Page 26 432012

Blue

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)No

The glossopharyngeal nerve supplies sensation to the posterior 13 of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(x)Yes but which branch

Internal branch of superior laryngeal

External branch of superior laryngeal

Recurrent laryngeal

(Yes

The Internal Branch of the Superior Laryngeal Nerve provides

sensory innervation to the mucous membrane from the epiglottis to

and including the vocal cords

Incorrect

The External Branch of the Superior Laryngeal nerve provides motor innervation to the cricothyroid muscle only

Incorrect

The Recurrent Laryngeal Nerve supplies sensory innervation to the

trachea below the vocal cords as well as motor innervation to all the

intrinsic muscles of the larynx except the cricothyroid muscle)

mohammad reza rajabi

Page 27 432012

Red

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)No

The glossopharyngeal nerve supplies sensation to the posterior 13 of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(x)Yes but which branch

Internal branch of superior laryngeal

External branch of superior laryngeal

Recurrent laryngeal

(Incorrect

The Internal Branch of the Superior Laryngeal Nerve provides sensory innervation to the mucous membrane from the epiglottis to

and including the vocal cords

Incorrect

The External Branch of the Superior Laryngeal nerve provides motor innervation to the cricothyroid muscle only

Yes

The Recurrent Laryngeal Nerve supplies sensory innervation to the

trachea below the vocal cords as well as motor innervation to all the

intrinsic muscles of the larynx except the cricothyroid muscle)

mohammad reza rajabi

Page 28 432012

Case 3 Spine Evaluation

A previously healthy 40-year-old male presents with an open femur fracture from a Motor Vehicle Accident (MVA) that needs to be

repaired under general anesthesia He is currently on a backboard

with a cervical collar in place and is hemodynamically stable

Examination of this patients airway is complicated by the presence of the cervical collar which both inhibits mouth opening and by

definition prevents neck extension As you have seen above neck extension is required for direct laryngoscopy

So what shall we do

Remove the neck collar and intubate as usual

Intubate with a technique that does not require neck movement

Avoid general anesthesia and perform a regional block for the

procedure

Perform studies to clear the cervical spine

First a basic review of the anatomy is helpful

Recall that the cervical spine consists of 7 vertebrae the first two of

which are highly specialized

(Should this patient have an unstable cervical spine the movement resulting from laryngoscopy could permanently damage the spinal

cord likely resulting in quadriplegia)

(There are numerous techniques (retrograde intubationhellip) purported

to involve less cervical spine motion each of which requires substantial skill and experience These should only be attempted by

experienced practitioners Some advocate in-line stabilization where a second person attempts to hold the cervical spine still while

the primary person attempts direct laryngoscopy This technique makes intubation more difficult and is inadequate for stabilization)

mohammad reza rajabi

Page 29 432012

(While an attractive option many would argue that anytime a

regional anesthetic is planned immediate endotracheal intubation must be possible Complications may occur during the regional block

or it may be inadequate for the operation or wear off before the surgeons are done Therefore inability to emergently intubate a

patient is a relative contraindication to regional anesthesia and should be considered in this patient with a possible unstable neck)

(Great idea)

Cervical Spine Anatomy-Atlas

C1 The Atlas is a ring that interacts with the skull base above and

C2 shown on next page It is unique in that it lacks a vertebral body and spinous process The articulation of C1 with the occiput is very

tight providing little of the flexion of the cervical spine and only about 20 degrees of extension

mohammad reza rajabi

Page 30 432012

Cervical Spine Anatomy-Axis

C2 The Axis has an unusual thumb-like extension of its vertebral body that passes through the arch of C1 This process is called the

dens or odontoid The odontoid process is normally held very tightly against the anterior arch of C1 by the transverse ligament

Meanwhile the spinal cord travels behind the odontoid within the

arch of C1

mohammad reza rajabi

Page 31 432012

Atlanto Axial Joint

This atlanto-axial joint provides the majority of the rotational motion of the cervical spine Meanwhile flexion and extension are primarily

accomplished at C2 and below and particularly between C4 and C6

Neck Movement with DL

What happens to the neck during direct laryngoscopy and

intubation

As you have seen the sniffing position involves neck flexion in the lower cervical spine with extension superiorly In the process of

direct laryngoscopy this motion is accentuated As the laryngoscope

is lifted upward the occiput is extended primarily at the atlanto-occipital joint (occiput-C1) while flexion occurs at C2-3 and below

Therefore any intervention that impedes this flexion and extension

will make visualization of the glottis more difficult In someone with a cervical fusion up to the occiput it is pretty much impossible to

perform direct laryngoscopy Similarly a patient with external stabilization such as a c-collar in this case will (SHOULD) have neck

movement reduced sufficient to make visualization difficult if not impossible

mohammad reza rajabi

Page 32 432012

Clearing the C-Spine

How does one rule out damage to the cervical spine

At present history is our greatest ally If the healthy patient has no history of neck problems and no symptoms on maximal flexion and

extension they are unlikely to have cervical spine disease

On the other hand there are many patients whose cervical spine

SHOULD be radiographically evaluated pre-operatively including certain trauma patients as well as those with disease states that

affect the cervical spine including rheumatoid arthritis and Downs Syndrome These diseases may affect the transverse ligament and

thus the stability at the atlanto-axial joint

Nexus Criteria

Which trauma patients require cervical spine films prior to surgery or

intubation There is a set of criteria identified by the National Emergency X-

Radiography Utilization Study (NEXUS) that attempt to identify patients with a low probability of injury thereby reducing the

number of negative cervical spine radiographs taken

The criteria include No midline cervical tenderness

No focal neurologic deficit

Normal alertness

No intoxication

No painful distracting injury that might make them ignore their

neck pain

For those patients whose cervical spine is not cleared the

anesthesiologist must consider the risks of cervical spine damage that can be worsened through direct laryngoscopy versus the risk of

alternative techniques that may minimize neck motion including awake fiberoptic intubation A description of these alternate

techniques is beyond the scope of this site at present

mohammad reza rajabi

Page 33 432012

Spine Film

For the current case the following film is obtained

Patients Film

Normal for Comparison

mohammad reza rajabi

Page 34 432012

Explanation

Note the large step-off between C6 and C7 This subluxation causes entrapment of the spinal cord and damage

Therefore this patient requires an intubation technique with minimal neck motion and awake positioningas well as some external

stabilization or operative intervention to prevent damage to the spinal cord at the neck

mohammad reza rajabi

Page 35 432012

C-Spine Review

So which patients are at higher risk for neck injury during intubation

Trauma patients

Yes No

(yes)Correct

They may have trauma to the cervical spine as well

(no)Incorrect

They may have trauma to the cervical spine as well

Rheumatoid arthritis patients

Yes No

(yes)Correct

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

(no)Incorrect

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

Downs Syndrome patients

Yes No

(yes)Correct

About 15 of these patients have laxity in the transverse ligament

that holds the odontoid against the anterior arch of C1 Xrays are also recommended in these patients prior to anticipated neck

manipulation including laryngoscopy

mohammad reza rajabi

Page 36 432012

(no)Incorrect

About 15 of these patients have laxity in the transverse ligament that holds the odontoid against the anterior arch of C1 Xrays are

also recommended in these patients prior to anticipated neck manipulation including laryngoscopy

Osteoarthritic patients

Yes No

(yes)Incorrect

They are not at higher risk

(no)Correct

They are not at higher risk

Patient with a prior cervical spine fusion

Yes No

(yes)Incorrect

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

(no)Correct

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

mohammad reza rajabi

Page 37 432012

Airway References

Cricoid Pressure

Vanner RG Asai T Safe use of cricoid pressure Anaesthesia 1999 54 1-3 A review of literature with recommendations

Sellick BA Cricoid pressure to control regurgitation of stomach contents during induction of anaesthesia Lancet 1961 2 404-6 The original description

Views and Grades

Mallampati SR Gatt SP et al A clinical sign to predict difficult tracheal intubation a prospective study Can Anaesth Soc J 198532(4)429-434 The original paper describing the classification system but only 3 grades (III and IV combined)

Samsoon GLT and Young JRB Difficult tracheal intubation a retrospective study Anaesthesia 198742487-490 Describes the addition of Mallampati class 4

Cormack RS and Lehane J Difficult tracheal intubation in obstetrics Anaesthesia 1984391105-1111 Describes the laryngoscopy grades and correlates with difficult intubation Also proposes a technique of attempting to intubate while intentionally achieving a suboptimal (Class III) view

Studies of Predictive Indices

There are many studies some which counter others One difficulty is defining a difficult airway Most use a Cormack-Lehane laryngoscopy grade of III-IV Some investigate specific radiographic measurements that are impractical in daily clinical practice Below are a few useful references

El-Ganzouri AR McCarthy RJ et al Preoperative airway assessment Predictive value of a multivariate risk index Anesth Analg 1996821197-1204 A logistic regression comparing examination tests and developing a risk index

Chou HC Wu TL et al Mandibulohyoid distance in difficult laryngoscopy Br J Anaesth 1993 71335-339 A single article sighting this distance as an important factor in an analysis of only 11 patients

Frerk CM Predicting difficult intubation Anaesthesia 1991461005-1008 A study suggesting that a Mallampati Class III or IV with thyromental distance of lt7cm is sensitive and specific for difficult intubation (laryngoscopy grade 3 or 4)

C-Spine Evaluation

mohammad reza rajabi

Page 38 432012

Hoffman JR Mower WR et al Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma N Engl J Med 200034394-99 Application of the NEXUS criteria

mohammad reza rajabi

Page 26 432012

Blue

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)No

The glossopharyngeal nerve supplies sensation to the posterior 13 of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(x)Yes but which branch

Internal branch of superior laryngeal

External branch of superior laryngeal

Recurrent laryngeal

(Yes

The Internal Branch of the Superior Laryngeal Nerve provides

sensory innervation to the mucous membrane from the epiglottis to

and including the vocal cords

Incorrect

The External Branch of the Superior Laryngeal nerve provides motor innervation to the cricothyroid muscle only

Incorrect

The Recurrent Laryngeal Nerve supplies sensory innervation to the

trachea below the vocal cords as well as motor innervation to all the

intrinsic muscles of the larynx except the cricothyroid muscle)

mohammad reza rajabi

Page 27 432012

Red

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)No

The glossopharyngeal nerve supplies sensation to the posterior 13 of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(x)Yes but which branch

Internal branch of superior laryngeal

External branch of superior laryngeal

Recurrent laryngeal

(Incorrect

The Internal Branch of the Superior Laryngeal Nerve provides sensory innervation to the mucous membrane from the epiglottis to

and including the vocal cords

Incorrect

The External Branch of the Superior Laryngeal nerve provides motor innervation to the cricothyroid muscle only

Yes

The Recurrent Laryngeal Nerve supplies sensory innervation to the

trachea below the vocal cords as well as motor innervation to all the

intrinsic muscles of the larynx except the cricothyroid muscle)

mohammad reza rajabi

Page 28 432012

Case 3 Spine Evaluation

A previously healthy 40-year-old male presents with an open femur fracture from a Motor Vehicle Accident (MVA) that needs to be

repaired under general anesthesia He is currently on a backboard

with a cervical collar in place and is hemodynamically stable

Examination of this patients airway is complicated by the presence of the cervical collar which both inhibits mouth opening and by

definition prevents neck extension As you have seen above neck extension is required for direct laryngoscopy

So what shall we do

Remove the neck collar and intubate as usual

Intubate with a technique that does not require neck movement

Avoid general anesthesia and perform a regional block for the

procedure

Perform studies to clear the cervical spine

First a basic review of the anatomy is helpful

Recall that the cervical spine consists of 7 vertebrae the first two of

which are highly specialized

(Should this patient have an unstable cervical spine the movement resulting from laryngoscopy could permanently damage the spinal

cord likely resulting in quadriplegia)

(There are numerous techniques (retrograde intubationhellip) purported

to involve less cervical spine motion each of which requires substantial skill and experience These should only be attempted by

experienced practitioners Some advocate in-line stabilization where a second person attempts to hold the cervical spine still while

the primary person attempts direct laryngoscopy This technique makes intubation more difficult and is inadequate for stabilization)

mohammad reza rajabi

Page 29 432012

(While an attractive option many would argue that anytime a

regional anesthetic is planned immediate endotracheal intubation must be possible Complications may occur during the regional block

or it may be inadequate for the operation or wear off before the surgeons are done Therefore inability to emergently intubate a

patient is a relative contraindication to regional anesthesia and should be considered in this patient with a possible unstable neck)

(Great idea)

Cervical Spine Anatomy-Atlas

C1 The Atlas is a ring that interacts with the skull base above and

C2 shown on next page It is unique in that it lacks a vertebral body and spinous process The articulation of C1 with the occiput is very

tight providing little of the flexion of the cervical spine and only about 20 degrees of extension

mohammad reza rajabi

Page 30 432012

Cervical Spine Anatomy-Axis

C2 The Axis has an unusual thumb-like extension of its vertebral body that passes through the arch of C1 This process is called the

dens or odontoid The odontoid process is normally held very tightly against the anterior arch of C1 by the transverse ligament

Meanwhile the spinal cord travels behind the odontoid within the

arch of C1

mohammad reza rajabi

Page 31 432012

Atlanto Axial Joint

This atlanto-axial joint provides the majority of the rotational motion of the cervical spine Meanwhile flexion and extension are primarily

accomplished at C2 and below and particularly between C4 and C6

Neck Movement with DL

What happens to the neck during direct laryngoscopy and

intubation

As you have seen the sniffing position involves neck flexion in the lower cervical spine with extension superiorly In the process of

direct laryngoscopy this motion is accentuated As the laryngoscope

is lifted upward the occiput is extended primarily at the atlanto-occipital joint (occiput-C1) while flexion occurs at C2-3 and below

Therefore any intervention that impedes this flexion and extension

will make visualization of the glottis more difficult In someone with a cervical fusion up to the occiput it is pretty much impossible to

perform direct laryngoscopy Similarly a patient with external stabilization such as a c-collar in this case will (SHOULD) have neck

movement reduced sufficient to make visualization difficult if not impossible

mohammad reza rajabi

Page 32 432012

Clearing the C-Spine

How does one rule out damage to the cervical spine

At present history is our greatest ally If the healthy patient has no history of neck problems and no symptoms on maximal flexion and

extension they are unlikely to have cervical spine disease

On the other hand there are many patients whose cervical spine

SHOULD be radiographically evaluated pre-operatively including certain trauma patients as well as those with disease states that

affect the cervical spine including rheumatoid arthritis and Downs Syndrome These diseases may affect the transverse ligament and

thus the stability at the atlanto-axial joint

Nexus Criteria

Which trauma patients require cervical spine films prior to surgery or

intubation There is a set of criteria identified by the National Emergency X-

Radiography Utilization Study (NEXUS) that attempt to identify patients with a low probability of injury thereby reducing the

number of negative cervical spine radiographs taken

The criteria include No midline cervical tenderness

No focal neurologic deficit

Normal alertness

No intoxication

No painful distracting injury that might make them ignore their

neck pain

For those patients whose cervical spine is not cleared the

anesthesiologist must consider the risks of cervical spine damage that can be worsened through direct laryngoscopy versus the risk of

alternative techniques that may minimize neck motion including awake fiberoptic intubation A description of these alternate

techniques is beyond the scope of this site at present

mohammad reza rajabi

Page 33 432012

Spine Film

For the current case the following film is obtained

Patients Film

Normal for Comparison

mohammad reza rajabi

Page 34 432012

Explanation

Note the large step-off between C6 and C7 This subluxation causes entrapment of the spinal cord and damage

Therefore this patient requires an intubation technique with minimal neck motion and awake positioningas well as some external

stabilization or operative intervention to prevent damage to the spinal cord at the neck

mohammad reza rajabi

Page 35 432012

C-Spine Review

So which patients are at higher risk for neck injury during intubation

Trauma patients

Yes No

(yes)Correct

They may have trauma to the cervical spine as well

(no)Incorrect

They may have trauma to the cervical spine as well

Rheumatoid arthritis patients

Yes No

(yes)Correct

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

(no)Incorrect

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

Downs Syndrome patients

Yes No

(yes)Correct

About 15 of these patients have laxity in the transverse ligament

that holds the odontoid against the anterior arch of C1 Xrays are also recommended in these patients prior to anticipated neck

manipulation including laryngoscopy

mohammad reza rajabi

Page 36 432012

(no)Incorrect

About 15 of these patients have laxity in the transverse ligament that holds the odontoid against the anterior arch of C1 Xrays are

also recommended in these patients prior to anticipated neck manipulation including laryngoscopy

Osteoarthritic patients

Yes No

(yes)Incorrect

They are not at higher risk

(no)Correct

They are not at higher risk

Patient with a prior cervical spine fusion

Yes No

(yes)Incorrect

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

(no)Correct

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

mohammad reza rajabi

Page 37 432012

Airway References

Cricoid Pressure

Vanner RG Asai T Safe use of cricoid pressure Anaesthesia 1999 54 1-3 A review of literature with recommendations

Sellick BA Cricoid pressure to control regurgitation of stomach contents during induction of anaesthesia Lancet 1961 2 404-6 The original description

Views and Grades

Mallampati SR Gatt SP et al A clinical sign to predict difficult tracheal intubation a prospective study Can Anaesth Soc J 198532(4)429-434 The original paper describing the classification system but only 3 grades (III and IV combined)

Samsoon GLT and Young JRB Difficult tracheal intubation a retrospective study Anaesthesia 198742487-490 Describes the addition of Mallampati class 4

Cormack RS and Lehane J Difficult tracheal intubation in obstetrics Anaesthesia 1984391105-1111 Describes the laryngoscopy grades and correlates with difficult intubation Also proposes a technique of attempting to intubate while intentionally achieving a suboptimal (Class III) view

Studies of Predictive Indices

There are many studies some which counter others One difficulty is defining a difficult airway Most use a Cormack-Lehane laryngoscopy grade of III-IV Some investigate specific radiographic measurements that are impractical in daily clinical practice Below are a few useful references

El-Ganzouri AR McCarthy RJ et al Preoperative airway assessment Predictive value of a multivariate risk index Anesth Analg 1996821197-1204 A logistic regression comparing examination tests and developing a risk index

Chou HC Wu TL et al Mandibulohyoid distance in difficult laryngoscopy Br J Anaesth 1993 71335-339 A single article sighting this distance as an important factor in an analysis of only 11 patients

Frerk CM Predicting difficult intubation Anaesthesia 1991461005-1008 A study suggesting that a Mallampati Class III or IV with thyromental distance of lt7cm is sensitive and specific for difficult intubation (laryngoscopy grade 3 or 4)

C-Spine Evaluation

mohammad reza rajabi

Page 38 432012

Hoffman JR Mower WR et al Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma N Engl J Med 200034394-99 Application of the NEXUS criteria

mohammad reza rajabi

Page 27 432012

Red

Facial (VII) Trigeminal (V)

Glossopharyngeal (IX) Vagus (X)

(VII)No

The Facial Nerve supplies only taste to the tongue

(IX)No

The glossopharyngeal nerve supplies sensation to the posterior 13 of the tongue and its overlying structures including the soft palate

(V)No

The maxillary branch (V2) supplies the nasal cavity and palate while

the mandibular branch (V3) supplies the anterior 23 of the tongue

(x)Yes but which branch

Internal branch of superior laryngeal

External branch of superior laryngeal

Recurrent laryngeal

(Incorrect

The Internal Branch of the Superior Laryngeal Nerve provides sensory innervation to the mucous membrane from the epiglottis to

and including the vocal cords

Incorrect

The External Branch of the Superior Laryngeal nerve provides motor innervation to the cricothyroid muscle only

Yes

The Recurrent Laryngeal Nerve supplies sensory innervation to the

trachea below the vocal cords as well as motor innervation to all the

intrinsic muscles of the larynx except the cricothyroid muscle)

mohammad reza rajabi

Page 28 432012

Case 3 Spine Evaluation

A previously healthy 40-year-old male presents with an open femur fracture from a Motor Vehicle Accident (MVA) that needs to be

repaired under general anesthesia He is currently on a backboard

with a cervical collar in place and is hemodynamically stable

Examination of this patients airway is complicated by the presence of the cervical collar which both inhibits mouth opening and by

definition prevents neck extension As you have seen above neck extension is required for direct laryngoscopy

So what shall we do

Remove the neck collar and intubate as usual

Intubate with a technique that does not require neck movement

Avoid general anesthesia and perform a regional block for the

procedure

Perform studies to clear the cervical spine

First a basic review of the anatomy is helpful

Recall that the cervical spine consists of 7 vertebrae the first two of

which are highly specialized

(Should this patient have an unstable cervical spine the movement resulting from laryngoscopy could permanently damage the spinal

cord likely resulting in quadriplegia)

(There are numerous techniques (retrograde intubationhellip) purported

to involve less cervical spine motion each of which requires substantial skill and experience These should only be attempted by

experienced practitioners Some advocate in-line stabilization where a second person attempts to hold the cervical spine still while

the primary person attempts direct laryngoscopy This technique makes intubation more difficult and is inadequate for stabilization)

mohammad reza rajabi

Page 29 432012

(While an attractive option many would argue that anytime a

regional anesthetic is planned immediate endotracheal intubation must be possible Complications may occur during the regional block

or it may be inadequate for the operation or wear off before the surgeons are done Therefore inability to emergently intubate a

patient is a relative contraindication to regional anesthesia and should be considered in this patient with a possible unstable neck)

(Great idea)

Cervical Spine Anatomy-Atlas

C1 The Atlas is a ring that interacts with the skull base above and

C2 shown on next page It is unique in that it lacks a vertebral body and spinous process The articulation of C1 with the occiput is very

tight providing little of the flexion of the cervical spine and only about 20 degrees of extension

mohammad reza rajabi

Page 30 432012

Cervical Spine Anatomy-Axis

C2 The Axis has an unusual thumb-like extension of its vertebral body that passes through the arch of C1 This process is called the

dens or odontoid The odontoid process is normally held very tightly against the anterior arch of C1 by the transverse ligament

Meanwhile the spinal cord travels behind the odontoid within the

arch of C1

mohammad reza rajabi

Page 31 432012

Atlanto Axial Joint

This atlanto-axial joint provides the majority of the rotational motion of the cervical spine Meanwhile flexion and extension are primarily

accomplished at C2 and below and particularly between C4 and C6

Neck Movement with DL

What happens to the neck during direct laryngoscopy and

intubation

As you have seen the sniffing position involves neck flexion in the lower cervical spine with extension superiorly In the process of

direct laryngoscopy this motion is accentuated As the laryngoscope

is lifted upward the occiput is extended primarily at the atlanto-occipital joint (occiput-C1) while flexion occurs at C2-3 and below

Therefore any intervention that impedes this flexion and extension

will make visualization of the glottis more difficult In someone with a cervical fusion up to the occiput it is pretty much impossible to

perform direct laryngoscopy Similarly a patient with external stabilization such as a c-collar in this case will (SHOULD) have neck

movement reduced sufficient to make visualization difficult if not impossible

mohammad reza rajabi

Page 32 432012

Clearing the C-Spine

How does one rule out damage to the cervical spine

At present history is our greatest ally If the healthy patient has no history of neck problems and no symptoms on maximal flexion and

extension they are unlikely to have cervical spine disease

On the other hand there are many patients whose cervical spine

SHOULD be radiographically evaluated pre-operatively including certain trauma patients as well as those with disease states that

affect the cervical spine including rheumatoid arthritis and Downs Syndrome These diseases may affect the transverse ligament and

thus the stability at the atlanto-axial joint

Nexus Criteria

Which trauma patients require cervical spine films prior to surgery or

intubation There is a set of criteria identified by the National Emergency X-

Radiography Utilization Study (NEXUS) that attempt to identify patients with a low probability of injury thereby reducing the

number of negative cervical spine radiographs taken

The criteria include No midline cervical tenderness

No focal neurologic deficit

Normal alertness

No intoxication

No painful distracting injury that might make them ignore their

neck pain

For those patients whose cervical spine is not cleared the

anesthesiologist must consider the risks of cervical spine damage that can be worsened through direct laryngoscopy versus the risk of

alternative techniques that may minimize neck motion including awake fiberoptic intubation A description of these alternate

techniques is beyond the scope of this site at present

mohammad reza rajabi

Page 33 432012

Spine Film

For the current case the following film is obtained

Patients Film

Normal for Comparison

mohammad reza rajabi

Page 34 432012

Explanation

Note the large step-off between C6 and C7 This subluxation causes entrapment of the spinal cord and damage

Therefore this patient requires an intubation technique with minimal neck motion and awake positioningas well as some external

stabilization or operative intervention to prevent damage to the spinal cord at the neck

mohammad reza rajabi

Page 35 432012

C-Spine Review

So which patients are at higher risk for neck injury during intubation

Trauma patients

Yes No

(yes)Correct

They may have trauma to the cervical spine as well

(no)Incorrect

They may have trauma to the cervical spine as well

Rheumatoid arthritis patients

Yes No

(yes)Correct

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

(no)Incorrect

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

Downs Syndrome patients

Yes No

(yes)Correct

About 15 of these patients have laxity in the transverse ligament

that holds the odontoid against the anterior arch of C1 Xrays are also recommended in these patients prior to anticipated neck

manipulation including laryngoscopy

mohammad reza rajabi

Page 36 432012

(no)Incorrect

About 15 of these patients have laxity in the transverse ligament that holds the odontoid against the anterior arch of C1 Xrays are

also recommended in these patients prior to anticipated neck manipulation including laryngoscopy

Osteoarthritic patients

Yes No

(yes)Incorrect

They are not at higher risk

(no)Correct

They are not at higher risk

Patient with a prior cervical spine fusion

Yes No

(yes)Incorrect

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

(no)Correct

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

mohammad reza rajabi

Page 37 432012

Airway References

Cricoid Pressure

Vanner RG Asai T Safe use of cricoid pressure Anaesthesia 1999 54 1-3 A review of literature with recommendations

Sellick BA Cricoid pressure to control regurgitation of stomach contents during induction of anaesthesia Lancet 1961 2 404-6 The original description

Views and Grades

Mallampati SR Gatt SP et al A clinical sign to predict difficult tracheal intubation a prospective study Can Anaesth Soc J 198532(4)429-434 The original paper describing the classification system but only 3 grades (III and IV combined)

Samsoon GLT and Young JRB Difficult tracheal intubation a retrospective study Anaesthesia 198742487-490 Describes the addition of Mallampati class 4

Cormack RS and Lehane J Difficult tracheal intubation in obstetrics Anaesthesia 1984391105-1111 Describes the laryngoscopy grades and correlates with difficult intubation Also proposes a technique of attempting to intubate while intentionally achieving a suboptimal (Class III) view

Studies of Predictive Indices

There are many studies some which counter others One difficulty is defining a difficult airway Most use a Cormack-Lehane laryngoscopy grade of III-IV Some investigate specific radiographic measurements that are impractical in daily clinical practice Below are a few useful references

El-Ganzouri AR McCarthy RJ et al Preoperative airway assessment Predictive value of a multivariate risk index Anesth Analg 1996821197-1204 A logistic regression comparing examination tests and developing a risk index

Chou HC Wu TL et al Mandibulohyoid distance in difficult laryngoscopy Br J Anaesth 1993 71335-339 A single article sighting this distance as an important factor in an analysis of only 11 patients

Frerk CM Predicting difficult intubation Anaesthesia 1991461005-1008 A study suggesting that a Mallampati Class III or IV with thyromental distance of lt7cm is sensitive and specific for difficult intubation (laryngoscopy grade 3 or 4)

C-Spine Evaluation

mohammad reza rajabi

Page 38 432012

Hoffman JR Mower WR et al Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma N Engl J Med 200034394-99 Application of the NEXUS criteria

mohammad reza rajabi

Page 28 432012

Case 3 Spine Evaluation

A previously healthy 40-year-old male presents with an open femur fracture from a Motor Vehicle Accident (MVA) that needs to be

repaired under general anesthesia He is currently on a backboard

with a cervical collar in place and is hemodynamically stable

Examination of this patients airway is complicated by the presence of the cervical collar which both inhibits mouth opening and by

definition prevents neck extension As you have seen above neck extension is required for direct laryngoscopy

So what shall we do

Remove the neck collar and intubate as usual

Intubate with a technique that does not require neck movement

Avoid general anesthesia and perform a regional block for the

procedure

Perform studies to clear the cervical spine

First a basic review of the anatomy is helpful

Recall that the cervical spine consists of 7 vertebrae the first two of

which are highly specialized

(Should this patient have an unstable cervical spine the movement resulting from laryngoscopy could permanently damage the spinal

cord likely resulting in quadriplegia)

(There are numerous techniques (retrograde intubationhellip) purported

to involve less cervical spine motion each of which requires substantial skill and experience These should only be attempted by

experienced practitioners Some advocate in-line stabilization where a second person attempts to hold the cervical spine still while

the primary person attempts direct laryngoscopy This technique makes intubation more difficult and is inadequate for stabilization)

mohammad reza rajabi

Page 29 432012

(While an attractive option many would argue that anytime a

regional anesthetic is planned immediate endotracheal intubation must be possible Complications may occur during the regional block

or it may be inadequate for the operation or wear off before the surgeons are done Therefore inability to emergently intubate a

patient is a relative contraindication to regional anesthesia and should be considered in this patient with a possible unstable neck)

(Great idea)

Cervical Spine Anatomy-Atlas

C1 The Atlas is a ring that interacts with the skull base above and

C2 shown on next page It is unique in that it lacks a vertebral body and spinous process The articulation of C1 with the occiput is very

tight providing little of the flexion of the cervical spine and only about 20 degrees of extension

mohammad reza rajabi

Page 30 432012

Cervical Spine Anatomy-Axis

C2 The Axis has an unusual thumb-like extension of its vertebral body that passes through the arch of C1 This process is called the

dens or odontoid The odontoid process is normally held very tightly against the anterior arch of C1 by the transverse ligament

Meanwhile the spinal cord travels behind the odontoid within the

arch of C1

mohammad reza rajabi

Page 31 432012

Atlanto Axial Joint

This atlanto-axial joint provides the majority of the rotational motion of the cervical spine Meanwhile flexion and extension are primarily

accomplished at C2 and below and particularly between C4 and C6

Neck Movement with DL

What happens to the neck during direct laryngoscopy and

intubation

As you have seen the sniffing position involves neck flexion in the lower cervical spine with extension superiorly In the process of

direct laryngoscopy this motion is accentuated As the laryngoscope

is lifted upward the occiput is extended primarily at the atlanto-occipital joint (occiput-C1) while flexion occurs at C2-3 and below

Therefore any intervention that impedes this flexion and extension

will make visualization of the glottis more difficult In someone with a cervical fusion up to the occiput it is pretty much impossible to

perform direct laryngoscopy Similarly a patient with external stabilization such as a c-collar in this case will (SHOULD) have neck

movement reduced sufficient to make visualization difficult if not impossible

mohammad reza rajabi

Page 32 432012

Clearing the C-Spine

How does one rule out damage to the cervical spine

At present history is our greatest ally If the healthy patient has no history of neck problems and no symptoms on maximal flexion and

extension they are unlikely to have cervical spine disease

On the other hand there are many patients whose cervical spine

SHOULD be radiographically evaluated pre-operatively including certain trauma patients as well as those with disease states that

affect the cervical spine including rheumatoid arthritis and Downs Syndrome These diseases may affect the transverse ligament and

thus the stability at the atlanto-axial joint

Nexus Criteria

Which trauma patients require cervical spine films prior to surgery or

intubation There is a set of criteria identified by the National Emergency X-

Radiography Utilization Study (NEXUS) that attempt to identify patients with a low probability of injury thereby reducing the

number of negative cervical spine radiographs taken

The criteria include No midline cervical tenderness

No focal neurologic deficit

Normal alertness

No intoxication

No painful distracting injury that might make them ignore their

neck pain

For those patients whose cervical spine is not cleared the

anesthesiologist must consider the risks of cervical spine damage that can be worsened through direct laryngoscopy versus the risk of

alternative techniques that may minimize neck motion including awake fiberoptic intubation A description of these alternate

techniques is beyond the scope of this site at present

mohammad reza rajabi

Page 33 432012

Spine Film

For the current case the following film is obtained

Patients Film

Normal for Comparison

mohammad reza rajabi

Page 34 432012

Explanation

Note the large step-off between C6 and C7 This subluxation causes entrapment of the spinal cord and damage

Therefore this patient requires an intubation technique with minimal neck motion and awake positioningas well as some external

stabilization or operative intervention to prevent damage to the spinal cord at the neck

mohammad reza rajabi

Page 35 432012

C-Spine Review

So which patients are at higher risk for neck injury during intubation

Trauma patients

Yes No

(yes)Correct

They may have trauma to the cervical spine as well

(no)Incorrect

They may have trauma to the cervical spine as well

Rheumatoid arthritis patients

Yes No

(yes)Correct

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

(no)Incorrect

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

Downs Syndrome patients

Yes No

(yes)Correct

About 15 of these patients have laxity in the transverse ligament

that holds the odontoid against the anterior arch of C1 Xrays are also recommended in these patients prior to anticipated neck

manipulation including laryngoscopy

mohammad reza rajabi

Page 36 432012

(no)Incorrect

About 15 of these patients have laxity in the transverse ligament that holds the odontoid against the anterior arch of C1 Xrays are

also recommended in these patients prior to anticipated neck manipulation including laryngoscopy

Osteoarthritic patients

Yes No

(yes)Incorrect

They are not at higher risk

(no)Correct

They are not at higher risk

Patient with a prior cervical spine fusion

Yes No

(yes)Incorrect

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

(no)Correct

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

mohammad reza rajabi

Page 37 432012

Airway References

Cricoid Pressure

Vanner RG Asai T Safe use of cricoid pressure Anaesthesia 1999 54 1-3 A review of literature with recommendations

Sellick BA Cricoid pressure to control regurgitation of stomach contents during induction of anaesthesia Lancet 1961 2 404-6 The original description

Views and Grades

Mallampati SR Gatt SP et al A clinical sign to predict difficult tracheal intubation a prospective study Can Anaesth Soc J 198532(4)429-434 The original paper describing the classification system but only 3 grades (III and IV combined)

Samsoon GLT and Young JRB Difficult tracheal intubation a retrospective study Anaesthesia 198742487-490 Describes the addition of Mallampati class 4

Cormack RS and Lehane J Difficult tracheal intubation in obstetrics Anaesthesia 1984391105-1111 Describes the laryngoscopy grades and correlates with difficult intubation Also proposes a technique of attempting to intubate while intentionally achieving a suboptimal (Class III) view

Studies of Predictive Indices

There are many studies some which counter others One difficulty is defining a difficult airway Most use a Cormack-Lehane laryngoscopy grade of III-IV Some investigate specific radiographic measurements that are impractical in daily clinical practice Below are a few useful references

El-Ganzouri AR McCarthy RJ et al Preoperative airway assessment Predictive value of a multivariate risk index Anesth Analg 1996821197-1204 A logistic regression comparing examination tests and developing a risk index

Chou HC Wu TL et al Mandibulohyoid distance in difficult laryngoscopy Br J Anaesth 1993 71335-339 A single article sighting this distance as an important factor in an analysis of only 11 patients

Frerk CM Predicting difficult intubation Anaesthesia 1991461005-1008 A study suggesting that a Mallampati Class III or IV with thyromental distance of lt7cm is sensitive and specific for difficult intubation (laryngoscopy grade 3 or 4)

C-Spine Evaluation

mohammad reza rajabi

Page 38 432012

Hoffman JR Mower WR et al Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma N Engl J Med 200034394-99 Application of the NEXUS criteria

mohammad reza rajabi

Page 29 432012

(While an attractive option many would argue that anytime a

regional anesthetic is planned immediate endotracheal intubation must be possible Complications may occur during the regional block

or it may be inadequate for the operation or wear off before the surgeons are done Therefore inability to emergently intubate a

patient is a relative contraindication to regional anesthesia and should be considered in this patient with a possible unstable neck)

(Great idea)

Cervical Spine Anatomy-Atlas

C1 The Atlas is a ring that interacts with the skull base above and

C2 shown on next page It is unique in that it lacks a vertebral body and spinous process The articulation of C1 with the occiput is very

tight providing little of the flexion of the cervical spine and only about 20 degrees of extension

mohammad reza rajabi

Page 30 432012

Cervical Spine Anatomy-Axis

C2 The Axis has an unusual thumb-like extension of its vertebral body that passes through the arch of C1 This process is called the

dens or odontoid The odontoid process is normally held very tightly against the anterior arch of C1 by the transverse ligament

Meanwhile the spinal cord travels behind the odontoid within the

arch of C1

mohammad reza rajabi

Page 31 432012

Atlanto Axial Joint

This atlanto-axial joint provides the majority of the rotational motion of the cervical spine Meanwhile flexion and extension are primarily

accomplished at C2 and below and particularly between C4 and C6

Neck Movement with DL

What happens to the neck during direct laryngoscopy and

intubation

As you have seen the sniffing position involves neck flexion in the lower cervical spine with extension superiorly In the process of

direct laryngoscopy this motion is accentuated As the laryngoscope

is lifted upward the occiput is extended primarily at the atlanto-occipital joint (occiput-C1) while flexion occurs at C2-3 and below

Therefore any intervention that impedes this flexion and extension

will make visualization of the glottis more difficult In someone with a cervical fusion up to the occiput it is pretty much impossible to

perform direct laryngoscopy Similarly a patient with external stabilization such as a c-collar in this case will (SHOULD) have neck

movement reduced sufficient to make visualization difficult if not impossible

mohammad reza rajabi

Page 32 432012

Clearing the C-Spine

How does one rule out damage to the cervical spine

At present history is our greatest ally If the healthy patient has no history of neck problems and no symptoms on maximal flexion and

extension they are unlikely to have cervical spine disease

On the other hand there are many patients whose cervical spine

SHOULD be radiographically evaluated pre-operatively including certain trauma patients as well as those with disease states that

affect the cervical spine including rheumatoid arthritis and Downs Syndrome These diseases may affect the transverse ligament and

thus the stability at the atlanto-axial joint

Nexus Criteria

Which trauma patients require cervical spine films prior to surgery or

intubation There is a set of criteria identified by the National Emergency X-

Radiography Utilization Study (NEXUS) that attempt to identify patients with a low probability of injury thereby reducing the

number of negative cervical spine radiographs taken

The criteria include No midline cervical tenderness

No focal neurologic deficit

Normal alertness

No intoxication

No painful distracting injury that might make them ignore their

neck pain

For those patients whose cervical spine is not cleared the

anesthesiologist must consider the risks of cervical spine damage that can be worsened through direct laryngoscopy versus the risk of

alternative techniques that may minimize neck motion including awake fiberoptic intubation A description of these alternate

techniques is beyond the scope of this site at present

mohammad reza rajabi

Page 33 432012

Spine Film

For the current case the following film is obtained

Patients Film

Normal for Comparison

mohammad reza rajabi

Page 34 432012

Explanation

Note the large step-off between C6 and C7 This subluxation causes entrapment of the spinal cord and damage

Therefore this patient requires an intubation technique with minimal neck motion and awake positioningas well as some external

stabilization or operative intervention to prevent damage to the spinal cord at the neck

mohammad reza rajabi

Page 35 432012

C-Spine Review

So which patients are at higher risk for neck injury during intubation

Trauma patients

Yes No

(yes)Correct

They may have trauma to the cervical spine as well

(no)Incorrect

They may have trauma to the cervical spine as well

Rheumatoid arthritis patients

Yes No

(yes)Correct

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

(no)Incorrect

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

Downs Syndrome patients

Yes No

(yes)Correct

About 15 of these patients have laxity in the transverse ligament

that holds the odontoid against the anterior arch of C1 Xrays are also recommended in these patients prior to anticipated neck

manipulation including laryngoscopy

mohammad reza rajabi

Page 36 432012

(no)Incorrect

About 15 of these patients have laxity in the transverse ligament that holds the odontoid against the anterior arch of C1 Xrays are

also recommended in these patients prior to anticipated neck manipulation including laryngoscopy

Osteoarthritic patients

Yes No

(yes)Incorrect

They are not at higher risk

(no)Correct

They are not at higher risk

Patient with a prior cervical spine fusion

Yes No

(yes)Incorrect

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

(no)Correct

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

mohammad reza rajabi

Page 37 432012

Airway References

Cricoid Pressure

Vanner RG Asai T Safe use of cricoid pressure Anaesthesia 1999 54 1-3 A review of literature with recommendations

Sellick BA Cricoid pressure to control regurgitation of stomach contents during induction of anaesthesia Lancet 1961 2 404-6 The original description

Views and Grades

Mallampati SR Gatt SP et al A clinical sign to predict difficult tracheal intubation a prospective study Can Anaesth Soc J 198532(4)429-434 The original paper describing the classification system but only 3 grades (III and IV combined)

Samsoon GLT and Young JRB Difficult tracheal intubation a retrospective study Anaesthesia 198742487-490 Describes the addition of Mallampati class 4

Cormack RS and Lehane J Difficult tracheal intubation in obstetrics Anaesthesia 1984391105-1111 Describes the laryngoscopy grades and correlates with difficult intubation Also proposes a technique of attempting to intubate while intentionally achieving a suboptimal (Class III) view

Studies of Predictive Indices

There are many studies some which counter others One difficulty is defining a difficult airway Most use a Cormack-Lehane laryngoscopy grade of III-IV Some investigate specific radiographic measurements that are impractical in daily clinical practice Below are a few useful references

El-Ganzouri AR McCarthy RJ et al Preoperative airway assessment Predictive value of a multivariate risk index Anesth Analg 1996821197-1204 A logistic regression comparing examination tests and developing a risk index

Chou HC Wu TL et al Mandibulohyoid distance in difficult laryngoscopy Br J Anaesth 1993 71335-339 A single article sighting this distance as an important factor in an analysis of only 11 patients

Frerk CM Predicting difficult intubation Anaesthesia 1991461005-1008 A study suggesting that a Mallampati Class III or IV with thyromental distance of lt7cm is sensitive and specific for difficult intubation (laryngoscopy grade 3 or 4)

C-Spine Evaluation

mohammad reza rajabi

Page 38 432012

Hoffman JR Mower WR et al Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma N Engl J Med 200034394-99 Application of the NEXUS criteria

mohammad reza rajabi

Page 30 432012

Cervical Spine Anatomy-Axis

C2 The Axis has an unusual thumb-like extension of its vertebral body that passes through the arch of C1 This process is called the

dens or odontoid The odontoid process is normally held very tightly against the anterior arch of C1 by the transverse ligament

Meanwhile the spinal cord travels behind the odontoid within the

arch of C1

mohammad reza rajabi

Page 31 432012

Atlanto Axial Joint

This atlanto-axial joint provides the majority of the rotational motion of the cervical spine Meanwhile flexion and extension are primarily

accomplished at C2 and below and particularly between C4 and C6

Neck Movement with DL

What happens to the neck during direct laryngoscopy and

intubation

As you have seen the sniffing position involves neck flexion in the lower cervical spine with extension superiorly In the process of

direct laryngoscopy this motion is accentuated As the laryngoscope

is lifted upward the occiput is extended primarily at the atlanto-occipital joint (occiput-C1) while flexion occurs at C2-3 and below

Therefore any intervention that impedes this flexion and extension

will make visualization of the glottis more difficult In someone with a cervical fusion up to the occiput it is pretty much impossible to

perform direct laryngoscopy Similarly a patient with external stabilization such as a c-collar in this case will (SHOULD) have neck

movement reduced sufficient to make visualization difficult if not impossible

mohammad reza rajabi

Page 32 432012

Clearing the C-Spine

How does one rule out damage to the cervical spine

At present history is our greatest ally If the healthy patient has no history of neck problems and no symptoms on maximal flexion and

extension they are unlikely to have cervical spine disease

On the other hand there are many patients whose cervical spine

SHOULD be radiographically evaluated pre-operatively including certain trauma patients as well as those with disease states that

affect the cervical spine including rheumatoid arthritis and Downs Syndrome These diseases may affect the transverse ligament and

thus the stability at the atlanto-axial joint

Nexus Criteria

Which trauma patients require cervical spine films prior to surgery or

intubation There is a set of criteria identified by the National Emergency X-

Radiography Utilization Study (NEXUS) that attempt to identify patients with a low probability of injury thereby reducing the

number of negative cervical spine radiographs taken

The criteria include No midline cervical tenderness

No focal neurologic deficit

Normal alertness

No intoxication

No painful distracting injury that might make them ignore their

neck pain

For those patients whose cervical spine is not cleared the

anesthesiologist must consider the risks of cervical spine damage that can be worsened through direct laryngoscopy versus the risk of

alternative techniques that may minimize neck motion including awake fiberoptic intubation A description of these alternate

techniques is beyond the scope of this site at present

mohammad reza rajabi

Page 33 432012

Spine Film

For the current case the following film is obtained

Patients Film

Normal for Comparison

mohammad reza rajabi

Page 34 432012

Explanation

Note the large step-off between C6 and C7 This subluxation causes entrapment of the spinal cord and damage

Therefore this patient requires an intubation technique with minimal neck motion and awake positioningas well as some external

stabilization or operative intervention to prevent damage to the spinal cord at the neck

mohammad reza rajabi

Page 35 432012

C-Spine Review

So which patients are at higher risk for neck injury during intubation

Trauma patients

Yes No

(yes)Correct

They may have trauma to the cervical spine as well

(no)Incorrect

They may have trauma to the cervical spine as well

Rheumatoid arthritis patients

Yes No

(yes)Correct

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

(no)Incorrect

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

Downs Syndrome patients

Yes No

(yes)Correct

About 15 of these patients have laxity in the transverse ligament

that holds the odontoid against the anterior arch of C1 Xrays are also recommended in these patients prior to anticipated neck

manipulation including laryngoscopy

mohammad reza rajabi

Page 36 432012

(no)Incorrect

About 15 of these patients have laxity in the transverse ligament that holds the odontoid against the anterior arch of C1 Xrays are

also recommended in these patients prior to anticipated neck manipulation including laryngoscopy

Osteoarthritic patients

Yes No

(yes)Incorrect

They are not at higher risk

(no)Correct

They are not at higher risk

Patient with a prior cervical spine fusion

Yes No

(yes)Incorrect

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

(no)Correct

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

mohammad reza rajabi

Page 37 432012

Airway References

Cricoid Pressure

Vanner RG Asai T Safe use of cricoid pressure Anaesthesia 1999 54 1-3 A review of literature with recommendations

Sellick BA Cricoid pressure to control regurgitation of stomach contents during induction of anaesthesia Lancet 1961 2 404-6 The original description

Views and Grades

Mallampati SR Gatt SP et al A clinical sign to predict difficult tracheal intubation a prospective study Can Anaesth Soc J 198532(4)429-434 The original paper describing the classification system but only 3 grades (III and IV combined)

Samsoon GLT and Young JRB Difficult tracheal intubation a retrospective study Anaesthesia 198742487-490 Describes the addition of Mallampati class 4

Cormack RS and Lehane J Difficult tracheal intubation in obstetrics Anaesthesia 1984391105-1111 Describes the laryngoscopy grades and correlates with difficult intubation Also proposes a technique of attempting to intubate while intentionally achieving a suboptimal (Class III) view

Studies of Predictive Indices

There are many studies some which counter others One difficulty is defining a difficult airway Most use a Cormack-Lehane laryngoscopy grade of III-IV Some investigate specific radiographic measurements that are impractical in daily clinical practice Below are a few useful references

El-Ganzouri AR McCarthy RJ et al Preoperative airway assessment Predictive value of a multivariate risk index Anesth Analg 1996821197-1204 A logistic regression comparing examination tests and developing a risk index

Chou HC Wu TL et al Mandibulohyoid distance in difficult laryngoscopy Br J Anaesth 1993 71335-339 A single article sighting this distance as an important factor in an analysis of only 11 patients

Frerk CM Predicting difficult intubation Anaesthesia 1991461005-1008 A study suggesting that a Mallampati Class III or IV with thyromental distance of lt7cm is sensitive and specific for difficult intubation (laryngoscopy grade 3 or 4)

C-Spine Evaluation

mohammad reza rajabi

Page 38 432012

Hoffman JR Mower WR et al Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma N Engl J Med 200034394-99 Application of the NEXUS criteria

mohammad reza rajabi

Page 31 432012

Atlanto Axial Joint

This atlanto-axial joint provides the majority of the rotational motion of the cervical spine Meanwhile flexion and extension are primarily

accomplished at C2 and below and particularly between C4 and C6

Neck Movement with DL

What happens to the neck during direct laryngoscopy and

intubation

As you have seen the sniffing position involves neck flexion in the lower cervical spine with extension superiorly In the process of

direct laryngoscopy this motion is accentuated As the laryngoscope

is lifted upward the occiput is extended primarily at the atlanto-occipital joint (occiput-C1) while flexion occurs at C2-3 and below

Therefore any intervention that impedes this flexion and extension

will make visualization of the glottis more difficult In someone with a cervical fusion up to the occiput it is pretty much impossible to

perform direct laryngoscopy Similarly a patient with external stabilization such as a c-collar in this case will (SHOULD) have neck

movement reduced sufficient to make visualization difficult if not impossible

mohammad reza rajabi

Page 32 432012

Clearing the C-Spine

How does one rule out damage to the cervical spine

At present history is our greatest ally If the healthy patient has no history of neck problems and no symptoms on maximal flexion and

extension they are unlikely to have cervical spine disease

On the other hand there are many patients whose cervical spine

SHOULD be radiographically evaluated pre-operatively including certain trauma patients as well as those with disease states that

affect the cervical spine including rheumatoid arthritis and Downs Syndrome These diseases may affect the transverse ligament and

thus the stability at the atlanto-axial joint

Nexus Criteria

Which trauma patients require cervical spine films prior to surgery or

intubation There is a set of criteria identified by the National Emergency X-

Radiography Utilization Study (NEXUS) that attempt to identify patients with a low probability of injury thereby reducing the

number of negative cervical spine radiographs taken

The criteria include No midline cervical tenderness

No focal neurologic deficit

Normal alertness

No intoxication

No painful distracting injury that might make them ignore their

neck pain

For those patients whose cervical spine is not cleared the

anesthesiologist must consider the risks of cervical spine damage that can be worsened through direct laryngoscopy versus the risk of

alternative techniques that may minimize neck motion including awake fiberoptic intubation A description of these alternate

techniques is beyond the scope of this site at present

mohammad reza rajabi

Page 33 432012

Spine Film

For the current case the following film is obtained

Patients Film

Normal for Comparison

mohammad reza rajabi

Page 34 432012

Explanation

Note the large step-off between C6 and C7 This subluxation causes entrapment of the spinal cord and damage

Therefore this patient requires an intubation technique with minimal neck motion and awake positioningas well as some external

stabilization or operative intervention to prevent damage to the spinal cord at the neck

mohammad reza rajabi

Page 35 432012

C-Spine Review

So which patients are at higher risk for neck injury during intubation

Trauma patients

Yes No

(yes)Correct

They may have trauma to the cervical spine as well

(no)Incorrect

They may have trauma to the cervical spine as well

Rheumatoid arthritis patients

Yes No

(yes)Correct

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

(no)Incorrect

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

Downs Syndrome patients

Yes No

(yes)Correct

About 15 of these patients have laxity in the transverse ligament

that holds the odontoid against the anterior arch of C1 Xrays are also recommended in these patients prior to anticipated neck

manipulation including laryngoscopy

mohammad reza rajabi

Page 36 432012

(no)Incorrect

About 15 of these patients have laxity in the transverse ligament that holds the odontoid against the anterior arch of C1 Xrays are

also recommended in these patients prior to anticipated neck manipulation including laryngoscopy

Osteoarthritic patients

Yes No

(yes)Incorrect

They are not at higher risk

(no)Correct

They are not at higher risk

Patient with a prior cervical spine fusion

Yes No

(yes)Incorrect

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

(no)Correct

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

mohammad reza rajabi

Page 37 432012

Airway References

Cricoid Pressure

Vanner RG Asai T Safe use of cricoid pressure Anaesthesia 1999 54 1-3 A review of literature with recommendations

Sellick BA Cricoid pressure to control regurgitation of stomach contents during induction of anaesthesia Lancet 1961 2 404-6 The original description

Views and Grades

Mallampati SR Gatt SP et al A clinical sign to predict difficult tracheal intubation a prospective study Can Anaesth Soc J 198532(4)429-434 The original paper describing the classification system but only 3 grades (III and IV combined)

Samsoon GLT and Young JRB Difficult tracheal intubation a retrospective study Anaesthesia 198742487-490 Describes the addition of Mallampati class 4

Cormack RS and Lehane J Difficult tracheal intubation in obstetrics Anaesthesia 1984391105-1111 Describes the laryngoscopy grades and correlates with difficult intubation Also proposes a technique of attempting to intubate while intentionally achieving a suboptimal (Class III) view

Studies of Predictive Indices

There are many studies some which counter others One difficulty is defining a difficult airway Most use a Cormack-Lehane laryngoscopy grade of III-IV Some investigate specific radiographic measurements that are impractical in daily clinical practice Below are a few useful references

El-Ganzouri AR McCarthy RJ et al Preoperative airway assessment Predictive value of a multivariate risk index Anesth Analg 1996821197-1204 A logistic regression comparing examination tests and developing a risk index

Chou HC Wu TL et al Mandibulohyoid distance in difficult laryngoscopy Br J Anaesth 1993 71335-339 A single article sighting this distance as an important factor in an analysis of only 11 patients

Frerk CM Predicting difficult intubation Anaesthesia 1991461005-1008 A study suggesting that a Mallampati Class III or IV with thyromental distance of lt7cm is sensitive and specific for difficult intubation (laryngoscopy grade 3 or 4)

C-Spine Evaluation

mohammad reza rajabi

Page 38 432012

Hoffman JR Mower WR et al Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma N Engl J Med 200034394-99 Application of the NEXUS criteria

mohammad reza rajabi

Page 32 432012

Clearing the C-Spine

How does one rule out damage to the cervical spine

At present history is our greatest ally If the healthy patient has no history of neck problems and no symptoms on maximal flexion and

extension they are unlikely to have cervical spine disease

On the other hand there are many patients whose cervical spine

SHOULD be radiographically evaluated pre-operatively including certain trauma patients as well as those with disease states that

affect the cervical spine including rheumatoid arthritis and Downs Syndrome These diseases may affect the transverse ligament and

thus the stability at the atlanto-axial joint

Nexus Criteria

Which trauma patients require cervical spine films prior to surgery or

intubation There is a set of criteria identified by the National Emergency X-

Radiography Utilization Study (NEXUS) that attempt to identify patients with a low probability of injury thereby reducing the

number of negative cervical spine radiographs taken

The criteria include No midline cervical tenderness

No focal neurologic deficit

Normal alertness

No intoxication

No painful distracting injury that might make them ignore their

neck pain

For those patients whose cervical spine is not cleared the

anesthesiologist must consider the risks of cervical spine damage that can be worsened through direct laryngoscopy versus the risk of

alternative techniques that may minimize neck motion including awake fiberoptic intubation A description of these alternate

techniques is beyond the scope of this site at present

mohammad reza rajabi

Page 33 432012

Spine Film

For the current case the following film is obtained

Patients Film

Normal for Comparison

mohammad reza rajabi

Page 34 432012

Explanation

Note the large step-off between C6 and C7 This subluxation causes entrapment of the spinal cord and damage

Therefore this patient requires an intubation technique with minimal neck motion and awake positioningas well as some external

stabilization or operative intervention to prevent damage to the spinal cord at the neck

mohammad reza rajabi

Page 35 432012

C-Spine Review

So which patients are at higher risk for neck injury during intubation

Trauma patients

Yes No

(yes)Correct

They may have trauma to the cervical spine as well

(no)Incorrect

They may have trauma to the cervical spine as well

Rheumatoid arthritis patients

Yes No

(yes)Correct

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

(no)Incorrect

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

Downs Syndrome patients

Yes No

(yes)Correct

About 15 of these patients have laxity in the transverse ligament

that holds the odontoid against the anterior arch of C1 Xrays are also recommended in these patients prior to anticipated neck

manipulation including laryngoscopy

mohammad reza rajabi

Page 36 432012

(no)Incorrect

About 15 of these patients have laxity in the transverse ligament that holds the odontoid against the anterior arch of C1 Xrays are

also recommended in these patients prior to anticipated neck manipulation including laryngoscopy

Osteoarthritic patients

Yes No

(yes)Incorrect

They are not at higher risk

(no)Correct

They are not at higher risk

Patient with a prior cervical spine fusion

Yes No

(yes)Incorrect

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

(no)Correct

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

mohammad reza rajabi

Page 37 432012

Airway References

Cricoid Pressure

Vanner RG Asai T Safe use of cricoid pressure Anaesthesia 1999 54 1-3 A review of literature with recommendations

Sellick BA Cricoid pressure to control regurgitation of stomach contents during induction of anaesthesia Lancet 1961 2 404-6 The original description

Views and Grades

Mallampati SR Gatt SP et al A clinical sign to predict difficult tracheal intubation a prospective study Can Anaesth Soc J 198532(4)429-434 The original paper describing the classification system but only 3 grades (III and IV combined)

Samsoon GLT and Young JRB Difficult tracheal intubation a retrospective study Anaesthesia 198742487-490 Describes the addition of Mallampati class 4

Cormack RS and Lehane J Difficult tracheal intubation in obstetrics Anaesthesia 1984391105-1111 Describes the laryngoscopy grades and correlates with difficult intubation Also proposes a technique of attempting to intubate while intentionally achieving a suboptimal (Class III) view

Studies of Predictive Indices

There are many studies some which counter others One difficulty is defining a difficult airway Most use a Cormack-Lehane laryngoscopy grade of III-IV Some investigate specific radiographic measurements that are impractical in daily clinical practice Below are a few useful references

El-Ganzouri AR McCarthy RJ et al Preoperative airway assessment Predictive value of a multivariate risk index Anesth Analg 1996821197-1204 A logistic regression comparing examination tests and developing a risk index

Chou HC Wu TL et al Mandibulohyoid distance in difficult laryngoscopy Br J Anaesth 1993 71335-339 A single article sighting this distance as an important factor in an analysis of only 11 patients

Frerk CM Predicting difficult intubation Anaesthesia 1991461005-1008 A study suggesting that a Mallampati Class III or IV with thyromental distance of lt7cm is sensitive and specific for difficult intubation (laryngoscopy grade 3 or 4)

C-Spine Evaluation

mohammad reza rajabi

Page 38 432012

Hoffman JR Mower WR et al Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma N Engl J Med 200034394-99 Application of the NEXUS criteria

mohammad reza rajabi

Page 33 432012

Spine Film

For the current case the following film is obtained

Patients Film

Normal for Comparison

mohammad reza rajabi

Page 34 432012

Explanation

Note the large step-off between C6 and C7 This subluxation causes entrapment of the spinal cord and damage

Therefore this patient requires an intubation technique with minimal neck motion and awake positioningas well as some external

stabilization or operative intervention to prevent damage to the spinal cord at the neck

mohammad reza rajabi

Page 35 432012

C-Spine Review

So which patients are at higher risk for neck injury during intubation

Trauma patients

Yes No

(yes)Correct

They may have trauma to the cervical spine as well

(no)Incorrect

They may have trauma to the cervical spine as well

Rheumatoid arthritis patients

Yes No

(yes)Correct

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

(no)Incorrect

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

Downs Syndrome patients

Yes No

(yes)Correct

About 15 of these patients have laxity in the transverse ligament

that holds the odontoid against the anterior arch of C1 Xrays are also recommended in these patients prior to anticipated neck

manipulation including laryngoscopy

mohammad reza rajabi

Page 36 432012

(no)Incorrect

About 15 of these patients have laxity in the transverse ligament that holds the odontoid against the anterior arch of C1 Xrays are

also recommended in these patients prior to anticipated neck manipulation including laryngoscopy

Osteoarthritic patients

Yes No

(yes)Incorrect

They are not at higher risk

(no)Correct

They are not at higher risk

Patient with a prior cervical spine fusion

Yes No

(yes)Incorrect

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

(no)Correct

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

mohammad reza rajabi

Page 37 432012

Airway References

Cricoid Pressure

Vanner RG Asai T Safe use of cricoid pressure Anaesthesia 1999 54 1-3 A review of literature with recommendations

Sellick BA Cricoid pressure to control regurgitation of stomach contents during induction of anaesthesia Lancet 1961 2 404-6 The original description

Views and Grades

Mallampati SR Gatt SP et al A clinical sign to predict difficult tracheal intubation a prospective study Can Anaesth Soc J 198532(4)429-434 The original paper describing the classification system but only 3 grades (III and IV combined)

Samsoon GLT and Young JRB Difficult tracheal intubation a retrospective study Anaesthesia 198742487-490 Describes the addition of Mallampati class 4

Cormack RS and Lehane J Difficult tracheal intubation in obstetrics Anaesthesia 1984391105-1111 Describes the laryngoscopy grades and correlates with difficult intubation Also proposes a technique of attempting to intubate while intentionally achieving a suboptimal (Class III) view

Studies of Predictive Indices

There are many studies some which counter others One difficulty is defining a difficult airway Most use a Cormack-Lehane laryngoscopy grade of III-IV Some investigate specific radiographic measurements that are impractical in daily clinical practice Below are a few useful references

El-Ganzouri AR McCarthy RJ et al Preoperative airway assessment Predictive value of a multivariate risk index Anesth Analg 1996821197-1204 A logistic regression comparing examination tests and developing a risk index

Chou HC Wu TL et al Mandibulohyoid distance in difficult laryngoscopy Br J Anaesth 1993 71335-339 A single article sighting this distance as an important factor in an analysis of only 11 patients

Frerk CM Predicting difficult intubation Anaesthesia 1991461005-1008 A study suggesting that a Mallampati Class III or IV with thyromental distance of lt7cm is sensitive and specific for difficult intubation (laryngoscopy grade 3 or 4)

C-Spine Evaluation

mohammad reza rajabi

Page 38 432012

Hoffman JR Mower WR et al Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma N Engl J Med 200034394-99 Application of the NEXUS criteria

mohammad reza rajabi

Page 34 432012

Explanation

Note the large step-off between C6 and C7 This subluxation causes entrapment of the spinal cord and damage

Therefore this patient requires an intubation technique with minimal neck motion and awake positioningas well as some external

stabilization or operative intervention to prevent damage to the spinal cord at the neck

mohammad reza rajabi

Page 35 432012

C-Spine Review

So which patients are at higher risk for neck injury during intubation

Trauma patients

Yes No

(yes)Correct

They may have trauma to the cervical spine as well

(no)Incorrect

They may have trauma to the cervical spine as well

Rheumatoid arthritis patients

Yes No

(yes)Correct

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

(no)Incorrect

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

Downs Syndrome patients

Yes No

(yes)Correct

About 15 of these patients have laxity in the transverse ligament

that holds the odontoid against the anterior arch of C1 Xrays are also recommended in these patients prior to anticipated neck

manipulation including laryngoscopy

mohammad reza rajabi

Page 36 432012

(no)Incorrect

About 15 of these patients have laxity in the transverse ligament that holds the odontoid against the anterior arch of C1 Xrays are

also recommended in these patients prior to anticipated neck manipulation including laryngoscopy

Osteoarthritic patients

Yes No

(yes)Incorrect

They are not at higher risk

(no)Correct

They are not at higher risk

Patient with a prior cervical spine fusion

Yes No

(yes)Incorrect

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

(no)Correct

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

mohammad reza rajabi

Page 37 432012

Airway References

Cricoid Pressure

Vanner RG Asai T Safe use of cricoid pressure Anaesthesia 1999 54 1-3 A review of literature with recommendations

Sellick BA Cricoid pressure to control regurgitation of stomach contents during induction of anaesthesia Lancet 1961 2 404-6 The original description

Views and Grades

Mallampati SR Gatt SP et al A clinical sign to predict difficult tracheal intubation a prospective study Can Anaesth Soc J 198532(4)429-434 The original paper describing the classification system but only 3 grades (III and IV combined)

Samsoon GLT and Young JRB Difficult tracheal intubation a retrospective study Anaesthesia 198742487-490 Describes the addition of Mallampati class 4

Cormack RS and Lehane J Difficult tracheal intubation in obstetrics Anaesthesia 1984391105-1111 Describes the laryngoscopy grades and correlates with difficult intubation Also proposes a technique of attempting to intubate while intentionally achieving a suboptimal (Class III) view

Studies of Predictive Indices

There are many studies some which counter others One difficulty is defining a difficult airway Most use a Cormack-Lehane laryngoscopy grade of III-IV Some investigate specific radiographic measurements that are impractical in daily clinical practice Below are a few useful references

El-Ganzouri AR McCarthy RJ et al Preoperative airway assessment Predictive value of a multivariate risk index Anesth Analg 1996821197-1204 A logistic regression comparing examination tests and developing a risk index

Chou HC Wu TL et al Mandibulohyoid distance in difficult laryngoscopy Br J Anaesth 1993 71335-339 A single article sighting this distance as an important factor in an analysis of only 11 patients

Frerk CM Predicting difficult intubation Anaesthesia 1991461005-1008 A study suggesting that a Mallampati Class III or IV with thyromental distance of lt7cm is sensitive and specific for difficult intubation (laryngoscopy grade 3 or 4)

C-Spine Evaluation

mohammad reza rajabi

Page 38 432012

Hoffman JR Mower WR et al Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma N Engl J Med 200034394-99 Application of the NEXUS criteria

mohammad reza rajabi

Page 35 432012

C-Spine Review

So which patients are at higher risk for neck injury during intubation

Trauma patients

Yes No

(yes)Correct

They may have trauma to the cervical spine as well

(no)Incorrect

They may have trauma to the cervical spine as well

Rheumatoid arthritis patients

Yes No

(yes)Correct

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

(no)Incorrect

Approximately 30 of patients with severe disease will have some

instability at C1-C2 All should have periodic flexion or extension xrays particularly prior to surgery

Downs Syndrome patients

Yes No

(yes)Correct

About 15 of these patients have laxity in the transverse ligament

that holds the odontoid against the anterior arch of C1 Xrays are also recommended in these patients prior to anticipated neck

manipulation including laryngoscopy

mohammad reza rajabi

Page 36 432012

(no)Incorrect

About 15 of these patients have laxity in the transverse ligament that holds the odontoid against the anterior arch of C1 Xrays are

also recommended in these patients prior to anticipated neck manipulation including laryngoscopy

Osteoarthritic patients

Yes No

(yes)Incorrect

They are not at higher risk

(no)Correct

They are not at higher risk

Patient with a prior cervical spine fusion

Yes No

(yes)Incorrect

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

(no)Correct

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

mohammad reza rajabi

Page 37 432012

Airway References

Cricoid Pressure

Vanner RG Asai T Safe use of cricoid pressure Anaesthesia 1999 54 1-3 A review of literature with recommendations

Sellick BA Cricoid pressure to control regurgitation of stomach contents during induction of anaesthesia Lancet 1961 2 404-6 The original description

Views and Grades

Mallampati SR Gatt SP et al A clinical sign to predict difficult tracheal intubation a prospective study Can Anaesth Soc J 198532(4)429-434 The original paper describing the classification system but only 3 grades (III and IV combined)

Samsoon GLT and Young JRB Difficult tracheal intubation a retrospective study Anaesthesia 198742487-490 Describes the addition of Mallampati class 4

Cormack RS and Lehane J Difficult tracheal intubation in obstetrics Anaesthesia 1984391105-1111 Describes the laryngoscopy grades and correlates with difficult intubation Also proposes a technique of attempting to intubate while intentionally achieving a suboptimal (Class III) view

Studies of Predictive Indices

There are many studies some which counter others One difficulty is defining a difficult airway Most use a Cormack-Lehane laryngoscopy grade of III-IV Some investigate specific radiographic measurements that are impractical in daily clinical practice Below are a few useful references

El-Ganzouri AR McCarthy RJ et al Preoperative airway assessment Predictive value of a multivariate risk index Anesth Analg 1996821197-1204 A logistic regression comparing examination tests and developing a risk index

Chou HC Wu TL et al Mandibulohyoid distance in difficult laryngoscopy Br J Anaesth 1993 71335-339 A single article sighting this distance as an important factor in an analysis of only 11 patients

Frerk CM Predicting difficult intubation Anaesthesia 1991461005-1008 A study suggesting that a Mallampati Class III or IV with thyromental distance of lt7cm is sensitive and specific for difficult intubation (laryngoscopy grade 3 or 4)

C-Spine Evaluation

mohammad reza rajabi

Page 38 432012

Hoffman JR Mower WR et al Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma N Engl J Med 200034394-99 Application of the NEXUS criteria

mohammad reza rajabi

Page 36 432012

(no)Incorrect

About 15 of these patients have laxity in the transverse ligament that holds the odontoid against the anterior arch of C1 Xrays are

also recommended in these patients prior to anticipated neck manipulation including laryngoscopy

Osteoarthritic patients

Yes No

(yes)Incorrect

They are not at higher risk

(no)Correct

They are not at higher risk

Patient with a prior cervical spine fusion

Yes No

(yes)Incorrect

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

(no)Correct

Assuming the repair is stable and there is no further disease there is

little risk of damage Such patients may be difficult to intubate though if their mobility is significantly limited

mohammad reza rajabi

Page 37 432012

Airway References

Cricoid Pressure

Vanner RG Asai T Safe use of cricoid pressure Anaesthesia 1999 54 1-3 A review of literature with recommendations

Sellick BA Cricoid pressure to control regurgitation of stomach contents during induction of anaesthesia Lancet 1961 2 404-6 The original description

Views and Grades

Mallampati SR Gatt SP et al A clinical sign to predict difficult tracheal intubation a prospective study Can Anaesth Soc J 198532(4)429-434 The original paper describing the classification system but only 3 grades (III and IV combined)

Samsoon GLT and Young JRB Difficult tracheal intubation a retrospective study Anaesthesia 198742487-490 Describes the addition of Mallampati class 4

Cormack RS and Lehane J Difficult tracheal intubation in obstetrics Anaesthesia 1984391105-1111 Describes the laryngoscopy grades and correlates with difficult intubation Also proposes a technique of attempting to intubate while intentionally achieving a suboptimal (Class III) view

Studies of Predictive Indices

There are many studies some which counter others One difficulty is defining a difficult airway Most use a Cormack-Lehane laryngoscopy grade of III-IV Some investigate specific radiographic measurements that are impractical in daily clinical practice Below are a few useful references

El-Ganzouri AR McCarthy RJ et al Preoperative airway assessment Predictive value of a multivariate risk index Anesth Analg 1996821197-1204 A logistic regression comparing examination tests and developing a risk index

Chou HC Wu TL et al Mandibulohyoid distance in difficult laryngoscopy Br J Anaesth 1993 71335-339 A single article sighting this distance as an important factor in an analysis of only 11 patients

Frerk CM Predicting difficult intubation Anaesthesia 1991461005-1008 A study suggesting that a Mallampati Class III or IV with thyromental distance of lt7cm is sensitive and specific for difficult intubation (laryngoscopy grade 3 or 4)

C-Spine Evaluation

mohammad reza rajabi

Page 38 432012

Hoffman JR Mower WR et al Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma N Engl J Med 200034394-99 Application of the NEXUS criteria

mohammad reza rajabi

Page 37 432012

Airway References

Cricoid Pressure

Vanner RG Asai T Safe use of cricoid pressure Anaesthesia 1999 54 1-3 A review of literature with recommendations

Sellick BA Cricoid pressure to control regurgitation of stomach contents during induction of anaesthesia Lancet 1961 2 404-6 The original description

Views and Grades

Mallampati SR Gatt SP et al A clinical sign to predict difficult tracheal intubation a prospective study Can Anaesth Soc J 198532(4)429-434 The original paper describing the classification system but only 3 grades (III and IV combined)

Samsoon GLT and Young JRB Difficult tracheal intubation a retrospective study Anaesthesia 198742487-490 Describes the addition of Mallampati class 4

Cormack RS and Lehane J Difficult tracheal intubation in obstetrics Anaesthesia 1984391105-1111 Describes the laryngoscopy grades and correlates with difficult intubation Also proposes a technique of attempting to intubate while intentionally achieving a suboptimal (Class III) view

Studies of Predictive Indices

There are many studies some which counter others One difficulty is defining a difficult airway Most use a Cormack-Lehane laryngoscopy grade of III-IV Some investigate specific radiographic measurements that are impractical in daily clinical practice Below are a few useful references

El-Ganzouri AR McCarthy RJ et al Preoperative airway assessment Predictive value of a multivariate risk index Anesth Analg 1996821197-1204 A logistic regression comparing examination tests and developing a risk index

Chou HC Wu TL et al Mandibulohyoid distance in difficult laryngoscopy Br J Anaesth 1993 71335-339 A single article sighting this distance as an important factor in an analysis of only 11 patients

Frerk CM Predicting difficult intubation Anaesthesia 1991461005-1008 A study suggesting that a Mallampati Class III or IV with thyromental distance of lt7cm is sensitive and specific for difficult intubation (laryngoscopy grade 3 or 4)

C-Spine Evaluation

mohammad reza rajabi

Page 38 432012

Hoffman JR Mower WR et al Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma N Engl J Med 200034394-99 Application of the NEXUS criteria

mohammad reza rajabi

Page 38 432012

Hoffman JR Mower WR et al Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma N Engl J Med 200034394-99 Application of the NEXUS criteria