Local Anesthetics 5

8/14/2019 Local Anesthetics 5

1/117

Local Anesthetics


2/117

2

General principles

Chemistry.

Esters-Procaine

-Chloroprocaine-Tetratcaine

-Cocaine

Metabolism-Hydrolysis by pseudo-

cholinesterase enzyme

Amides-Lidocaine

-Mepivacaine-Bupivacaine

-Etidocaine

-Prilocaine

-Ropivacaine

Metabolism-Liver


3/117

3

General principles

B.Mechanism of action 1.Local anesthetics block nerve conduction

2. Local anesthetics interact directly with

specific receptors on Na+ channel3. Physiochemical properties

High lipid solubilityprotein binding

pKa

Lower pH of the drug solution

4.Differential blockade of nerve fibers5. Sequence of clinical anesthesia.

6. Pathophysiologic factors .


4/117

4

Clinical uses of local anesthetics

The drugs in common use are

lignocaine, bupivacaine and prilocaine,

their characteristics are shown in Table.The choice of drug depends on the

speed of onset and duration of action

required. Epinephrine (adrenaline)

prolongs the latter.


5/117

5

Characteristics of local anaesthetic drugs

7

2

8

3

2

4

13

14

13

Lignocaine

Bupivacaine

Prilocaine

With

epinephrine

(mg/kg)

Plain

(mg/kg)

Duration

(h)

Agent

Maximum dose


6/117

6

Local anaesthetic drugs have serious side

effects if given in excess, or inadvertently released

into the circulation. Toxicity is manifested in avariety of ways ranging from mild excitation to

serious neurological and fatal cardiac sequelae.


7/117 7

Symptoms and signs of local anaesthetic toxicity

Anxiety Restlessness

Nausea

Tinnitus Circumoral tingling

Tremor

Tachypnoea

Clonic convulsions Arrhythmias

ventricular fibrillation

asystole


8/117 8

Recommendations for the safe use ofepinephrine in local anaesthetic solutions No hypoxia

No hypercapnia

Caution with arrhythmogenic volatile agents,for example, halothane

Concentration of 1:200,000

Dose


9/117 9

Requirements before starting regional

anaesthesia Informed consent

Vascular access Resuscitation drugs and equipment

Sterility of anaesthetist

Sterility of operative site

No contraindications to procedure Correct dosage of local anaesthetic drug


10/117 10

Epidural Spinal and Caudalanaesthesia


11/117 11

General considerations

A.Preoperative assessmentB. The area where the block is to be administered

should be examined

C. A history of abnormal bleeding

and a review of the patient's medicationsD. Patients should be given a detailed explanation

E. patients should receive appropriate monitoring

and have an intravenous (IV) line in place


12/117 12

Segmental level required for surgery

A knowledge of the sensory, motor, and autonomic

distribution of spinal nerves will help the anesthetist

determine the correct segmental level required for a

particular operation and help anticipate the potentialphysiologic effects of producing a block to that level.

illustrates the dermatomal distribution of the spinal

nerves.


13/117

13

Segmental level required for surgery

Key Dermatomes & Levels-C1-C2: Oops

-C3,4,5: Keep the diaphragm

alive

-T1-T4: Cardioaccelerator

-T4: Nipple line

-T6: Xyphoid process

-T10: Umbilicus-S2,3,4: Keep the penis

off the floor


14/117

14


15/117

15

A. Absolute1.Patient refusal.

2.Localized infection at skin puncture site.

3.Generalized sepsis (e.g., septicemia, bacteremia).

4.Coagulopathy.5.Increased intracranial pressure.

B. Relative

1.Localized infection peripheral to regional technique site

2.Hypovolemia.3.Central nervous system disease.

4.Chronic back pain.

Contraindications to peridural anesthesia


16/117

16

Section 1 Epidural anesthesia


17/117

17

Epidural anesthesiais achieved by introduction of anesthetics into

the epidural space.


18/117

18

Anatomy

The epidural space runs from the base of the skullto the bottom of the sacrum at the sacrococcygeal

membrane. The spinal cord, cerebrospinal fluid

and meninges are enclosed within it .


19/117

19

The spinal cord becomes the cauda equina at

the level of L2 in an adult and the cerebrospinal

fluid stops at the level of S2. The epidural space

is 36mm wide and is defined posteriorly by the

ligamentum flavum, the ante-rior surfaces of the

vertebral laminae, and the articular processes.

Anteriorly it is related to the posterior

longitudinal ligament and laterally is bounded bythe intervertebral foramenae and the pedicles.

Anatomy

33 Vertebra (inc 4 coccygeal)

Curvature(

L1 and S2 (end of cord/dura)

Angle of spinal processes


20/117


21/117

21

Anatomy

This is an accurate, and evencolorful representation of

the Epidural space in

relation to other structures

present in the vertebral area


22/117

22

Anatomy

The view from above

looking down, gives

an interesting perspective

on the planes traversed with

the epidural needle


23/117

23

Epidural anesthesia technique--Preparation

Obtain an epidural anesthesia kit

Check the contents of the kit for the

following items

-Skin local

-Test dose

-16-18g Husted or Touhy needle

-Glass syringe-Epidural catheter with adapter for

injection

-Various needles for local, seeker,

etc.


24/117

24


25/117

25

Epidural anesthesia techniquePositioning Sitting vs. lateral decubitis

-Most beginners do better sitting

-ALL patients should be on the monitor before starting

Encourage the patient to extrude their lower back

-Use yourself as an example

- Push your back out toward me, arched like a mad

cat

- pretend you are the worlds largest boiled shrimpThis will open up the interspace, help ID your landmarks, and

improve your chances


26/117

26


27/117

27

Epidural anesthesia technique

Approach

1.Midline easier

2.Paramedian

when there is narrowing of the

interspace or difficulty in flexion of

the spine

Paramedian Approach:

Larger Aperture

Better feel


28/117

28

Epidural anesthesia

Epidural anesthesia technique Preparation of the skin is done in a circular motion

from the center out to the periphery

Use all 3 scrub brushes

Place eye drape centered over your target You can use either the end of your pen or your

fingernail to make an indentation in the back to find

your target more readily


29/117

29

Epidural Anesthesia

Epidural anesthesia technique Skin wheal is accomplished with plain lidocaine

Be fairly generous

Seeker needle is placed and more local injected on

removal Some people like to use an 18g needle to break the

skin, followed by the epidural needle into the same

hole

This is because the epidural needle is not sharp andsignificant pressure may be required to break the skin

with it


30/117

30

Epidural Anesthesia

Epidural anesthesia technique The needle is inserted using landmarks and position

identical to that used in spinal anesthesia

Advance the needle and go through the supraspinous

ligament (feels gritty) and seat it in the intraspinousligament

Now the needle should not droop when you let go

Remove the stylet at that time and place your glass

syringe tightly onto the hub of the needle


31/117

31

Epidural anesthesia


32/117

32

Epidural Anesthesia

Epidural anesthesia technique Loss of resistance technique

Some people use saline

Some use air

Some wet the barrel with saline and use air Some use a combination of air and saline

Advance the needle 1mm at a time, then ballot the

syringe


33/117

33

Epidural Anesthesia

Epidural anesthesia technique Loss of resistance technique

Maintain contact with the skin with your nondominanthand

You will notice the resistance increase when you enter

the ligamentum flavum This is not always the case in OB

Continue to advance until air/saline injects with ease

Injecting saline may help tent the dura and makecatheter placement easier

If fluid rushes back at you when you disconnect thesyringe, it is probably CSF


34/117

34

Epidural Technique(Loss of Resistance Technique)

Hand-position

Note depth

Air or Saline debate

Catheter 3-5 cm in space (should go easily)


35/117

35

Air vs Saline LOR Technique


36/117

36

Hanging drop technique

Consider forCervicalEpidurals (thinepidural

space) Prone or

sitting


37/117

37

Epidural anesthesia


38/117

38

Epidural Anesthesia

Epidural anesthesia technique If you think you may have wet tapped the patient, butare not sure, or if you aspirate fluid from your catheter,you can test it using glucose test strips

The catheter has a large mark on it to signify the end

of the needle You advance the catheter 2.5 to 4cm

Hold the catheter as you remove the needle

When the catheter is visible at the skin, grasp it there

and pull the needle the rest of the way off


39/117

39

Epidural Anesthesia

Epidural anesthesia technique Place the catheter injection adapter onto the catheter

Push the end of the catheter into the adapter and

screw it closed

Give it a gentle tug to ensure it is seated and clamped Tape the catheter in the manner. The techniques

vary greatly


40/117

40

Epidural Anesthesia

Epidural anesthesia technique Using sterile technique, draw up your test dose

Aspirate the catheter to ensure you do not see fluid or

blood

Inject 3ml of test dose (pt.should be on the monitor) If catheter is intravenous, you should notice a 20%

increase in B/P and Heart rate, due to the 15ug

epinephrine

If the catheter is subarachnoid, you should notice a

sympathectomy and partial sensory/motor block ensure


41/117

41


42/117

42

Epidural Anesthesia

Epidural anesthesia technique The rule of thumb is 0.5-1.5ml of local per segment

of block desired

3-5ml of local every 3 minutes until level desired is

reached Slow dosing decreases the untoward sympathectomy

complications

Baricity is not a factorin the epidural space,

because there is no other fluid normally present


43/117

43

Epidural anesthesia


44/117

44

Epidural anesthesia


45/117

45

Epidural Anesthesia

Epidural anesthesia technique Place the patient in the position of comfort if laboring

For non labor patients, do not position them for

surgery until you are sure you have an adequate

block Gravity matters! It will influence the direction and

spread of the block, so consider its implications

during your dosing regimen


46/117

46

Epidural anesthesia


47/117

47

Epidural Anesthesia

Combined spinal/epidural technique Spinal anesthetic followed by epidural infusion

Combines rapid onset with sustained analgesia

May be used for surgery/post op pain management

May be used for labor/delivery

Access epidural space

Spinal needle fits through the lumen of the epidural

Epidural needle is special must have back eye


48/117

48

Epidural anesthesia

Undocumented concern

exists that some of the

epidural injection canmigrate subarachnoid,

causing an increased

level of block


49/117

49

Epidural Anesthesia

Immediate complications of epidurals Sympathetic nervous system disruption

(sympathectomy)

Severe hypotension (pre-ganglionic sympathetic block)

Peripheral vasodilation Venous pooling

Reduction in venous return

High block may result in anesthetizing cardiac

accelerators (T1-T4), with resulting slowed heartrate

called the Bainbridge Reflex


50/117

50

Epidural Anesthesia

Immediate complications of epidurals Perioperative hypotension

Rapid position changes

Skeletal muscle tone loss

Decreased venous return Reflex surgical stimulation

Low volume status

Preoperative medications

Concurrent medical problems


51/117

51

Epidural Anesthesia

Immediate complications of epidurals Perioperative management of hypotension

Non glucose containing crystalloid solutions

5mL/kg bolus

Elevated heart rate phenylephrine (if no

contraindications)

Decreased heart rate ephedrine (if no

contraindications)

Risk of mortality increases the longer hypotension

persists

Be careful using trendelenburg position, especially

when you are using a hyperbaric spinal or high volume

epidural

E id l A h i


52/117

52

Epidural Anesthesia

Immediate complications of epidurals Hypertension

Rare, but does happen

Anxiety

Pain Vasopressors

Consider vasodilators, narcotics, anxioulytics

Always consider discomfort in the places that are NOT

anesthetized.

E id l A th i


53/117

53

Epidural Anesthesia

Immediate complications of epidurals Hypoxia and/or hypercarbia

High level of block can be insidious

Remember C3,4,5 keeps the diaphragm alive

Once your level of blockead has exceeded C3, phrenicnerve paralysis will ensue

Perception of intercostal nerves and abdominal

excursion is lost at the level of T2-4

Intercostal nerves account for 20% of tidal breathing

some of our patients dont tolerate that well!

E id l A th i


54/117

54

Epidural Anesthesia

Immediate complications of epidurals Hypoxia and/or hypercarbia

Anxiety due to inability to sense tidal breathing may

occur

Increased doses of sedatives and/or narcotics cancompound your problem

Hypoventilation increases with decreasing level of

consciousness

With intercostal nerve paralysis, cough becomes

ineffective

May lead to inability to protect the airway

E id l A th i


55/117

55

Epidural Anesthesia

Total spinal/epidural Can lead to acute pulmonary collapse Treated symptomatically

Intubation required

Will loose consciousness Will be severely hypotensive, requiring vasopressor

infusion

Unopposed parasympathetic system leads tobradycardia and vomiting

E id l A th i


56/117

56

Epidural Anesthesia

Immediate complications of epidurals Nausea and/or vomiting

Parasympathetically mediated

Always rule out neurological hypoxia as the first cause

Factors that increase neurological hypoxia: ETOH (ethyl alcohol )

Obesity

Prone position

Apprehension

High level of blockade

E id l A th i


57/117

57

Epidural Anesthesia

Immediate complications of epidurals Intravascular injection

You can neverover test dose a catheter

You should re-test dose if it has been 4 hours since

placement or last bolus IV lidocaine leads to neurologic symptoms, such as

ringing in the ears, metallic taste in mouth, numbness

and/or tingling around the mouth

Epinephrine 15ug should be enough to cause

hypertension, palpitations, anxiety, tachycardia

E id l A th i


58/117

58

Epidural Anesthesia

Immediate complications of epidurals Intravascular injection

ALWAYS aspirate your catheter before you inject

EVERY time

Positive blood aspiration requires immediate removaland/or replacement of catheter

Positive CSF aspiration is problematic- use blood

glucose strip to test if unsure, or CSF will precipitate

when mixed with thiopental (not as accurate)

E id l A th i


59/117

59

Epidural Anesthesia

Immediate complications of epidurals Subarachnoid injection

Immediate change in sensorium

Anxiety

Dyspnea Immediate intubation and vasopressor support are

crucial to survival

Discontinue the catheter

Call for help!

E id l A th i


60/117

60

Epidural Anesthesia

Delayed complications of epidurals Post dural puncture headache (PDPH)

Can occur after either obvious or occult dural puncture

CSF leaks chronically out of the hole in the dura

Decreased amount of available CSF in Subarachnoidspace

Medulla and brainstem sag into foramen magnum

Resulting stretching of the meninges and pulling on the

tentorium cause the headache

E id l A th i


61/117

61

Epidural Anesthesia


Headaches most common in parturients, as they

already have a decreased CSF production and

engorged epidural veins

The proposed causes are related to

Needle type and size

Direction of the bevel

Number of punctures

Patient position

Epid ral Anesthesia


62/117

62

Epidural Anesthesia


Incidence decreases with age

More common in women than men

Patient expectations have been correlated with

incidence

Symptoms include:

Increased pain with upright position

Frontal/occipital headache

Stiff neck and shoulders

Nausea and/or vomiting

Vertigo( )

Blurred vision

Epidural anesthesia


63/117

63

Epidural anesthesia

Epidural Anesthesia


64/117

64

Epidural Anesthesia


Conservative treatment is always attempted first

Bed rest

Vigorous hydration (if tolerated) Use of sedatives and opioids

Abdominal binder for ambulation

Caffeine and niacin

Epidural Anesthesia


65/117

65

Epidural Anesthesia


Definitive treatment is epidural blood patch

Epidural space is accessed using sterile technique

30cc of blood drawn from dependent antecubital ofpatient

Blood is slowly injected into epidural needle until the

patient complains of pressure in the back

Pt. Placed supine flat in bed for 2 hours

Severe backache (you artificially induced one heck of abruise!) almost always follows (tx with ice, analgesics)

Epidural Anesthesia


66/117

66

Epidural Anesthesia

Delayed complications of epidurals Low back pain

Many patients will complain of backache after epiduralremoved

Traumatic procedure with large needle

Consider if patient positioning during surgery couldhave exacerbated symptoms

Were there multiple attempts/punctures?

Prolonged labor?

Epidural Anesthesia


67/117

67

Epidural Anesthesia

Delayed complications of epidurals Urinary retention

Common in labor

Most places place foley after epidural in place

Sympathetic blockade allows for parasympatheticoverride

Bladder distention may occur with fluid bolus

Full bladder can impede fetal decent

Narcotics can exacerbate urinary retention Allow attempt to void, if possible

Epidural Anesthesia


68/117

68

Epidural Anesthesia

Delayed complications of epidurals Infection Septic meningitis

Aseptic meningitis

Adhesive arachnoiditis Intraneural injection

Injection of wrong medications

Undiagnosed neurological disease

Epidural Anesthesia


69/117

69

Epidural Anesthesia

Technical difficulties in epidurals Broken needles

Most common cause is burying the needle

Broken or sheared catheters

NEVER pull a catheter back through the insertion needle

ALWAYS chart that the tip of the catheter was intact whenyou removed it

Visually inspect all catheters before inserting them

Glass from broken vials in the epidural space

Break away from the tray and use a 4X4

Use filter needles Do not core the bottom of the vial when drawing from it


70/117

70


71/117

71


72/117

72


73/117

73


74/117

74


75/117

75


76/117

76


77/117

77


78/117

78


79/117

79


80/117

80


81/117

81


82/117

82


83/117

83


84/117

84


85/117

85


86/117

86

Section 2 Spinal anesthesia


87/117

87

Spinal anesthesiainvolves the administration of local anesthetic into

the subarachnoid space.

Anatomy


88/117

88

y

1.The spinal canal extends from the foramen magnumto the sacral hiatus.

2.Three interlaminar ligaments bind the vertebral

processes together:

supraspinous ligamentinterspinous ligament

ligamentum flavum

3. The spinal cord extends the length of the vertebral canal

during fetal life, ends at about L-3 at birth, and moves

progressively cephalad to reach the adult position near

L-1 by 2 years of age.

Anatomy


89/117

89

4. The spinal cord is invested in three meninges:

The pia mater.

The dura mater.

The arachnoid .

5. The subarachnoid space lies between the pia

mater and the arachnoid and extends from the

attachment of the dura at S-2 to the cerebralventricles above. The space contains the spinal

cord, nerves, cerebrospinal fluid (CSF), and

blood vessels that supply the cord.

y

Physiology


90/117

90

Physiology

1.Neural blockade. Smaller C fibers conveying autonomicimpulses are more easily blocked than the larger sensory

and motor fibers.

2. Cardiovascular. Hypotension is directly proportional to

the degree ofsympathetic blockade produced.3. Respiratory. Low spinal anesthesia has no effect on

ventilation. With ascending height of the block into the

thoracic area, there is a progressive ascending intercostal

muscle paralysis.

Physiology


91/117

91

4.Visceral effects

Bladder.

Intestine.

5. Renal blood flow is maintained, except

with severe hypotension.

6. Neuroendocrine.

7. Thermoregulation.

y gy

Technique


92/117

92

q

1.Spinal needle.

Technique


93/117

93

2.Patient position.

q

a.lateral position .

b.sitting position

c.prone position

Technique


94/117

94

3.Procedure

a.The L2-3, L3-4, or L4-5 interspaces are commonly

used for spinal anesthesia.

b. Disinfect a large area of skin with an appropriate

antiseptic solution.

c. Check the stylet for correct fit within the needle.

d. Raise a skin wheal with 1% lidocaine and a 25-gauge

needle at the spinal puncture site.

q

Technique


95/117

95

e. Approaches1.Midline.

2.Paramedian.

3.Needle placement.

5.Administration of anesthetic.

4.Remove the stylet

Technique


96/117

96

f. Closely monitor (every 60 to 90 seconds)

blood pressure, pulse, and respiratory function

for 10 to 15 minutes. Determine the ascending

anesthetic level by noting the response to gentlepinprick or a cold alcohol swab. Stabilization

of the local anesthetic level takes about 20 minutes.

Determinants of level of spinal blockade


97/117

97

p

1.Drug dose.

2. Drug volume.

3. Turbulence of CSF.

4. Baricity of local anesthetic solution.5. Increased intraabdominal pressure.

6. Spinal curvatures.

Complications


98/117

98

p

1.Hypotension

2. Bradycardia3. Paresthesias.

4. Bloody tap.

5. Dyspnea

6. Apnea7. Nausea and vomiting

8. Postdural puncture headache

9. Backache.

10. Urinary retention.

11. Neurologic impairment

12. Infection


99/117

99

Epidural techniques are more difficult to master,

so knowledge of where your needle is is vital

Summary


100/117

100

Midline Approach

-Skin

-Subcutaneous tissue

-Supraspinous ligament

-Interspinous ligament- Ligamentum flavum

-Epidural space

- Dura mater

-Arachnoid materParamedian or Lateral Approach

-Same as midline excluding supraspinous

& interspinous ligaments


101/117

101

Section 3 Caudal anesthesia (Learn by yourself)

References(video)


102/117

102

http://v.blog.sohu.com/u/vw/318279




( )
http://v.blog.sohu.com/u/vw/318279http://v.blog.sohu.com/u/vw/289724http://v.blog.sohu.com/u/vw/877237http://v.blog.sohu.com/u/vw/1627820http://v.blog.sohu.com/u/vw/1627820http://v.blog.sohu.com/u/vw/877237http://v.blog.sohu.com/u/vw/289724http://v.blog.sohu.com/u/vw/318279


103/117

Peripheral nervesare classified according to size and function


104/117

104


105/117

105

a. Sympathetic block with peripheral vasodilation

and skin temperature elevation.

b. Loss of pain and temperature sensation.c. Loss of proprioception.

d. Loss of touch and pressure sensation.

e. Motor paralysis.

Neural blockade of peripheral nerves

usually progresses in the following order:

Pathophysiologic factors


106/117

106

p y g

a. A decrease in cardiac outputreduces the volume of distribution and plasma clearance

of local anesthetics, increasing plasma concentration and

the potential for toxicity.

b. Severe hepatic diseasemay prolong the durationof action of amino amides.

c.Renal diseasehas minimal effect.d. Patients withreduced cholinesterase activity

(newborns and pregnant patients) and patients withatypical

cholinesterasemay have an increased potential for toxicity.

e.Fetal acidosismay result in greater transplacental transferand trapping of local anesthetics from mother to her fetus and

thus may have an increased potential for fetal toxicity.

Spine Landmarks/Positions

(Fetal Sitting Prone)


107/117

107

(Fetal, Sitting, Prone)


108/117

108

Sitting Position

Advantages:Advantages:

Ease of placementEase of placement

Disadvantages:Disadvantages:

VasovagalVasovagalOnset w/ hypo orOnset w/ hypo or

hyperbarichyperbaric

SedationSedation


109/117

109

Landmarks

L1 End of cordL1 End of cord

S2 End of duraS2 End of dura


110/117

110


111/117

111

Reverse Trendelenburg Position


112/117

112

steep Trendelenburg position


113/117

113


114/117

114


115/117

115


116/117

116


117/117

Local Anesthetics 5

Documents

Transcript of Local Anesthetics 5