1 Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc. Anesthetic...

1Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc.

Anesthetic Induction

Patient loses consciousness and enters surgical anesthesia Take the patient from consciousness to stage III

anesthesia smoothly and rapidly Intubate when possible while animal is still light IV induction is most common and takes animals

through the excitement stage most rapidly Attempt to avoid the excitement/struggling stage,

which is seen more often with mask induction IM induction results in smooth, gradual CNS

depression with little apparent time spent in the excitement stage


IV Induction

Drugs used Mixture of equal volumes of ketamine and

diazepam or midazolam Propofol Neuroleptanalgesics Thiopental sodium Etomidate Various other combinations containing

dissociatives, tranquilizers, and opioids


IV Induction (Cont’d)

Administer IV to effect (unconsciousness) Don’t administer the entire calculated dose all at

once Allow for individual patient response to anesthetic


IV Induction (Cont’d)

Premedication drugs can affect the dose of general anesthetic required

Titration IV drugs given as a series of bolus injections and

discontinued when desired effect is reached IV induction produces up to 10-20 minutes of

anesthesia If more time is needed, anesthesia is maintained

with inhalation anesthetics or administration of propofol, methohexital, or etomidate by repeat boluses or CRI


Inhalation Induction

Anesthetic induction using a facemask or induction chamber

Drugs used: isoflurane and sevoflurane Low blood-gas solubility coefficient Results in rapid passage through stage II

anesthesia


Inhalation Induction (Cont’d)

Mask induction Use of a facemask to induce anesthesia Requires skillful restraint to prevent patient or

operator injury Don’t restrict chest excursions or the airway Fit the mask prior to induction Mask obscures muzzle and eyes normally used for

monitoring Need higher oxygen flow rates than with

endotracheal tube


Inhalation Induction: Facemask

Cautions Exposes personnel to waste anesthetic gas

• Need adequate room ventilation Patient struggling can lead to epinephrine release

• Use only on calm or sedated patients Longer induction period

• Avoid in patients with poor respiratory function Intubate immediately when possible

• To gain control of airway and ventilation Always keep airway open

• Don’t occlude nostrils or compress airway or chest


Inhalation Induction: Chamber

Placing patient in a closed chamber infused with anesthetic gas Patient is usually <5-7 kg body weight Used for small, aggressive patients

Examine chamber prior to use Tight-fitting lid with two gas ports


Inhalation Induction: Chamber (Cont’d)

Complications Stress, trauma, vomiting, airway blockage Hard to monitor patient Exposes personnel to waste anesthetic gas

• Attach scavenger Epinephrine release

• Predisposes patient to cardiac arrhythmias and hypotension


IM Induction

Neuroleptanalgesic combinations and a variety of combinations of tranquilizers, dissociatives, and opioids used to induce general anesthesia

Benefits Use in animals in which IV injections are difficult

• Young animals, aggressive animals, wild animals, captive animals in zoos

May need restraint equipment, blowpipe, or tranquilizing gun


IM Induction vs. IV Induction

The dose of a drug needed for IM induction is generally about twice the corresponding IV dose

IM induction takes longer to achieve high enough brain concentration to induce anesthesia

After peak effect of the IM drug is reached and the patient is still too light, an additional drug or inhalant agent must be administered to get the patient deep enough to intubate

IM induction results in a longer recovery period because of a longer metabolism time


Endotracheal Intubation

Endotracheal tube is placed in the patient’s airway after general anesthesia induction Conducts air or anesthetic gases directly from oral

cavity to trachea Bypasses the nasal passages and pharynx Can be connected to an anesthetic machine to

maintain anesthesia


Endotracheal Intubation (Cont’d)

Benefits Helps maintain an open airway

• Leave in place until the swallowing reflex returns More efficient delivery of anesthetic gas than

facemask• Decreased exposure of personnel to waste gas

With inflated cuff helps prevent aspiration of vomitus, blood, saliva

Reduces anatomic dead space• Improved efficiency of gas exchange

Ventilation can be supported manually or mechanically

• Especially useful for patients in cardiac or respiratory arrest


Feline Intubation


Equipment for Endotracheal Intubation

Three endotracheal tubes of slightly different diameters

Two-foot length of IV tubing or rolled gauze to secure tube

Gauze sponge to grasp tongue 12-mL syringe to inflate cuff Good light source Stylette for narrow diameter tubes Lidocaine injectable solution or gel to control

laryngospasm (cats) Laryngoscope with appropriate blade


Intubation Equipment


Selecting an Endotracheal Tube

Diameter Small enough to not cause trachea injury Large enough to provide a seal with inflated cuff

Length: minimize mechanical dead space Must reach the thoracic inlet Must not extend beyond the end of the muzzle

Patient Species, conformation, and breed

Preparation


Proper Endotracheal Tube Placement


Intubation Procedure

Know the anatomy of the throat Pharynx and larynx

Know the proper restraint and positioning techniques Don’t attempt intubation unless you can visualize

the larynx Have proper lighting Induce patient with IV anesthetic

Unconsciousness, no voluntary movement, no pedal reflex, sufficient muscle relaxation, no swallowing when tongue is pulled


Anatomy of the Pharynx


Intubation Procedure

Insert tube rapidly and correctly Place patient in lateral recumbency

Secure the tube and inflate the cuff Turn on the oxygen Attach the breathing circuit Turn on the anesthetic vaporizer Begin patient monitoring


Endotracheal Intubation in Small Animals


Checking for Proper Tube Placement

Revisualize larynx and confirm the tube is in the correct location

Watch reservoir bag as animal breathes Feel for air movement from the tube connector as

patient exhales Fogging of the tube during exhalation Unidirectional valve motion Palpate the neck Ability of patient to vocalize indicates misplaced tube Patient coughs during intubation Capnometer connection


Laryngospasm

Reflex closure of the glottis in response to contact with an object or substance Common in cats, swine, and small ruminants in

light plane of anesthesia Makes intubation very difficult; larynx is easily

damaged May lead to cyanosis or hypoxemia


Laryngospasm (Cont’d)

Prevention 2% injectable lidocaine or lidocaine gel Adequate depth of anesthesia Wait for glottis to open before intubating Don’t force the tube


Securing the Tube and Cuff Inflation

Tie the ET tube securely without compressing the tube

Cuff the tube Extend the patient’s head Have an assistant close the pop-off valve and

compress the reservoir bag Listen for gas leaks Inflate the cuff until the leaking just ceases at a

pressure of 20 cm H2O


Complications of Intubation

Vagus nerve stimulation- _________________ Brachycephalic dogs or other breed deformities-

____________ Overzealous intubation efforts-

_____________________ Overinflation of cuff- __________________ Obstructed endotracheal tube_________________ Waiting too long to remove the tube____________ Improper cleaning and sanitizing between

uses_________________Mrs. Singers big no no!! Tracheal and/or laryngeal irritation-______________


Maintenance of General Anesthesia

Inhalant agent Repeated boluses of ultrashort-acting agents Continuous rate infusion (CRI) Injectable and inhalant agents Intramuscular injections


Patient Positioning, Comfort, and Safety

Support the patient as it loses consciousness (especially the head)

Remove IV needle and syringe immediately after successful intubation

Lay patient in lateral recumbency immediately after intubation; then secure the tube and inflate the cuff

Ensure the endotracheal tube is inserted properly without bends or kinks


Patient Positioning, Comfort, and Safety (Cont’d)

Temporarily disconnect tube when turning the patient

Support anesthetic machine hoses so no drag is put on the endotracheal tube

Check position of hoses and tube during transfer and repositioning

Make sure reservoir bag is visible at all times Put animals in as normal a position as

possible on the surgery table


Patient Positioning, Comfort, and Safety (Cont’d)

Don’t use heavy drapes or instruments that will lie on the chest of small animals

Don’t overtighten leg restraints Place patient on a heat-retaining surface Place normal lung up if one lung is diseased Be cautious of tilting the surgery table Use artificial tears or other corneal lubricant


Anesthetic Recovery

The period between the time the anesthetic is discontinued and the time the patient is able to stand and walk without assistance

Influencing factors Length of anesthetic period Condition of patient Type of anesthetic administered and route of

administration Patient body temperature Patient breed


The Anesthetist’s Role in Recovery

Discontinue administration of anesthetic agents

Continually to monitor patient through the stages of recovery

Administer oxygen as necessary, especially to shivering patients Oxygen source placed close to the nostrils Elizabethan collar and cellophane cover Nasal catheter Oxygen cage

Administer reversal agents if available


The Anesthetist’s Role in Recovery (Cont’d)

Maintain patent airway and extubate when appropriate Prepare by deflating cuff and untying gauze Remove when the swallowing reflex returns (dogs,

cats) or when signs of impending arousal are present (voluntary limb, tail, or head movements)

Remove the tube in one slow, steady motion



Provide general nursing care Quiet handling, calm reassurance, attention to

patient comfort level Prior to consciousness remove all restraint ties

and make sure all accessory procedures are complete

Prior to consciousness remove all monitoring equipment, probes, cuffs, and electrodes

Be gentle when moving the patient Leave IV catheter in place until recovery is

complete



Provide general nursing care (Cont’d) Hasten recovery with gentle stimulation

(talking, rubbing, gently move ET tube) Turn every 10-15 minutes to prevent hypostatic

congestion Never leave patient unattended Gradually rewarm hypothermic patients



Provide adequate analgesia and other prescribed medications Analgesics should be administered before the

onset of pain Adequate analgesia

• Patient sleeps comfortably with minimal signs of discomfort

Dose adjustment or switching to a different analgesic may be necessary to control pain

Prepare patient for ongoing hospital care or prepare patient for release

1 Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc. Anesthetic...

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Transcript of 1 Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc. Anesthetic...