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Anesthetic Induction
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Patient loses consciousness and enters
surgical anesthesia
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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
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IV Induction
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Drugs used
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Mixture of equal volumes of ketamine and
diazepam or midazolam
Propofol
Neuroleptanalgesics
Thiopental sodium
Etomidate
Various other combinations containing
dissociatives, tranquilizers, and opioids
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IV Induction (Cont’d)
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Administer IV to effect (unconsciousness)
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Don’t administer the entire calculated dose all at
once
Allow for individual patient response to anesthetic
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IV Induction (Cont’d)
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Premedication drugs can affect the dose of
general anesthetic required
Titration
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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
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If more time is needed, anesthesia is maintained
with inhalation anesthetics or administration of
propofol, methohexital, or etomidate by repeat
boluses or CRI
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Inhalation Induction
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Anesthetic induction using a facemask or
induction chamber
Drugs used: isoflurane and sevoflurane
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Low blood-gas solubility coefficient
Results in rapid passage through stage II
anesthesia
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Inhalation Induction (Cont’d)
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Mask induction
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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
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Inhalation Induction: Facemask
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Cautions
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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
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Inhalation Induction: Chamber
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Placing patient in a closed chamber infused
with anesthetic gas
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Patient is usually <5-7 kg body weight
Used for small, aggressive patients
Examine chamber prior to use
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Tight-fitting lid with two gas ports
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Inhalation Induction: Chamber
(Cont’d)
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Complications
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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
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IM Induction
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Neuroleptanalgesic combinations and a
variety of combinations of tranquilizers,
dissociatives, and opioids used to induce
general anesthesia
Benefits
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Use in animals in which IV injections are difficult
• Young animals, aggressive animals, wild animals,
captive animals in zoos
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May need restraint equipment, blowpipe, or
tranquilizing gun
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IM Induction vs. IV Induction
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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
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Endotracheal Intubation
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Endotracheal tube is placed in the patient’s
airway after general anesthesia induction
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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
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Endotracheal Intubation (Cont’d)
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Benefits
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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
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Feline Intubation
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Equipment for
Endotracheal Intubation
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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
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Intubation Equipment
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Selecting an Endotracheal Tube
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Diameter
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Length: minimize mechanical dead space
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Must reach the thoracic inlet
Must not extend beyond the end of the muzzle
Patient
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Small enough to not cause trachea injury
Large enough to provide a seal with inflated cuff
Species, conformation, and breed
Preparation
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Proper Endotracheal
Tube Placement
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Intubation Procedure
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Know the anatomy of the throat
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Know the proper restraint and positioning
techniques
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Pharynx and larynx
Don’t attempt intubation unless you can visualize
the larynx
Have proper lighting
Induce patient with IV anesthetic
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Unconsciousness, no voluntary movement, no
pedal reflex, sufficient muscle relaxation, no
swallowing when tongue is pulled
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Anatomy of the Pharynx
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Intubation Procedure
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Insert tube rapidly and correctly
Place patient in lateral recumbency
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Secure the tube and inflate the cuff
Turn on the oxygen
Attach the breathing circuit
Turn on the anesthetic vaporizer
Begin patient monitoring
Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc.
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Endotracheal Intubation
in Small Animals
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Checking for Proper
Tube Placement
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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
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Laryngospasm
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Reflex closure of the glottis in response to
contact with an object or substance
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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
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Laryngospasm (Cont’d)
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Prevention
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2% injectable lidocaine or lidocaine gel
Adequate depth of anesthesia
Wait for glottis to open before intubating
Don’t force the tube
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Securing the Tube and Cuff Inflation
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Tie the ET tube securely without compressing
the tube
Cuff the tube
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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
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Complications of Intubation
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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-______________
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Maintenance of General Anesthesia
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Inhalant agent
Repeated boluses of ultrashort-acting agents
Continuous rate infusion (CRI)
Injectable and inhalant agents
Intramuscular injections
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Patient Positioning, Comfort, and
Safety
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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
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Patient Positioning, Comfort, and
Safety (Cont’d)
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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
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Patient Positioning, Comfort, and
Safety (Cont’d)
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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
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Anesthetic Recovery
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The period between the time the anesthetic is
discontinued and the time the patient is able
to stand and walk without assistance
Influencing factors
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Length of anesthetic period
Condition of patient
Type of anesthetic administered and route of
administration
Patient body temperature
Patient breed
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The Anesthetist’s Role in Recovery
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Discontinue administration of anesthetic
agents
Continually to monitor patient through the
stages of recovery
Administer oxygen as necessary, especially
to shivering patients
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Oxygen source placed close to the nostrils
 Elizabethan collar and cellophane cover
 Nasal catheter
 Oxygen cage
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Administer reversal agents if available
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The Anesthetist’s Role in Recovery
(Cont’d)
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Maintain patent airway and extubate when
appropriate
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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
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The Anesthetist’s Role in Recovery
(Cont’d)
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Provide general nursing care
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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
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The Anesthetist’s Role in Recovery
(Cont’d)
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Provide general nursing care (Cont’d)
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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
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The Anesthetist’s Role in Recovery
(Cont’d)
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Provide adequate analgesia and other
prescribed medications
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Analgesics should be administered before the
onset of pain
Adequate analgesia
• Patient sleeps comfortably with minimal signs of
discomfort
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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
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