The document discusses anesthetic management in small animals, including general considerations for anesthesia, safe anesthetic practices, pre-anesthetic procedures such as physical examination and intravenous catheter placement, induction and intubation, maintenance of anesthesia, recovery, common anesthetic problems and their treatment, and references for further information. It provides detailed guidelines and recommendations for each step of the anesthetic process in small animals.

1. ANESTHETIC MANAGEMENT
IN SMALL ANIMALS
Dr. Satyajeet Singh

2. General Considerations
 1. breed
 2. temperament
 3. physical/health status
 4. purpose of anesthesia
 5. familiarity with the drugs to be used
 6. any concurrent medication
 7. equipment and available assistance

3. Safe Anesthetic Practices
 1. use of reversible agents whenever
possible
 2. endotracheal intubation should be
mandatory to assure patent airway at all
times
 3. careful monitoring of all anesthetized
patients, including the preanesthetic and
recovery periods
 4. preanesthetic fasting (food 8-12 hours;
water 2-4 hours in small animals), except
in the very small, young or debilitated

4. Pre-Anesthetic
 A. Be sure you are familiar with the physical
status of each patient
 1. obtain complete history and review prior to
anesthesia
 2. perform a thorough physical examination
 3. an accurate weight is important
 particularly in small animals
 adjust for lean body weight
 4. review laboratory data
 determines need for preanesthetic stabilization
 directs drug selection
 directs further preoperative tests

5. Pre-Anesthetic
 B. Formulate specific anesthetic plan
 1. choose a protocol appropriate for the patient
 2. anticipate complications that may arise based on
physical examination and laboratory data, the procedure
being performed, anesthetic drugs used (plan for failure)
 3. calculate doses carefully
 4. draw up drug, label syringes appropriately
 5. prepare anesthetic record

6. Pre-Anesthetic
 C. Place intravenous catheter
 1. aseptic technique
 2. place after premedication, prior to the
induction of anesthesia
 3. exceptions
 intractable animals that must be chemically
immobilized prior to handling
 restraint for catheter placement causes
excessive stress and danger to the patient
 short procedures in healthy patients

7. Pre-Anesthetic
 D. Gather equipment and supplies
 1. Endotracheal tube
 2. Laryngoscope
 3. Preparation of Anesthetic Machine
 4. Assemble monitors
 5. Other Equipment

9. Premedication
 A. Selection is based on:
 1. patient condition
 2. patient temperament
 3. procedure
 4. familiarity with drugs

11. Premedication
 B. Route of Administration
 1. based on temperament
 2. SC, IM, IV all possible routes

14. Premedication
 Dogs
 1. Possible Drugs/Combinations
 Acepromazine + Hydromorphone
 Medetomidine + Hydromorphone
 Midazolam + Hydromorphone
 Hydromorphone (or some other opioid) alone

15. Premedication
 Cats
 1. Possible Drugs/Combinations
 Acepromazine + Hydromorphone (or some other opioid)
 Midazolam + Hydromorphone
 Medetomidine + Hydromorphone
 Medetomidine + Hydromorphone + Ketamine
 Telazol

16. INDUCTION
 A. Intravenous Agents
 a. never inject rapidly
 b. preanesthetics alter the required dose of inhalants,
sometimes profoundly
 c. most induction agents are titrated to effect
 d. adjust induction dose according to the degree of
sedation following premedication

17. Induction
 thiopental
 Propofol
 Thiopental + propofol (1:1)
 diazepam-ketamine
 Telazol
 Neuroleptanalgesic combinations

18. Induction
 Specific Drugs
dose of induction drug can be reduced by administering
lidocaine (1 mg/kg) or diazepam (0.2 mg/kg)
 useful in depressed patients
 Lidocaine helps stabilize myocardium

19. Induction
 Endotracheal Intubation
 be prepared – this should be accomplished quickly (but
don’t panic!!)
 choose a range of tube sizes
 cats: 3.0 – 5.0 mm i.d.
 dogs: 4.0 mm i.d. – 12 mm i.d.
 adequate anesthesia is required prior to intubation
 laryngospasm can occur (especially in cats)

20. Induction
Procedure
 2 people required
 animal in sternal position, lined up along its longitudinal axis
 once appropriate depth of anesthesia has been reached, pull
tongue out of mouth
 use laryngoscope!
 cats
 larynx is sensitive and prone to laryngospasm
 lidocaine spray or 0.1 ml 2% lidocaine will reduce incidence of
laryngospasm
 brachycephalic breeds
 use a laryngoscope
 elongated soft palate may need to be moved dorsally to release the
epiglottis.

24. Checking for proper tube
placement
 1. check for respiratory gas
condensation on the inside of the tube
during inspiration
 2. a correctly placed tube will often
stimulate a cough reflex immediately
following placement
 3. watch for movement of the
rebreathing bag (keeping in mind that
a patient may become apneic
immediately following induction)

25. Checking for proper tube
placement
 4. palpate the neck for two tubes – if
you feel two tubes, you are feeling the
trachea and the endotracheal tube in
the esophagus.
 5. auscultate the chest during assisted
ventilation.
 6. hemoglobin saturation (Pulse
oximetry)
 7. Capnography

26. Maintenance
 General Considerations
 once the patient is at an appropriate level
of anesthesia, turn down vaporizer and
oxygen flow rate to maintenance levels.
 immediately following induction, check
pulse, respiratory rate, pulse quality,
capillary refill time.
 start anesthetic record
 attach monitors
 start fluid administration at an appropriate
rate (5-10 ml/kg/hr)

27. Recovery
 Continue oxygen administration as long as possible after
vaporizer has been turned off
 Deflate cuff and remove tube only when swallowing is
observed
 Watch carefully during recovery.

28. Recovery
 Post-anesthetic monitoring should continue until
the animal can maintain sternal recumbency or
lift its head and until vital signs are stable
 External heat source should be applied to raise
body temperature to within 1 or 2 degrees of
normal body temperature
 Stimulating the animal will speed recovery but
keep in mind that once the stimulation is
stopped that the animal will likely go back to
sleep
 Post-operative analgesics should be
administered as required.

29. Recovery
 Sedation may be required for the animal that
is experiencing a rough recovery
 a. acepromazine
 b. medetomidine
 Fluid therapy should be continued in the
recovery period until the animal is
completely recovered from anesthesia.
Some disease states will require continued
fluid administration.

30. MAINTENANCE OF ANESTHESIA
WITH INJECTABLE AGENTS
 used for short duration procedures or when inhalant
anesthesia is unavailable or contraindicated
 achieved by a single dose for short procedures or small
intermittent boluses doses of a drug or a constant rate
infusion in longer duration procedures

31. MAINTENANCE OF ANESTHESIA
WITH INJECTABLE AGENTS
 Specific drugs or drug combinations:
 1. propofol
 2. ketamine combinations
 3. Ketamine/Alpha 2 Agonist Combinations
 4. Telazol
 5. GXK (Triple drip) in horses/cattle

32. References
 Slatter, D. Textbook of Small Animal
Surgery 3rd
Edition, Volume II, 2003,
Section 17, p. 2503-2623.
 Pain Management for the Surgical Patient
 Patient Monitoring
 Operating Room Emergencies
 Anesthesia and Analgesia for the Trauma
or Shock Patient
 Anesthesia for the Pediatric and Geriatric
Animal

38. Common Anesthetic Problems
 Bradycardia
 Tachycardia
 Hypotension
 Hypertension
 Blood loss
 Apnea
 Tachypnea
 Too Light
 Too Deep

39. Bradycardia
 Remember that a heart rate defined as
bradycardic is specific to a particular
animal/breed. Smaller breeds are
much less tolerant of lower heart rates
while larger breeds don’t have a
problem with a heart rate of 60.
 The target heart rate for an animal
should be its pre-anesthetic heart
rate, keeping in mind that the pre-
anesthetic rate will often be elevated
because of stress/anxiety.

40. Bradycardia
 Possible causes:
 opioid administration
 traction on viscera
 alpha 2 agonist administration
 hypothermia
 dobutamine/dopamine administration
 hypertension
 hypoxemia

41. Bradycardia
 Treatments:
 remove cause (if possible – as in hypothermia)
 anticholinergic
 glycopyrolate 0.005 – 0.02 mg/kg IV
 atropine 0.01 – 0.02 mg/kg IV
 if administering dopamine or dobutamine – discontinue and
wait approximately 5 minutes before administering
anticholinergic

42. Bradycardia
 Atropine – faster onset than glycopyrolate
 don’t be afraid to administer > 1 dose of an
anticholinergic. If the first dose doesn’t work, try a
second or a third. After 3 doses of one anticholinergic,
I will usually administer a dose of the other to see if
that works.

43. Bradycardia
 bradycardia induced by alpha 2 agonists
such as Domitor can be approached this
way:
 if the heart rate is just low, blood pressure
is fine and there are no arrhythmias, then
you don’t really need to treat.
 if arrhythmias do start to appear (second
degree AV block, escape complexes) then it
may be best to administer a small amount of
the reversal (atipamezole) to bring the heart
rate up rather than giving an anticholinergic
(debatable).

44. Bradycardia
bradycardia in response to hypertension is a good
thing. Leave it alone. Correct the hypertension and
the bradycardia will usually go away.

46. Tachycardia
 anticholinergic administration
 hypovolemia
 too light/pain during surgery
 too much dobutamine/dopamine
 hyperthermia
 high ETCO2

47. Tachycardia
 Treatment:
 remove cause
 in animals with high heart rates and normal
blood pressures that are at an appropriate
depth of anesthesia, it is often the case that
they have lower than normal circulating
volume so that the heart has to work
harder/faster to maintain good cardiac output
and blood pressure. Often, the first response
to tachycardia in an animal that is assessed to
be appropriately managed in terms of its
pain, is to administer a fluid bolus (10 ml/kg
crystalloids over 15 min) to see if an increase
in volume will bring the heart rate down.

48. Tachycardia
 high ETCO2 will produce sympathetic
stimulation that can cause an increase
in heart rate. Solution: ventilate
 when an animal is responding to surgical
stimulation, then you should reevaluate
your approach to pain management in
this animal. Often, a supplemental
dose of an opioid (hydromorphone,
fentanyl) will provide you with the
additional analgesia that is required.

49. Hypotension
 Possible Causes:
 hypovolemia/blood loss
 excessive anesthetic dose (usually inhalant but can occur
with injectables such as propofol)
 poor myocardial contractility
 bradycardia (see above)

50. Hypotension
 Treatments:
 generally, the first approach to dealing
with hypotension in an animal under
anesthesia is to a) reduce the dose of
inhalant anesthesia and b) administer a
bolus of either crystalloids (10 ml/kg over
15 min) or dextrans (5 ml/kg initially –
can go up to 20 ml/kg in more emergent
cases) (if non-responsive to a bolus of
crystalloids or you don’t want to give any
more crystalloids.

51. Hypotension
in cases where the inhalant concentration cannot be
lowered but you REALLY need to reduce it because of
cardiovascular depression, you can consider giving a
supplemental dose of narcotic (say hydromorphone =
0.05 – 0.1 mg/kg IV). This will allow you to reduce
the dose of inhalant required for anesthesia.

52. Hypotension
poor contractility can lead to hypotension and can be
the result of cardiovascular depression due to the
inhaled anesthetic or preexisting cardiovascular
disease (i.e. dilated cardiomyopathy). In these cases
administering either dobutamine (3 – 10 ug/kg/min
IV) or dopamine (3-10 ug/kg/min) may be helpful.

55. Hypertension
 Possible Causes:
 too light/inadequate anesthesia
 excessive dobutamine or dopamine administration
 alpha 2 agonist administration
 excessive fluid administration
 elevated ETCO2

56. Hypertension
 Treatments:
 increase depth of anesthesia (either by increasing inhalant
concentration or administering an additional dose of
narcotic)
 reduce dobutamine or dopamine administration
 ventilate if ETCO2 is elevated
 diuresis if volume overload

57. Blood Loss
 Most blood loss during anesthesia occurs
because of a surgical or medical procedure.
Acute blood loss can lead to hypovolemia,
hypotension and reduced oxygen delivery.
Anesthetized animals have greater difficulty
compensating for blood loss than do conscious
animals. Ongoing efforts to quantify blood
loss must be made so that adequate volume
replacement can be made. When quantifying
blood loss, keep in mind that for every 1 ml
of blood lost, you need to give 3 ml of
crystalloids back to restore the volume. This
should be provided in addition to the
calculated maintenance solutions. Animals
that lose 20% of their blood volume should
have that volume replaced with whole blood
rather than crystalloids.

58. Apnea
 can occur at 2 different, distinct time points in the
anesthetic process. 1
 . following induction (particularly with an injectable
anesthetic)
 occurs frequently and will generally resolve on its own
 proceed with intubation, denitrogenating the anesthetic circuit
and lungs (by giving 2-3 good breaths of oxygen once the animal is
connected to the anesthetic machine)
 wait for the animal to redistribute the induction drug to the point
where it begins to respond to carbon dioxide again.

59. Apnea
 In animals where you are particularly concerned about
induction apnea (i.e. animals that already have some
respiratory embarrassment), preoxygenating prior to
the induction of anesthesia will help to reduce the
impact of induction apnea on oxygen levels.

60. Apnea
 May also occur because of being either too deep under
anesthesia (or too light)

61. Tachypnea
 Possible causes:
 too light for the procedure
 excessive ETCO2
 hyperthermia
 hypoxemia
 The most common cause of tachypnea during anesthesia is
an inadequate depth of anesthesia – too light (see below).

62. Tachypnea
 Treatments:
 correct the cause

63. TOO LIGHT
 Possible causes:
 mismatch between the depth of anesthesia (inadequate)
and the level of surgical stimulation (excessive).
 Usually occurs at the beginning of surgery.
 during the transfer of an animal to inhalant anesthesia
following induction with propofol.

64. TOO LIGHT
 Treatments:
 if the animal is moving, then you need to
increase the depth of anesthesia - giving a
supplemental dose of the induction drug is
indicated.
 if you just need to increase the depth
slowly because you have noticed that the
animal is responding a little to surgical
stimulation (i.e. mild increase in blood
pressure, heart rate or respiratory rate),
then you can produce an increase in depth
of anesthesia by a) turning up the
vaporizer and b) increasing the fresh gas
flow rate.

66. TOO DEEP
 Possible Causes:
 mismatch between the depth of anesthesia (excessive) and
the level of surgical stimulation (inadequate.)

67. TOO DEEP
 too much induction drug
 vaporizer set too high.
 Preventing an animal from becoming too
deep under anesthesia requires close
attention to the anesthetic needs of the
animal.
 Before administering an injectable induction
drug, carefully evaluate how sedate the animal
is following the premedication. If it is very
sedate, then you will not have to give much
induction drug.
 In the same vein, if an animal is very deep
after you induce anesthesia, then you will not
have to give much inhalant initially.

68. TOO DEEP
 Treatment:
 if the depth of anesthesia is too deep because of
injectable drugs you can either
 a) reverse part or all of any reversible drugs
 b) support the animal as it metabolizes any non-reversible
drugs.

69. TOO DEEP
 inhaled anesthesia:
 decreasing the vaporizer setting
 increasing the fresh gas flow (this increases the rate at
which the gas containing the reduced concentration
replaces the gas with the “old”, higher concentration of
anesthetic.

70. gpettifer@sympatico.ca

72.  5. The components of an anesthetic machine are listed below.
Choose the order that best describes the flow oxygen through the
machine:
 a) cylinder, pressure gauge, pressure regulator, precision
vaporizer, flow meter, fresh gas outlet/port, breathing circuit,
overflow (pop-off) valve.
 b) pressure regulator, cylinder, pressure gauge, precision
vaporizer, flow meter, fresh gas outlet/port, overflow (pop-off)
valve, breathing circuit
 c) cylinder, pressure gauge, pressure regulator, flow meter,
precision vaporizer, fresh gas outlet/port, overflow (pop-off)
valve, breathing circuit
 d) cylinder, pressure gauge, pressure regulator, flow meter,
precision vaporizer, fresh gas outlet/port, breathing circuit,
overflow (pop-off) valve.
 e) pressure regulator, cylinder, pressure gauge, precision
vaporizer, flow meter, overflow (pop-off) valve, fresh gas port,
breathing circuit

73.  6. All of the following statements concerning
the rebreathing bag are correct except:
 a) it acts as a reservoir bag from which the
animal may breath oxygen and anesthetic gas
 b) it can be used to manually support
ventilation
 c) it allows visual assessment of the respiratory
rate
 d) it traps carbon dioxide expired by the animal
 e) it allows visual assessment of the tidal
volume

74. Physical Exam/Data:
Chest:
Rhythm:
Other:
Labs/Rads/ECG/Other:
Assessment:
ASA Status:
I II III
IV V
PLAN/RECOMMENDATIONS:
FURTHER DIAGNOSTICS:
PRE-ANESTHETIC THERAPY:
PREMEDICATION:
INDUCTION:
MAINTENANCE:
ANALGESIA:
FLUIDS: MONITORING:
PRE-ANESTHETIC EVALUATION FORM
Date: Time:
Patient Name:
Requested By:
History:
PROCEDURE/REASON FOR ANESTHESIA:
=
_________________________________
Glenn Pettifer, DVM, DVSc, DACVA