VASG Anesthetic Induction Protocols

	Veterinary Anesthesia & Analgesia Support Group
	Practical Information for the Compassionate Veterinary Practitioner

HOME

Anesthetic Induction Protocols

1) Alfaxalone - coming soon

a) In the mean time see our alfaxalone review

2) Etomidate

a) General Description

i) An imidazole

b) Patient selection

i) Recommended use

(1) Patients with serious cardiac that include a decrease in contractility, such as cardiomyopathy patients.

ii) Cautionary information

(1) May cause myoclonus, retching, or excitement during induction or recovery

(a) Adequate preanesthetic sedation will minimize or eliminate this

(2) Suppresses adrenocortical function for up to 3 hours following administration

(a) This effect can be overcome by the administration of a short acting corticosteroid if there is an existing concern

(b) It has been reported that this lack of a “stress response” may actually reduce patient morbidity

(3) The Abbott etomidate product contains propylene glycol which may cause hemolysis

(a) Hemolysis may create a pigment load that can be significant for renal compromised patients

(i) Give slowly IV or give with IV fluids to minimize pain on injection and/or hemolysis

(b) Note: Diazepam is also in a propylene glycol solution

(4) The European Braun product, etomidate-lipuro, is the same concentration as the Abbott product but the vehicle is a hyperlipid emulsion like propofol. There is no risk of hemolysis with this product but once opened, the product should be handled appropriately and used within 8 hours.

c) Dosage

i) Routine induction

(1) Dogs

(a) 0.5 to 3.0 mg/kg (0.25 to 1.5 mg/lb) IV

(2) Cats

(a) 0.5 to 2.5 mg/kg (0.25 to 1.0 mg/lb) IV

(3) If the patient is not adequately sedate, precede the etomidate with diazepam 0.2 to 0.6 mg/kg (0.1 to 0.3 mg/lb) IV

ii) When utilizing the propylene glycol preparation, give slowly IV or give with IV fluids to minimize pain on injection and to minimize hemolysis (both due to the propylene glycol).

d) General Cost Category

i) Very high

3) Diazepam & a pure mu agonist Opioid

a) General Description

i) A benzodiazepine and fentanyl, hydromorphone, methadone, morphine, or oxymorphone

b) Patient selection

i) Recommended use

(1) Debilitated patients

(2) Geriatric patients

(3) Severe valvular insufficiency or cardiomyopathy

ii) Cautionary information

(1) Watch for bradycardia and respiratory depression due to the opioid

(a) Heart rate may decrease but blood pressures are usually adequate.

(2) Opioids, particularly oxymorphone, can create a hypersensitivity to loud noises

(3) This protocol is most effective when the patient is either depressed from their disease or very sedate from the premedications

c) Dosage

i) Routine induction

(1) Dogs

(a) Diazepam 0.4 mg/kg (0.2 mg/lb) IV followed by

(b) One of the following opioids:

(i) Hydromorphone 0.1 mg/kg (0.05 mg/lb) IV

(ii) Oxymorphone 0.05 mg/kg (0.025 mg/lb) IV

(iii) Fentanyl 0.005 mg/kg (0.0025 mg/lb) IV

(iv) Morphine 0.2 mg/kg (0.1 mg/lb) IV slowly

(c) Some patients will require a second dose of diazepam and some patients will require a second dose of the narcotic, given in that order, to complete the induction

(d) Rarely, patients will require a third dose of diazepam followed by a third dose of the narcotic, if needed, to complete the induction

(e) If, at any point, the canine patient is nearly, but not quite, able to be intubated, the addition of 2 mg/kg (1 mg/lb) lidocaine IV, may deepen the anesthetic effect and facilitate successful intubation

(i) This strategy is useful when minimizing the induction agent for more critical patients

(2) Cats –the doses are the same as for the dog, cats are often difficult to intubate with benzodiazepine/opioid combinations alone

(i) A small ketamine 2 to 10 mg/kg (1 to 5 mg/lb) or propofol 0.5 to 2.0 mg/kg(0.25 to 1.0 mg/lb) bolus may be necessary to complete induction and intubation.

(ii) Cats are more sensitive to the toxic effects of lidocaine (CNS stimulation, seizures). Lidocaine is not recommended for use in cats at this time.

ii) In dogs, surgical anesthesia can often be maintained using additional opioid with a benzodiazepine

(1) Hydromorphone 0.04 mg/kg (0.02 mg/lb) or oxymorphone 0.02 mg/kg (0.01 mg/lb) every 20 to 30 minutes and diazepam 0.1 mg/kg (0.05 mg/lb) every 40 to 60 minutes

(a) Maintenance of anesthesia by this method may be indicated if isoflurane or sevoflurane anesthesia is not well tolerated (i.e. adequate blood pressure is difficult to maintain)

(b) This technique is not often not as successful in cats though a significantly lower their inhalant concentration necessary to maintain surgical anesthesia

(2) CRIs of mu agonists, especially fentanyl, with midazolam can be used to accomplish this same strategy. See Maintenance Protocols for more information on this method

d) General Cost Category

i) Low to moderately high if oxymorphone is used)

4) Ketamine & Diazepam

a) General Description

i) Combination of a benzodiazepine & a dissociative agent

b) Patient selection

i) Recommended use

(1) Animals of any age in generally good health

(2) An acceptable choice for animals with well compensated valvular heart disease

(3) Acceptable for sighthounds

ii) Cautionary information

(1) Avoid if:

(a) Intracranial disease is suspected (can raise ICP)

(b) An increase in intraoccular pressure is contraindicated (i.e. descmetocele)

(d) Serious cardiac disease (uncompensated mitral or tricuspid regurgitation or moderate to severe cardiomyopathies)

c) Dosage

i) Routine induction

(1) Dog & Cat

(a) Diazepam – 0.25 mg/kg (0.125 mg/lb)

(b) Ketamine – 5 mg/kg (2. 5 mg/lb)

i) Routes of administration

(1) IV

(a) While these two drugs can be mixed together in the same syringe it is preferable to administer all of the diazepam first, then titrate the ketamine to final desired effect

(2) IM/SC use, while not specifically contraindicated, is not recommended as IM diazepam is painful and not absorbed well

d) General Cost Category

i) Low – currently the least expensive of the induction agents

5) Ketamine & Midazolam

a) General Description

i) Combination of a benzodiazepine & a dissociative agent

ii) Similar to Ketamine & Diazepam

b) Patient selection

i) Recommended use

(1) Animals of any age in generally good health

(2) An acceptable choice for animals with well compensated valvular heart disease

(3) Acceptable for sighthounds

(4) Older difficult-to-handle cats where IM administration is required to gain control of the patient

(a) Follow with IV catheter and finish induction with IV agent(s)

(b) Midazolam’s IM absorption is excellent

ii) Cautionary information

(1) Avoid if:

(a) Intracranial disease is suspected (raises ICP)

(b) An increase in intraoccular pressure is contraindicated (i.e. descmetocele)

(d) Serious cardiac disease (uncompensated mitral or tricuspid regurgitation or moderate to severe cardiomyopathies)

(2) Etomidate should considered our first choice for serious cardiac disease, especially cardiomyopathies

c) Dosage

i) Routine induction

(1) Dog & Cat

(a) Midazolam – 0.25 mg/kg (0.125 mg/lb)

(b) Ketamine – 5 mg/kg (2. 5 mg/lb)

i) Routes of administration

(1) IV preferred

(a) While these two drugs can be mixed together in the same syringe it is preferable to administer the midazolam first, then titrate the ketamine to final desired effect

(1) IM use a consideration if patient is too fractious to allow IV catheterization

(a) These two drugs can be mixed together in same syringe

d) General Cost Category

i) Moderately low

6) Propofol

a) General Description

i) Propofol is an alkylphenol derivative suspended in a hyperlipid emulsion

b) Patient selection

i) Recommended use

(1) Animals of any age

(2) Cases in which rapid recovery is desired

(3) Diabetes Mellitus

(a) Propofol is capable of providing a smooth and rapid return to a comfortable state if premedications are appropriately utilized

(b) Appetite appears increased in many patients for a short period of time after recovery from propofol

(4) Outpatient procedures

(5) Sighthounds

(6) Giant breed dogs when early ambulation is desired

ii) Cautionary information

(1) Hyperlipid emulsion and no preservative promote bacterial growth

(a) Once opened, nonpreservative product should be used within 6 to 12 hours

c) Dosage

i) Routine induction

(1) Dogs

(a) 4 to 6 mg/kg (2 - 3 mg/lb) if not depressed or sedate

(i) Effective premeds or pre-existing CNS depression or debilitation can reduce the dose required for intubation to 1 to 4 mg/kg (0.5 to 2 mg/lb)

(2) Cats

(a) 6 to 8 mg/kg (3 - 4 mg/lb) if not depressed or sedate

(i) Effective premeds or pre-existing CNS depression or debilitation can reduce the dose required for intubation to 1 to 4 mg/kg (0.5 to 2 mg/lb) or less

ii) Plan on delivering the calculated dose over 90-120 seconds, stopping when the patient appears deep enough to intubate

(1) Rapid administration causes:

(a) Apnea of short duration

(b) Hypotension

iii) If, at any point, the canine patient is nearly, but not quite, able to be intubated, the addition of 2 mg/kg (1 mg/lb) lidocaine IV, may deepen the anesthetic effect and facilitate successful intubation

(1) This strategy is useful when minimizing the induction agent for more critical patients

(2) Cats are more sensitive to the toxic effects of lidocaine (CNS stimulation, seizures). IV Lidocaine, at this dose, is not recommended for use in cats at this time.

iv) Routes of administration

(1) IV only

(2) Intraosseous

d) General Cost Category

i) Moderate

7) Sevoflurane/Isoflurane Mask Induction

a) General Description

i) Low solubility inhalant agents

b) Patient selection

i) Recommended use

(1) Mask inductions are not recommended for most patient groups

ii) Cautionary information

(a) Increased patient stress

(i) Increased arrhythmic risk

(b) Unnecessary staff exposure to anesthetic agents

(d) Prolonged period of unsecured airway with an increased risk of airway compromise or obstruction

(e) High concentrations of inhalant agents are required to achieve mask induction. Higher doses produce more cardiovascular and respiratory depression than seen with comparable doses of IV induction agents.

(i) During intubation removal of the mask results in cessation of drug administration of the drug and recovery from anesthesia begins as the drug is eliminated.

(ii) Once intubated higher concentrations of inhalant are required compared to use of IV induction drugs.

(f) Contraindicated in brachycephalic patients

c) Dosage

i) Isoflurane 1 to 5 %

(1) Mask Induction

(a) Start with 100% oxygen at 3 liters/min for 3 - 5 minutes if patient is tolerant of the face mask

(i) Do not cover patients eyes

(b) After 3 - 5 minutes of O2, start isoflurane @ 0.5 %

(d) Then increase to 3.5 % - 5 % to complete induction

ii) Sevoflurane 2 to 7 %

(2) Mask Induction

(a) Start with 100% oxygen at 3 liters/min for 3 - 5 minutes if patient is tolerant of the face mask

(i) Do not cover patients eyes

(b) After 3 - 5 minutes of O2, start sevoflurane at 1 %

(d) Then increase to 5 % - 7 % to complete induction

d) General Cost Category

i) Moderately high with Sevoflurane

8) Thiopental

a) General Description

i) Ultra-short acting thiobarbiturate

b) Patient selection

i) General use

(1) Healthy animals in the Good to Excellent category

ii) Cautionary information

(1) Avoid if:

(a) Sighthound (lower volume of distribution and altered metabolism)

(b) Anemic

(i) Thiopental can cause splenic pooling of RBCs leading to a rapid decrease in PCV of up to 30%

(2) Extravascular thiopental may produce tissue necrosis

(a) Infiltrate area with saline, 0.5 to 1 mg of dexamethasone and 1 mg/kg (0.5 mg/lb) of lidocaine

(b) Additionally, a gauze soaked in DMSO can be wrapped over the site

c) Dosage

i) Routine induction

(1) Dog

(a) Begin with 12 mg/kg (6 mg/lb)

(i) Administer 4 to 6 mg/kg (2 - 3 mg/lb) rapid bolus initially followed by additional small boluses to effect

1. Excessively slow injection may precipitate unwanted excitement

(2) Cat

(a) Same as dog

(3) If at any point the canine patient is nearly, but not quite, able to be intubated, the addition of 2 mg/kg (1 mg/lb) lidocaine IV, may deepen the anesthetic effect and facilitate successful intubation

(a) ) This strategy is useful when minimizing the induction agent for more critical patients

(b) Cats are more sensitive to the toxic effects of lidocaine (CNS stimulation, seizures). Lidocaine is not recommended for use in cats at this time.

(4) Route of administration

(a) IV only

d) General Cost Category

i) Moderate

9) Tiletamine & Zolazepam (Telazol)

a) General Description

i) 50/50 mixture of a benzodiazepine & a dissociative agent

b) Patient selection

i) General use

(1) Healthy animals in the Good to Excellent category

(2) An appropriate for sighthounds

ii) Cautionary information

(a) See Ketamine & Diazepam

c) Dosage

i) Routine induction

(1) Dog

(a) Unsedated – 2 mg/kg (1 mg/lb) IV bolus

(b) Sedated or pre-existing CNS depression or debilitation - draw up 2 mg/kg (1 mg/lb), give 25 - 50% as bolus then additional increments to effect

(2) Vicious, aggressive dogs

(a) 5 mg/kg (2.5 mg/lb) IM - usually reach lateral recumbancy within 10 minutes

(b) May be combined with acepromazine for more dramatic effect

(3) Cats

(a) Same as dog

ii) Routes of administration

(1) IV/IM/SC

(a) IV – allows for lower Telazol doses

(b) IM – more rapid effect than SC but more painful

d) General Cost Category

i) Moderately low

Return to top of page