Induction and Maintenance Drugs

Question 1

Induction

Answer 1

Moving from conscious to unconscious state
IV injectable agents (some IM)

Question 2

Co-induction agents

Answer 2

Benzodiazepines (midazolam + ketamine, midaz + propofol, midaz + alfaxalone)
Ketofol (etamine + propofol)
Ketafax (ketamine + alfaxalone)
Lidocaine
Opioids

Question 3

MOA for induction drugs

Answer 3

Enhances GABA (inhibitory NT) at the GABAa receptor

Question 4

Induction agents

Answer 4

Barbituates
Dissociatives
Propofol
Etomidate
Alfaxalone
Opioid induction

Question 5

Dissociatives

Answer 5

Ketamine and Tiletamine

Question 6

Dissociatives MOA

Answer 6

NMDA receptor antagonist → change of awareness, catalepsy, amnesia and analgesia

Question 7

Effects of Dissociatives

Answer 7

↑ CBF, ICP and IOP
Myocardial depression and ↑ HR, BP and CO
Palpebral and corneal reflexes intact
Central eye position

Question 8

Dissociatives precautions

Answer 8

Never use ketamine alone for induction
Apneustic breathing
Hypersalivation (don’t use anticholinergics)
Emergence delirium

Question 9

What does ketamine alone cause?

Answer 9

Muscle and limb rigidity
Induce seizures → CNS stimulation
combine with benzodiazepine

Question 10

Dissociative contraindications

Answer 10

Depleted catecholamines (shock, trauma, stress)
Glaucoma, corneal ulcer with ↑ IOP
CV compromise, etc.

Question 11

Propofol/ Propofol- 28 effects

Answer 11

↓ CBF, ICP and CMRO2 (head trauma, brain lesions)
Extra-hepatic metabolism in dogs (renal and hepatic dz)
Propofol only for boluses or CRI

Question 12

T/F: Cats have ↓ ability to metabolize propofol

Answer 12

TRUE
don’t use for more than 3 consecutive days or use CRI

Question 13

Precautions for Propofol/ Propofol- 28

Answer 13

Respiratory depression → apnea
Myclonus (too slow without premedication)- seizure like
↓ contractility and SVR → hypotension
Prolonged recovery in cats → liver dz

Question 14

Etomidate effects

Answer 14

Good for uncompensated CV dz
↓ CBF, ICP and CMRO2 (neuro brain disorders)
Resp. depression (slight)

Question 15

Etomidate precautions

Answer 15

Expensive
Myoclonus, excitement, retching if used by itself
Suppresses adrenocortical function (3-6 hrs)
Pain and hemolysis if give too fast IV

Question 16

Alfaxalone

Answer 16

Neuro-active steroid anesthetic
Class 4 controlled
Multidose dogs and cats, IDX minor species

Question 17

Effects of Alfaxalone

Answer 17

Smooth, rapid induction and m. relaxation
IV induction and maintenance

Question 18

Alfaxalone precautions

Answer 18

Emergence delirium on recovery when used alone
No analgesia

Question 19

Opioid induction

Answer 19

Benzodiazepine + short acting opioid
Used for Hemodynamically unstable and critically ill patients (ASA 4 or 5)

Question 20

Opioid induction precautions

Answer 20

Slower induction
Intubation and O2 support mandatory
Hypersensitive to noise, light and stimulation

Question 21

Maintenance phase

Answer 21

Inhalants
Injectable agents IM or IV
Total intravenous anesthesia (TIVA)

Question 22

Inhalans

Answer 22

Isoflurane (cheapest)
Sevoflurane
Halothane
Desflurane
all will cause dose dependent CV and resp. depression

Question 23

Inhalant physical properties

Answer 23

Vapor pressure
Solubility
Minimum alveolar concentration (MAC)

Question 24

Vapor pressure

Answer 24

Ability to evaporate
↑ pressure = easy to evaporate

Question 25

Solubility

Answer 25

Inhalant vapor dissolved within a solvent
Sevo by itself = quicker induction and recovery than iso

Question 26

Inhalants move along __________ not concentration gradients

Answer 26

Partial pressure gradients

Question 27

Partial pressure gradients

Answer 27

Inspired air → alveolar air → blood → brain
Soluble= slow, insoluble= fast

Question 28

Minimum alveolar concentration (MAC)

Answer 28

% inhalant that prevents purposeful movement in 50% of patients exposed to a noxious stimulus
lower MAC, more potent the inhalant

Question 29

Sevo is _______ potent than iso, so it requires _______ vaporizer setting to maintain

Answer 29

Less
Higher

Question 30

Maintenance with induction agents

Answer 30

Ketamine
Tiletamine/zolazapm
Alfaxalone

Question 31

Maintenance with induction agents risk

Answer 31

↑ risk to hypoventilation, airwat obstruction and hypoxemia
No assist in ventilation
Depth difficult to control
Resp. arrest

Question 32

TIVA

Answer 32

Propofol or alfaxalone CRI + opioid CRI

Question 33

TIVA uses

Answer 33

Craniotomies with ↑ ICP
Critically ill patients → hypotension with inhalants
Patients long term ventilation in ICU
Patients with uncoltrolled seizure acitvity
Sx procedures or bronchoscopy of upper airway

Question 34

Precaution with TIVA

Answer 34

Intubation and 100% O2 support is mandatory
Hypoventilation → controlled ventilation