Induction and Maintenance Drugs Flashcards
Induction
Moving from conscious to unconscious state
IV injectable agents (some IM)
Co-induction agents
Benzodiazepines (midazolam + ketamine, midaz + propofol, midaz + alfaxalone)
Ketofol (etamine + propofol)
Ketafax (ketamine + alfaxalone)
Lidocaine
Opioids
MOA for induction drugs
Enhances GABA (inhibitory NT) at the GABAa receptor
Induction agents
Barbituates
Dissociatives
Propofol
Etomidate
Alfaxalone
Opioid induction
Dissociatives
Ketamine and Tiletamine
Dissociatives MOA
NMDA receptor antagonist → change of awareness, catalepsy, amnesia and analgesia
Effects of Dissociatives
↑ CBF, ICP and IOP
Myocardial depression and ↑ HR, BP and CO
Palpebral and corneal reflexes intact
Central eye position
Dissociatives precautions
Never use ketamine alone for induction
Apneustic breathing
Hypersalivation (don’t use anticholinergics)
Emergence delirium
What does ketamine alone cause?
Muscle and limb rigidity
Induce seizures → CNS stimulation
combine with benzodiazepine
Dissociative contraindications
Depleted catecholamines (shock, trauma, stress)
Glaucoma, corneal ulcer with ↑ IOP
CV compromise, etc.
Propofol/ Propofol- 28 effects
↓ CBF, ICP and CMRO2 (head trauma, brain lesions)
Extra-hepatic metabolism in dogs (renal and hepatic dz)
Propofol only for boluses or CRI
T/F: Cats have ↓ ability to metabolize propofol
TRUE
don’t use for more than 3 consecutive days or use CRI
Precautions for Propofol/ Propofol- 28
Respiratory depression → apnea
Myclonus (too slow without premedication)- seizure like
↓ contractility and SVR → hypotension
Prolonged recovery in cats → liver dz
Etomidate effects
Good for uncompensated CV dz
↓ CBF, ICP and CMRO2 (neuro brain disorders)
Resp. depression (slight)
Etomidate precautions
Expensive
Myoclonus, excitement, retching if used by itself
Suppresses adrenocortical function (3-6 hrs)
Pain and hemolysis if give too fast IV
Alfaxalone
Neuro-active steroid anesthetic
Class 4 controlled
Multidose dogs and cats, IDX minor species
Effects of Alfaxalone
Smooth, rapid induction and m. relaxation
IV induction and maintenance
Alfaxalone precautions
Emergence delirium on recovery when used alone
No analgesia
Opioid induction
Benzodiazepine + short acting opioid
Used for Hemodynamically unstable and critically ill patients (ASA 4 or 5)
Opioid induction precautions
Slower induction
Intubation and O2 support mandatory
Hypersensitive to noise, light and stimulation
Maintenance phase
Inhalants
Injectable agents IM or IV
Total intravenous anesthesia (TIVA)
Inhalans
Isoflurane (cheapest)
Sevoflurane
Halothane
Desflurane
all will cause dose dependent CV and resp. depression
Inhalant physical properties
Vapor pressure
Solubility
Minimum alveolar concentration (MAC)
Vapor pressure
Ability to evaporate
↑ pressure = easy to evaporate
Solubility
Inhalant vapor dissolved within a solvent
Sevo by itself = quicker induction and recovery than iso
Inhalants move along __________ not concentration gradients
Partial pressure gradients
Partial pressure gradients
Inspired air → alveolar air → blood → brain
Soluble= slow, insoluble= fast
Minimum alveolar concentration (MAC)
% inhalant that prevents purposeful movement in 50% of patients exposed to a noxious stimulus
lower MAC, more potent the inhalant
Sevo is _______ potent than iso, so it requires _______ vaporizer setting to maintain
Less
Higher
Maintenance with induction agents
Ketamine
Tiletamine/zolazapm
Alfaxalone
Maintenance with induction agents risk
↑ risk to hypoventilation, airwat obstruction and hypoxemia
No assist in ventilation
Depth difficult to control
Resp. arrest
TIVA
Propofol or alfaxalone CRI + opioid CRI
TIVA uses
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
Precaution with TIVA
Intubation and 100% O2 support is mandatory
Hypoventilation → controlled ventilation
