Anesthesia1- Injectable Anesthetics

induction

• propofol
• alfaxalone
• dissociatives (ketamine, telazol)
• etomidate
• MS-22

it comes as solubilized emulsion of soybean oil, glycerol, and egg lecithin; normal propofol does not have a preservative (PropoFlo28 has an alcohol preservative but not labelled for cats)

[maintain strict aseptic technique and discard open vials at end of day]

• immediate unconsciousness [extremely lipid soluble]
• induction and recovery are rapid and smooth
• duration 5-15 minutes

hepatic and extra-hepatic metabolism

enhances effect of GABA receptors, which are inhibitory--> increased Cl- conduction, resulting in hyperpolarization of postsynaptic neurons

• anesthetic induction
• facilitate long-term restraint (when given as CRI)

potent respiratory depressant: apnea/ severe hypoventilation (depends on dose and speed of administration)

• Normal or increased HR (in response to hypotension)
• Decreased myocardial contractility (dose-dependent)

potent vasodilation, hypotension (short-lived)

• pain/discomfort at injection site
• appetite stimulant
• associated with heinz body formation in cats
• myoclonus

no

has benzyl alcohol as a preservative to increase shelf life, but is not labelled for cats (benzyl alcohol may be toxic to cats)

neuroactive steroid; schedule IV

• immediate unconsciousness, induction and recovery are rapid and smooth (extremely lipid soluble)
• duration approximately 5-20 minutes

hepatic metabolism only! (contrast to propofol)

anesthetic induction as bolus or as a CRI

binds to GABA, which is inhibitory--> modulates neuronal cell membrane Cl- ion transport

at higher doses only, hypoventilation/ apnea

• vasodilation and hypotension
• minimal effects at low doses

• muscle relaxation
• potential for accumulation in cats (unlike propofol)

• ketamine (least potent)
• tiletamine (component of telazol, with zolazepam)
• phencyclidine (most potent)

anesthetic state induced by drugs that interrupt ascending transmission from the unconscious to conscious parts of the brain, characterized by a cataleptoid state and opened eyes

schedule II; schedule III

• Dissociation: acts at the thalamo-neocortical projection system, which limits the ability to interpret sensory input
• Analgesia: NMDA receptor anatgonism

• S ketamine is most potent, more rapid metabolism and recovery, less salivation, and lower incidence of emergence reactions
• BUT it only comes with both, so you're stuck

• redistribution to lean body tissues and fat
• metabolized to norketamine (active metabolite) in the liver then metabolized to inactive metabolite and excreted in urine (dogs)
• in cats, norketamine is excreted in urine

• low doses- combined with sedatives, tranquilizers, and opioids as induction drug
• at high doses (not recommended)- sole anesthetic

increased muscle tone, tremors, occasional seizures, and rough recoveries

• open eyes, maintained palpebral reflexes, dilated pupils (cataleptoid state)
• maintained swallow reflex
• increased cerebral metabolic rate, cerebral blood flow, intraocular pressure, and intracranial pressure (don't use in patient with brain tumor or desmetocele)
• emergence reactions

• [transient, mild, respiratory depression] decreased minute ventilation
• apneustic breathing pattern (inspire--> hold it--> expire a little--> hold it--> expire]
• depressed swallow reflex

• increased HR
• increased CO
• direct myocardial depression (which ONLY manifests during hemodynamic shock)
• increased myocardial oxygen consumption (DO NOT USE IN HCM CATS)
• through direct stimulation of sympathetic NS

wake them up! they are sicker than you think

increase MAP

• good analgesia
• stinging at IM injection site

• less apnea (than propofol alone)
• less hypotension (than propofol alone)
• better muscle relaxation (than ketamine alone)
• fast induction (than ketamine alone)
• lower dose of both drugs

50-50 combination of tiletamine (dissociative) and zolazepam (benzodiazepine)

• redistribution to lean body tissues and fat
• metabolized by the liver

• Dogs- tiletamine lasts longer
• cats- zolazepam lasts longer

• high doses can be used as sole anesthetic (not recommended b/c of different metabolism rates of the 2 drugs and rough recoveries)
• lower doses are usually used in combination with other sedatives, tranquilizers, and opioids for anesthetic induction

• dose-related unconsciousness
• cataleptoid state (open eyes, palpebral reflex, dilated pupils)
• maintained swallow reflex
• [does not have the same cerebral side effects as ketamine but has less research in compromised patients]

• [transient, mild respiratory depression] decreased minute ventilation, apneustic breathing pattern
• swallowing reflex maintained but depressed

• increased HR
• normal or increased CO (usually normal b/c tiletamine inc HR but zolazepam decreases HR)

• increased MAP
• BP transiently decreases then increases

good muscle relaxation d/t zolazepam

• imidazole derivative solubilized in propylene glycol (single isomer R+)
• classified as hypnotic

• penetrates brain rapidly--> rapid but rough induction--> rapid and smooth recovery
• duration is only 5-10 minutes after bolus
• metabolized by the liver

• anesthetic induction agent
• long-term restraint when used as CRI

modulates GABA receptors, enhancing affinity of GABA for GABA receptors--> inhibitory

may decrease tidal volume and increase resp rate, but usually causes minimal resp depression

minimal changes

minimal changes

• pain at injection site
• myoclonus
• retching
• adrenocortical depression (inhibition of conversion of cholesterol to cortisol)

• MS-222 is the fish anesthetic
• water soluble powder used to immobilize fish
• approved for fish intended for consumption with 21 day withdrawal period

light sedation, surgical anesthesia, euthanasia of fish

decreased reaction, loss of opercular activity

loss of equilibrium and locomotion

transfer fish to fresh water w/o drugs