Lecture 5 - Injectable Anesthetics I

Injectable

Which category of anesthetics are indicated for sedation, induction of anesthesia, maintenance (TIVA/PIVA), intermittent bolusing, CRI, and seizure management? They produce dose-dependent CNS depression, have a short onset, and the average duration of action is short but effects will end gradually.

No

Do injectable anesthetics produce any environmental pollution?

No

After administering injectable anesthetics, can the drug be retrieved?

Preoxygenation

What is the term for giving an animal oxygen prior to intubation or induction of anesthesia?

HR, RR, MM

Which three things (abbreviated), should be checked on the patient before induction of anesthesia?

Induction

What is the term for the administration of drugs until the patient becomes unconscious and allows endotracheal intubation?

Barbiturates

Which group of injectable anesthetics come as either thio- or oxy- varieties and include thiopentol and pentobarbitol, among others?

Thiopentol

Which injectable anesthetic is the only main example of a thiobarbiturate that is commonly used? It has a rapid onset of action (20-30s), is highly protein bound, has a duration of 5-10m, induces the CYP450 enzyme during hepatic metabolism, does renal excretion, and enhances the GABAA receptor. It can only be given through IV injection due to tissue necrosis occurring. It is not water-soluble at neutral pH, is a yellow powder, is reconstituted with water, remains stable for 7 days, and when turbid will have lost its activity.

Oxybarbiturates

Which group of barbiturates includes pentobarbitol, phenobarbitol, and methohexitol?

Thiobarbiturates

Which group of barbiturates includes thiopentol?

CYP450

Which hepatic enzyme is induced by thiopentol during metabolism of that drug?

GABA A

Which receptor is enhanced by the action of Thiopental?

IV

Which route is the only one which thiopental can be given as it otherwise will cause tissue necrosis? It is given for induction in CV stable patients, helps with fast endotracheal intubation, is used in patients with increased ICP, and is bolussed when the horse is at a superficial level.

Turbid

If a solution of Thiopental is what, it will have lost its activity?

No

Is thiopental analgesic?

Yes

Does thiopental cause respiratory depression, apnea, bronchoconstriction, hypotension, decreased CO, vasodilation, arrythmias, and cross the placenta?

Greyhounds

Which dog breed lack an enzyme to metabolize thiopental, in addition to having minimal fat tissue, resulting in that drug remaining longer periods in the brain? Thiopental should be used with caution in this breed.

Pentobarbital

Which oxybarbiturate has a long duration of action except in sheep and goats?

Propofol

Which non-barbiturate injectable anesthetic is lipid soluble, has rapid onset, rapid distribution, binds to protein and RBCs, has an onset of 60-90m and duration of 10-15m, undergoes glucuronidation into non-active metabolites in the liver and is excreted by the kidneys? Extra-hepatic metabolism has been shown to occur in cats in the pulmonary tissue. It enhances GABA A receptors and inhibits NMDA receptors.

NMDA

While propofol enhances GABA A receptors, it inhibits what receptors?

No

While propofol causes vasodilation, a negative inotropic effect, and decrease in CO, does it cause an increase in HR?

Depression

Does propofol cause respiratory and CNS depression or induction?

No

Is propofol an analgesic?

No

Is propofol a good choice of anesthetic for hemodynamically compromised patients?

No

Does propofol cause any changes in hepatic blood flow or GFR?

Appetite stimulant, Antiemetic

What two effects does propofol have on the GI tract?

Propofol myoclonus

What condition can be seen when giving propofol in which there are muscle jerks alongside muscle relaxation?

Yes

Does propofol cross the placenta and allow for use in C-sections?

Benzyl alcohol

Propofol added with what allows glucuronidation metabolism and is available for use in dogs, but can cause neurologic signs? This additive allows longer use of open containers. This formulation should never be used for TIVA and is also called PropoVet multidose and Propoflo28.

Cat

Which species has reduced capacity for glucuronidation, meaning that recovery from propofol will be longer than in other animals, and repeated use of it will result in anorexia, depression, diarrhea, facial edema, and delayed recovery? It should not be used for CRI in these animals and their Hb is also prone to oxidative injury by phenolic compounds in the drug, leading to decreased PCV and heinz body anemia.

Yes

Is propofol indicated for c-sections, renal patients, hepatic patients, and TIVA (dogs only)?

Yes

Can propofol cause hypovolemia/shock, heart failure, and diabetic hyperlipidemia/pancreatitis?

Etomidate

Which injectable anesthetic is the best choice for heart patients? It is a short-acting hypnotic, is formulated with intra-lipid emulsion, and agonizes the GABA A receptor. Its duration is 5-10 minutes. It has a large volume of distribution, fast onset, 75% is protein-bound, and is metabolized by hydrolysis by hepatic enzymes and plasma esterases.

GABA A

Which receptor is enhanced/agonized by etomidate?

Minimal

Is the respiratory depression caused by etomidate minimal or maximal? Dose-dependent apnea is reported after injection and a reduction in tidal volume is also seen which is compensated by increased RR.

Muscle relaxation

Use of etomidate is usually combined with benzodiazepines or fentanyl prior to administration as what activity of these drugs will help to mitigate myoclonus, dystonia, and tremors caused by the etomidate?

No

Is etomidate indicated for critically ill patients? Adrenocortical suppression is known to occur 6 hours after bolus in dogs and 5 hours after bolus in cats. It is not indicated for patients with adrenocortical disease or stress and corticoids may need to be administered if using high doses.

Yes

While etomidate causes CNS depression, decreased CMRO2, decreased ICP, and decreased CBF, does it maintain cerebral perfusion? It is also associated with tonic-clonic seizures and should be avoided in epileptic patients.

No

Should etomidate be used in epileptic patients?

No

Is etomidate an analgesic?

Alfaxalone

Which drug is an important steroid anesthetic, is a neuroactive steroid, is used in dogs, cats, rabbits, and wildlife, and is given IM? It is a colorless solution, does not irritate tissues, does not promote bacterial growth, and may precipitate with benzodiazepines. It is a GABA receptor agonist.

GABA

On which receptor is Alfaxalone an agonist?

Multidose

Which formulation of alfaxalone has a shelf life of 28 days and is used in dogs and cats?

Multidose IDX

Which formulation of Alfaxalone has a shelf life of 56 days, and is only used in minor species like reptiles, fish, birds, etc.?

Yes

Can alfaxalone be given SC, IM, or IV? It is a good alternative for sick or aggressive cats, does not have significant protein binding, undergoes hepatic metabolism, and is eliminated in the bile, urine, and feces. It is short acting (10 minutes) and has smooth induction but longer onset (60 seconds).

Less

Does Alfaxalone have more or less CVS effects than propofol? It causes respiratory depression and apnea, decreased cerebral blood flow/ICP/CMRO, and increased heart rate, decreased CO, and hypotension.

Cat

Alfaxalone can cause myoclonus and opisthotonus in what species during recovery? It is suitable for CRI in this species and repeat doses are not associated with heinz body anemia.

Alfaxalone

Does alfaxalone or propofol have a longer and poorer quality recovery time?

No

Is alfaxalone an analgesic? It is indicated for IM sedation, fractious dogs with heart disease, deep feline sedation, induction in SA and swine, slow titration to effect can be done to minimize respiratory depression and CVS effects, and in C-sections and TIVA. It is contraindicated in hypovolemia/shock, heart failure, and large volume IM.

Yes

Is use of alfaxalone without premedication associated with bad recoveries?

TIVA

What is the acronym for total intravenous anesthesia? It refers to using only IV drugs and not inhalant anesthetics during anesthesia to reduce post-op side effects.

PIVA

What is the acronym for partial intravenous anesthesia? This refers to combining inhalant and IV anesthetics.