Induction and Inhaled Anesthetics

What causes a pharmacologically induced and reversible state of coma through alteration of neurotransmission at multiple CNS sites?

general anesthesia

What are the 5 requirements for anesthetics?

unconsciousness

amnesia

analgesia

muscle relaxation

cardiopulmonary stability

What is the principle inhibitor neurotransmitter?

GABA

What is the principle excitatory neurotransmitter?

glutamate

What receptors does glutamate ligand to?

NMDAr

What are the two targets for induction anesthetic drugs?

GABA agonist

NMDA antagonist

What is an example of an NMDA antagonist drug?

Ketamine

What is an example of a GABA agonist?

propofol

alfaxalone

etomidate

How do general anesthetics make it to the brain so quickly?

the circle of Willis

What is used as clinical markers for stages/depth of general anesthesia?

GUEDEL classification

Which GABA agonist was discovered in the vet field, is not a controlled substance, has a rapid recovery, and rapid induction of unconsciousness?

propofol

How is propofol administered and why?

IV because it has poor water solubility and a short half-life

Can Propofol provide analgesia?

no

What CV effects does Propofol have?

dose-dependent vasodilation

reduced cardiac contractility depending on dose

What respiratory effects does propofol have?

Causes respiratory depression depending on the dose

Which general anesthetic was withdrawn from human and vet markets due to anaphylactoid reactions shortly after entering in the markets in the 1970s?

alfaxalone

How is the new alfaxalone in the vet field different?

given in a solution with a beta-cyclodextrin

Why is the new alfaxalone not FDA approved?

bone marrow suppression seen in a very few cases of non-human primates

How is alfaxalone administered?

IV, IM, SC administration

How does alfaxalone compare to propofol in relation to CV and respiratory effects?

alfaxolone does not suppress HR and BP

Is etomidate controlled?

no

What is the best agent when no derangement of CV system is desired?

etomidate

Why is etomidate not always used?

inhibits cortisol production

no analgesia

VERY poor water solubility

Is Ketamine controlled?

Yes, schedule III

Ketamine has a pH of ~3, what does that mean when giving it IM?

It is going to burn upon injection

Which general anesthetic is commonly used in wildlife and zoo immoblizations?

ketamine

How is Ketamine administered?

IV or IM

SC

What sort of neurological effects does Ketamine have?

amnesia

out of body experience

What best describes the pharmacodynamics of ketamine?

2- compartment model: rapid redistribution in 2-5 minutes and then elimination is more prolonged for 1-2 hours

What is the active metabolite of ketamine?

Norketamine (1/3 the activity)

How is ketamine eliminated?

renally

What would you expect when giving ketamine to a patient with renal failure?

prolonged effects of the drug

What CV effects does ketamine have?

increased cardiac output, increased heart rate,

Does ketamine provide analgesia?

yes, more towards pain management

What was the first inhaled anesthetic used in the history of medicine?

nitrous oxide

Is nitrous oxide still used in a hospital setting today? How?

yes, used often for procedural sedation

What is the mechanism of action for nitrous oxide?

NMDA antagonist