90B: Intravenous + Inhaled Anesthetics

Question 1

What is the MOA for benzodiazpenes?

Answer 1

• Benzodiazepines are used for sedation prior to surgery
o facilitate binding of GABA to GABA-A receptors to increase frequency of receptor activation

causes increased Cl- conductance intracellularly - drops resting membrane potential to even more negative range - harder to fire action potential - sedation/sleep

Question 2

What is the MOA for barbiturates?

Answer 2

• Barbiturates induce a state of unconsciousness for general anesthesia during surgery
o facilitates binding of GABA to GABA-A receptors to increase duration of receptor activation - increases Cl- conductance

Question 3

What is the MOA of propofol? Why is it so commonly used?

Answer 3

• Propofol induces a state of general anesthesia or a partial state (sedation)
o is a GABA receptor agonist
o is popular b/c has a very low half-life as infusion duration continues — only takes 15 mins after surgery and stopping infusion to wake the person up
o is also an antiemetic (which is another reason why it is so popular b/c a lot of other anesthetics cause nausea)

Question 4

Why are all anesthetics dangerous?

Answer 4

• all anesthetics are dangerous because they can cause respiratory depression
o GABA mediated CL- conductance - neuronal hyperpolarization - decreased responsiveness of the ventilatory pacemaker cells in the pons to CO2 - respiratory acidosis + hypercapnia - hypoxemia (b/c an increased pCO2 will decrease PAO2)
• anesthetics are also concerning for HYPOTENSION

Question 5

Explain how certain anesthetics are concerning for causing hypotension.

Answer 5

o	Thiopental (barbiturates) decrease cardiac output and central venous pressure -  decrease in BP
o	Propofol decreases systemic vascular resistance (b/c it is a vasodilator) - causes hypotension

Question 6

Describe the effects of anesthetics on cerebral metabolic rate of O2 consumption and cerebral blood flow.

Answer 6

• IV anesthetics w/ decrease cerebral metabolic rate of O2 consumption (CMRO2)
o w/ also decrease cerebral blood flow (CBF) b/c it sees that O2 consumption has decreased so it doesn’t need that much blood flow anymore

Question 7

What is etomidate used for and what are its advantages/disadvantages?

Answer 7

• Etomidate is used to induce rapid general anesthesia; is a GABA receptor agonist
o advantages – maintains hemodynamic stability (BP doesn’t change too much)
o disadvantages – adrenocortical suppression, nausea, pain on injection, and myoclonus

Question 8

What is ketamine used for? What are its advantages/disadvantages?

Answer 8

• Ketamine is used in small doses w/ other anesthetics; antagonizes the excitatory NMDA receptor
o advantages – hemodynamic stability, analgesia, and minimal respiratory depression (won’t become apneic like propofol)
o disadvantages – HTN/tachycardia, increased CMRO2 + CBF + ICP, hypersalivation, and psychosis/delirium (unpleasant for patients)

Question 9

What are volatile agents?

what are their effects on CMRO2 and CBF?

Answer 9

• Volatile agents (halothane, isoflurane, sevoflurane, desflurane) are easy to use and reliable
o not sure of mechanism of action but believed to involve the lipid expansion effect
o decreases CMRO2 but increases CBF b/c they severely vasodilate blood vessels — increased ICP
o Side effects: respiratory depression, bronchodilation, decreased mucociliary clearance, bronchospasm, myocardial depression, decreased SVR b/c of peripheral vasodilation