General Anesthetics

Question 1

Halothane

Answer 1

inhaled anesthetic
most blood-soluble (inc. size of blood compartment), therefore slowest onset of action
other tissue compartments produce a steeper decline in the concentration gradient from lung to brain, causing delayed onset of anesthesia
hepatotoxicity (halothane hepatitis)
bronchodilating properties
respiratory depressants

Question 2

desflurane

Answer 2

inhaled anesthetic
less blood-soluble
partial pressure quickly equilibrates through blood and brain compartments to reach anesthetizing concentrations
airway irritation 
bronchodilating properties
respiratory depressants

Question 3

enflurane

Answer 3

inhaled anesthetic
nephrotoxicity
bronchodilating properties
respiratory depressants

Question 4

sevoflurane

Answer 4

inhaled anesthetic
nephrotoxicity
bronchodilating properties
respiratory depressants

Question 5

nitrous oxide

Answer 5

inhaled anesthetic
depress cardiac function in concentration-dependent manner
bronchodilating properties
only inhaled anesthetic that doesn’t cause a dose-dependent decrease in tidal volume and increase in respiratory rate

Question 6

isoflurane

Answer 6

inhaled anesthetic
airway irritation
bronchodilating properties
respiratory depressants

Question 7

propofol: MOA, pharmacokinetics

Answer 7

• IV anesthetic
• lipophilic - rapid onset (as are other IV anesthetics)
• most frequently administered drug for induction of anesthesia, also good for maintenance of anesthesia b/c pharmacokinetics allow for continuous infusion

presumed MOA:
potentiation of chloride current mediated through GABA-A receptor complex

pharmacokinetics:
-rapidly metabolized by liver, also extrahepatic metabolism in lungs

• recovery more complete, less “hangover” than thiopental -likely due to high plasma clearance
• termination of drug after single bolus dose = result of redistribution from highly perfused (brain) to less-well-perfused (skeletal muscle) compartments
• context-sensitive half-time is brief, even after prolonged infusion

Question 8

propofol: effectos

Answer 8

CNS:

• hypnotic, not analgesic
• general suppression of CNS activity
• dec. cerebral blood flow and cerebral metabolic rate (dec. ICP and intraocular pressure)
• dec. cerebral perfusion pressure

Cardiovascular:
-dec. systemic BP (more than other drugs) b/c profound vasodilation in arterial and venous circulation and inhibition of baroreceptor response

Respiratory:

• potent respiratory depressant
• produces apnea after induction dose
• ventilatory response to hypoxia and hypercapnia reduced

other:
- antiemetic activity
- pain on injection is common!

Question 9

barbiturates: thiopental, methohexital: MOA, pharmacokinetics

Answer 9

• largely been replaced in induction by propofol
• combo of enhancing inhibitory and inhibiting excitatory neurotransmission

pharmacokinetics:
- hepatic metabolism
- thiopental = metabolized more slowly, long elimination half-time
- recovery after single bolus dose= comparable for thiopental and methohexital (depends on redistribution to inactive tissue sites rather than on metabolism)

Question 10

barbituates: effects

Answer 10

CNS:

• dose-dependent CNS depression (ranging from sedation to general anesthesia when administered as bolus injection
• do not produce analgesia, may reduce pain threshold –> hyperalgesia
• potent cerebral vasoconstrictors, produce decreases in cerebral blood flow, cerebral blood volume, ICP

Cardio:

• dec. systemic BP (b/c peripheral vasodilation)
• minimal inhibition of baroreceptor reflex

Respiratory:
-resp. depressants, typically produce transient apnea

clinical induction of anesthesia, usually occurs in less than 30 sec.

Question 11

benzodiazapines: midzolam, lorazepam, diazepam

Answer 11

left off here b/c tired -slide 37