Clinical Anesthetics

Question 1

goals of general anesthesia

Answer 1

analgesia, amnesia, unconsciousness, suppression of responses to surgery (stress, motor, CV, pain)

Question 2

drugs for analgesia

Answer 2

isoflurane, morphine

Question 3

drugs for amnesia

Answer 3

midazolam, isoflurane

Question 4

drugs for unconsciousness

Answer 4

propofol, isoflurane

Question 5

drugs for suppression of responses

Answer 5

cis-atracurium muscle relaxant (neostigmine + glycopyrrolate), fentanyl, isoflurane, phenytoin (seizures), dexamethasone, hydralazine, labetalol, ondansetron, morphine

Question 6

rationale for using multiple drugs

Answer 6

maximize benefit, minimize problems (use IV and inhaled together)

Question 7

example of a drug that could have been used for amnesia, analgesia, unconsciousness, muscle relaxation; why it isn’t used?

Answer 7

sevoflurane

slow induction, severe CV depression, cerebral vasodilation, prolonged emergence, inadequate post op pain control

Question 8

what about drug interactions?

Answer 8

reduced doses minimize side effects, and balanced anesthesia techniques rely on interactions

Question 9

explain how the effects of drug interactions are “additive”

Answer 9

effect of drug combo is expected based on SUM of doses; 1/2 ED + 1/2 ED= 1 ED

Question 10

explain how the effects of drug interactions are “synergistic”

Answer 10

effect of 1 drug is enhanced by another, so the combined effect is greater than expected based on the sum of the doses; 1/2 ED + 1/2 ED > 1 ED

Question 11

examples of beneficial drug interactions

Answer 11

benzodiazepines/opioids; midazolam/propofol for preop sedation/induction; combos of inhaled agents; inhaled agent and muscle relaxant; labetalol/hydralazine; treatment of N/V

Question 12

pharmacokinetic interaction of midazolam and fentanyl

Answer 12

competitive inhibition of CYP3A4 by fentanyl, altering midazolam clearance at high doses

Question 13

describe the 2nd gas effect

Answer 13

uptake of 1st gas reduces lung volume, increases conc of 2nd gas/ increases uptake of 2nd gas

Question 14

using an inhaled agent with NMBD (neuromuscular blocking drug) allows…

Answer 14

lower dose of NMBD antagonists

Question 15

all NMBDs increase blockade by..

Answer 15

decreased prejunctional ACh release

decreased postjunctional sensitivity to ACh

Question 16

describe the benefits of combining labetalol and hydralazine

Answer 16

labetalol (anti HTN, reduces HR and a stimulation (constriction))

adding hydralazine (vasodilator) decreases bp without increasing heart rate

Question 17

the multiple receptors in CTZ (chemoreceptor trigger zone) and vomiting center than can be blocked

Answer 17

5HT, DA, ACh, histamine, opioid

Question 18

an effective combo for N/V

Answer 18

5HT and DA blockers together: ondansetron and droperidol

5HT blockers + steroids is most effective combo for N/V relief

Question 19

examples of detrimental interaction

Answer 19

etomidate/succinylcholine

phenytoin/cis-atracurium

ephedrine esp with cocaine, methamphetamine

Question 20

why is etomidate/succinylcholine a detrimental interaction?

Answer 20

pH differences, can result in a precipitate

Question 21

why is phenytoin/cis-atracurium a detrimental interaction?

Answer 21

antagonism of any non-depolarizing NMBD

Question 22

what type of drug is ephedrine?

Answer 22

vasopressor; direct and indirect sympathomimetic

Question 23

what does ephedrine have significant drug interactions with?

Answer 23

MAOIs, meth, cocaine