General Anesthetics

Question 1

what are the uses of general anesthetic?

Answer 1

should only be used for surgery

surgery was rare before the induction of general anesthetics

Question 2

what was used prior to general anesthetics?

Answer 2

ethanol
opiates
partial asphyxia
cerebral concussion

Question 3

what are the characteristics of the ideal anesthetic?

Answer 3

"balance anesthesia"
loss of consciousness
amnesia
analgesia
inhibition of reflexes
muscle relaxation
rapid onset and recovery from amnesia
a pleasant experience of px 
no dangerous side effects such as decreased respiration, hypothermia, nausea and vomiting

Question 4

what is the therapeutic index of inhaled general anesthetics?

Answer 4

2-4

very low= lethal very close to therapeutic

Question 5

mechanism of action of inhaled general anesthetic?

Answer 5

inhibition of neuronal firing (Effect on neurotransmission)
potentiation of inhibitory GABAergic neurons
inhibition of excitatory glutaminergic neurons
cortex is most sensitive than the thalamus

Question 6

what are the factors that influence potency?

Answer 6

in general, the greater the lipid solubility, the more potent the agent

Question 7

what is the MAC?

Answer 7

concentration at which 50% of px are unresponsive
minimal alveolar conc similar to ED50
the lower the MAC, the more potent the drug

Question 8

what is the speed of induction?

Answer 8

related to the solubility of the agent in the blood. the more soluble it is in the blood, the slower the onset

Question 9

what does having a high blood/gas coefficient mean?

Answer 9

more soluble in blood= slower induction

Question 10

what is the speed of recovery?

Answer 10

symmetrical to speed of induction

Question 11

nitrous oxide

Answer 11

gas at room temp
relatively insoluble in blood- stay in gas form- very rapid onset
MAC>100%
rapid induction and recovery
good analgesia
very low potency
no amnesia
not soluble in blood so it tends to leave the blood and enter body cavities as a gas and cause patient discomfort
repeated exposure leads to megaloblastic leukemia, leukopenia

Question 12

what are the halogenated hydrocarbons?

Answer 12

used to maintain anesthesia
can trigger malignant hyperthermia because of the huge increase in calcium uptake by skeletal muscle- stimulate skeletal muscle- causing rigidity, tachycardia, temperature above 107 degree fahrenheit
increase oxygen consumption by muscle

Question 13

which anesthetics are the halogenated hydrocarbons?

Answer 13

isoflurane, desflurane, sevoflurane

increase incidence of liver disease with repeated exposure

Question 14

intravenous general anesthetics

Answer 14

more rapid than inhaled anesthetics

Question 15

methohexitol

Answer 15

a barbiturates
bind to and activate GABAergic neurons- CNS depression
action is terminated by redistribution from the brain

Question 16

propofol

Answer 16

most commonly used parenteral anesthetic
acts to increase GABAergic activity
rapid onset
short duration
anti emetic effect

Question 17

ketamine

Answer 17

analog of phenylcyclidine (angel dust)
dissociative anesthesia- profound amnesia and analgesia
short induction
short duration
binds to a receptor which inhibits glutaminergic neurons
can cause hallucinations in px emerging from anesthesia

Question 18

etomidate

Answer 18

very rapid- nonanalgesic- “conscious sedation”
high therapeutic index
activates GABA receptors
some nausea post op

Question 19

midazolam

Answer 19

benzodiazepine- binds to a benzodiazepine receptor and enhances activity if GABAergic neurons
amnesia