general anesthetics

Question 1

What are the uses of GA?

Answer 1

produce unconsciousness and lack of responsiveness to all painful stimuli.
provide conditions for interventions such as surgery to take place.
control physiology during these processes.

Question 2

what constitutes an ideal GA?

Answer 2

unconsciousness, analgesia, muscle relaxation, amnesia, brief & pleasant, depth of anesthesia can be altered easily, minimal ADR, large margin of safety

Question 3

what is an example of combinations which can achieve balanced analgesia

Answer 3

short acting barbiturates, neuromuscular blocking agents, opioids & nitrous oxide

Question 4

general ADR of GA

Answer 4

depression of respiratory & cardiac performance

Question 5

What are some examples of inhalation anesthesia?

Answer 5

volatile liquids: halothane, enflurane, desflurane, isoflurane, sevoflurane
gases: nitrous oxide

Question 6

proposed MOA of inhaled anesthesia

Answer 6

• enhance neurotransmission @ inhibitory synapse through allosterically increasing GABA receptor sensitivity
• depressing neurotransmission @ excitatory synapse by blocking transmission action on NMDA receptor & preventing its activation

Question 7

what is minimum alveolar concentration (MAC)?

Answer 7

• minimum concentration of drug in the alveolar air that will produce immobility in 50% of patients exposed to painful stimulus

Question 8

what is the relation of potency to MAC?

Answer 8

low MAC = high anesthetic potency

Question 9

how to increase absorption of volatile liquids?

Answer 9

• increasing: concentration of GA in inspired air, solubility of GA, blood flow through lungs

Question 10

list some of the toxic metabolites of GA substances

Answer 10

nephrotoxic: inorganic fluorides of isoflurane, sevoflurane & enflurane
hepatotoxic: metabolite of halothane

Question 11

what are some of the ADR of halothane?

Answer 11

• dose dependent respiratory depression
• bradycardia and arrhythmia leading to HoTN & dysrhythmia
• halothane-associated hepatitits

Question 12

when is nitrous oxide used?

Answer 12

analgesia in dentistry and adjunct to supplement analgesic effects of primary anesthetics

Question 13

what is a major concern of nitrous oxide?

Answer 13

post-operative nausea and vomiting

Question 14

what is the advantage of combining IV and inhalation anesthetics?

Answer 14

• allows inhalation dose to be reduced

- produce effects that cannot be achieved with inhalation alone

Question 15

MOA of sodium thiopental (thiopentone)

Answer 15

causes CNS depression by potentiating the action of GABA on GABA receptor gated chloride channel

Question 16

what are some of the advantages of propofol

Answer 16

• ready made in injectable form, no need for reconstitution

- reduced post operative vomiting

Question 17

ADR of propofol

Answer 17

• significant CVD effect during induction (HoTN)

- use with caution in elderly, patients with compromised cardiac function and hypovolemics

Question 18

what is the action of ketamine which results in GA?

Answer 18

dissociative anesthesia

Question 19

ADR of ketamine

Answer 19

unpleasant psychologic reactions may occur during recovery - may be reduced with pre-med of diazepam/midazolam

Question 20

name one advantage of halothane

Answer 20

skeletal muscle relaxant (potentiates other relaxants as well), potent (low MAC)

Question 21

compare isoflurane and halothane

Answer 21

isoflurane has less HoTN and arrhythmic effects; its association with reduced BP is due to decrease in systemic vascular resistance

Question 22

what are some disadvantages of sevoflurane

Answer 22

• metabolite is nephrotoxic
• unstable when exposed to carbon dioxide absorbents in anesthetic machines, also degrading to a compound that is potentially nephrotoxic

Question 23

list some examples of IV anesthetics

Answer 23

thiopentone, etomidate, propofol, ketamine, midazolam

Question 24

name the IV anesthetic which has analgesic properties

Answer 24

ketamine

Question 25

why are analgesics (eg. NSAIDs, Coxibs, opioids) usually used as adjuncts for GA

Answer 25

this is to reduce anesthetic requirements

Question 26

what precaution do we need to take when administering barbiturates and muscle relaxants?

Answer 26

must allow barbiturates to clear from IV line before administering muscle relaxants to prevent precipitations