GA

Question 1

What is MAC and what does it confer in terms of potency?

Answer 1

Minimum alveolar concentration: Min conc of inhaled GA in the alveolar air that will produce immobility in 50% of patients exposed to a painful stimuli.

Low MAC = High potency

Question 2

Describe the mechanism of action by inhaled GA

Answer 2

1. Enhance inhibitory neurotransmission by increasing GABA receptor sensitivity to GABA
2. Depress excitatory neurotransmission by decreasing NMBA receptor activity

Question 3

How is inhaled anaesthetic eliminated?

Answer 3

Through expired air

*EXCEPT SEVOFLUORANE that is eliminated via hepatic metabolism

Question 4

What is the principal adverse effect of GA?

Answer 4

Respiratory depression (IV)
Cardiac performance (IV and inhaled)

Question 5

Describe the use of nitrous oxide

Answer 5

NO has higher MAC (less potent) and low blood solubility (rapid onset and recovery)

High analgesic property but cannot be used alone to produce GA effects, must combine with other gases

Question 6

Induction of anaesthesia is usually accomplished with a short- acting barbiturate like _

Answer 6

Thiopentone

Question 7

Describe ketamine (clinical uses & adverse effects)

Answer 7

Given through IV and it is a dissociative anaesthesia. Can cause sedation, immobility, analgesic and amnesia.

Adverse effect: Unpleasant psychologic reactions (hallucination, disturbing dreams, delirium) during recovery

Question 8

What are some examples of low MAC inhaled GAs? Rank them in terms of their MAC.

Answer 8

Halothane > Isoflurane > Sevoflurane

Question 9

What is the benefit of combining inhaled and IV anaesthetics?

Answer 9

1. Allows the dosage of inhalation agent to be reduced (reduce adverse effects and speed up recovery)
2. Prolong duration of anaesthetic effect

Question 10

What is major adverse effect of IV GA?

Answer 10

Respiratory Depression

Question 11

List 3 IV GAs

Answer 11

1. Thiopentone
2. Propofol
3. Ketamine

Question 12

Describe propofol (clinical uses & adverse effects)

Answer 12

Clinical use: Rapid onset and fast recovery. Extensively used in day surgeries

Adverse effects: Cardiovascular effects leading to hypotension. To be used with caution in elderly, patients with compromised cardiac function and hypovolemic patients

Question 13

List the 4 anaesthetic adjuncts

Answer 13

1. Benzodiazepines: Midazolam
2. Alpha 2 adrenergic agonists: Dexmedetomidine
3. Analgesics: Opioids or NSAIDs (minor)
4. Neuromuscular blocking agents: Succinylcholine and Pancuronium