GA

Question 1

Which inhaled general anaesthetic has some significant metabolic degradation from CYP450 enzymes?

Answer 1

Halothane. Approximately 20% metabolised.

Question 2

Which three inhaled anaesthetics are most likely to have liver toxicity (in descending order of likelihood)?

Answer 2

Halothane
Isoflurane
Desflurane

Question 3

If you were seeking a more potent anaesthetic, would you want a smaller or higher MAC?

Answer 3

Smaller. If it’s a smaller concentration required to produce no response to surgical stimulus, that implies a higher potency.

Question 4

Lipid solubility is directly proportional or inversely proportional to MAC?

Answer 4

Inversely proportional.

An increasing lipid solubility indicates a more potent anaesthetic, meaning less concentration for an effective dose, i.e. lower MAC.

Question 5

What do gaseous anaesthetics do on a cellular level?

Answer 5

Stabilise the open state of the GABAA receptor and stabilise the closed or desensitised state of the nicotinic receptor.

Question 6

How do fatty tissues affect anaesthesia?

Answer 6

It acts as a resevoir for the anaesthetic during recovery, lengthening the time of recovery.

Question 7

How significant is metabolic degradation of inhaled anaesthetics?

Answer 7

It is very insignificant. It is more important to monitor induction/recovery and respirations to determine duration of action.

Question 8

What is MAC?

Answer 8

Minimum alveolar concentration required to have 50% of humans to have no surgical response.

Question 9

If a patient has mainly lean tissues, will they reach anaesthetic equillibrium quicker or slower?

Answer 9

Quicker.

Question 10

What anaesthetics can cause a sympathetic discharge?

Answer 10

Nitrous oxide and ketamine.

Question 11

Intravenous anaesthetics have a duration of action that is long or short?

Answer 11

Short.
Thiopentone: 5-10mins.
Propofol: 2-4mins

Question 12

What are the stages of anaesthesia (Guedel’s signs)? What does each mean clinically?

Answer 12

1. Induction (Pt doesn’t respond to questions)
2. Excitement (Pt struggles, coughs, may experience bronchospasm and vomitting)
3. Surgical anaesthesia
4. Medullary depression (Leads to cardiorespiratory collapse - is a state of overdose)

Question 13

Propofol and thiopentone, which one is the barbituate?

Answer 13

Thiopentone.

Question 14

Name the five in-use inhaled general anaesthetics.

Answer 14

Nitrous Oxide
Sevoflurane
Haloflurane
Isoflurane
Desflurane

Question 15

Low solubility (low blood/gas coefficient) indicates what about the rate of induction and what about the rate of recovery?

Answer 15

Fast rate of induction and fast rate of recovery.

Question 16

High solubility (high blood/gas) coefficient indicates what for rate of induction and what for rate of recovery?

Answer 16

Slow rate of induction and recovery.

Question 17

Regarding inhaled general anaesthetics, halogenation increases or decreases potencty?

Answer 17

Increases potency.

Question 18

If a patient’s rate of ventilation is increased, what happens to the rate of induction?

Answer 18

It increases as well.

Question 19

What are some effects on the CVS from inhaled anaesthetics?

Answer 19

Decreased heart contractility (halothane first, then D/I/S)
Decreased sympathetic activity (halothane and sevflurane)
Decreased systemic vascular resistance (des/iso/sev)
Arrythmias (halo, D/I/S)

Question 20

Intravenous anaesthetics are not suitable for?

Answer 20

Maintaining anaesthesia.

Question 21

What are the five aims of ‘balanced anaesthesia’?

Answer 21

LOC
Amnesia
Relaxation of skeletal muscle 
Analgaesia 
Blunting of ANS responses

Question 22

Which of the intravenous anaesthetics has less chance of producing respiratory depression?

Answer 22

Ketamine.

Question 23

Intravenous anaesthetics have a duration of action that is long or short?

Answer 23

Short.
Thiopentone: 5-10mins.
Propofol: 2-4mins