Anaesthesia

Question 1

Name 5 inhalational agents.

Answer 1

• Sevoflurane
• Isoflurane
• Desflurane
• Nitrous oxide
• Xenon

Question 2

Name 4 intravenous agents.

Answer 2

• Propofol
• Etomidate
• Barbiturates
• Ketamine

Question 3

What properties are ideal for inhalational agents?

Answer 3

Non-flammable
Stable
High potency
Fast onset

Question 4

What 3 factors are involved in the triad of balanced anaesthesia?

Answer 4

• Unconsciousness
• Analgesia
• Muscle relaxation

Question 5

Why is a combination of agents normally used?

Answer 5

Safer than a large single dose.

-minimises side effects

Question 6

How is potency measured in anaesthetics? (2)

Answer 6

• INHALED: Minimum Alveolar Concentration (MAC)

- IV: Cp50

Question 7

What is the minimum alveolar concentration (MAC)?

Answer 7

Concentration of vapour in lungs needed to prevent movement in 50% of subjects.

Question 8

What is Cp50?

Answer 8

Minimum plasma concentration needed to prevent movement in 50% of subjects.

Question 9

What is the Meyer Overton theory?

Answer 9

Describes correlation between lipid solubility of anaesthetics & MAC.
» suggests anaesthesia occurs when sufficient molecules dissolve in the lipid cell membrane.

Now shown to be false.

Question 10

How can neurobiological effects of anaesthetics be classified?

Answer 10

By effects on different receptors.

Question 11

What are the clinical features of group 1 (etomidate, propofol, pentobarbital)?

Answer 11

• Strong hypnotics
• Strong amnestics
• Weak immobilisers
• Slow cortical EEG

Question 12

What is the ratio of MAC-imob to MAC-awake for group 1 (etomidate, propofol, pentobarbital)?

Answer 12

4

Question 13

What are the molecular targets of group 1 (etomidate, propofol, pentobarbital)?

Answer 13

GABAa receptors.

Question 14

What are the clinical features of group 2 (NO, ketamine, xenon, cyclopropane)?

Answer 14

• Weak hypnotics
• Weak immobilisers
• Potent analgesics
• No EEG slowing

Question 15

What is the ratio of MAC-imob to MAC-awake for group 2 (NO, ketamine, xenon, cyclopropane)?

Answer 15

1.5(N2O) - 2 (Xe)

Question 16

What are the molecular targets of group 2 (NO, ketamine, xenon, cyclopropane)?

Answer 16

• NMDA receptors
• AMPA receptors
• Neuronal nAChRs
• 2 pore K+ channels

Question 17

What are the clinical features of group 3 (Halogenated ethers & alkanes)?

Answer 17

• Strong hypnotics
• Strong amnestics
• Strong immobilisers
• Slow cortical EEG

Question 18

What is the ratio of MAC-imob to MAC-awake for group 3 (Halogenated ethers & alkanes)?

Answer 18

2-3

Question 19

What are the molecular targets of group 3 (Halogenated ethers & alkanes)?

Answer 19

• GABAa receptors
• Glycine receptors
• Glutamate receptors
• Neuronal nAChRs
• 2 pore K+ channels

Question 20

What does low solubility of inhalation agents lead to?

Answer 20

Fast onset & quick recovery.

Question 21

What are low solubility inhalation agents most commonly used for?

Answer 21

Maintenance.

Question 22

What action do highly fat soluble agents have?

Answer 22

Slow equilibrium & perfusion in fat.

|&raquo_space; accumulation (‘hangover effect’)

Question 23

Which inhalation agent has a MAC value of 100%?

Answer 23

Nitrous oxide.

Question 24

Which inhalation agent has a very high oil:gas ratio, and a slower recovery?

Answer 24

Halothane

Question 25

What sort of action so IV agents have?

Answer 25

• Quick onset

- Short duration

Question 26

What are IV agents most commonly used for?

Answer 26

Induction.

Question 27

What are possible side effects of general anaesthetics? (3)

Answer 27

• Vasodilation
• Decrease cardiac contractility
• Can affect organ perfusion

Question 28

What are possible side effects of inhalational agents?

Answer 28

• Malignant hyperthermia

- Hepatotoxicity

Question 29

What are possible side effects of IV agents?

Answer 29

• Allergy

- Pain on injection