Anaesthetics

Question 1

What is required from an anaesthetic?

Answer 1

Abolition of sensation and pain
Triad of general anesthesia
- Unconsciousness
- Analgesia
- Muscle relaxation
Multiple drugs

Question 2

What is the triad of general anesthesia

Answer 2

Unconsciousness
Analgesia
Muscle relaxation

Question 3

What are the characteristics of an ideal GA (general anaesthetic)

Answer 3

Stable
Potent
Non-toxic
Controllable
Rapid on and off
Adjustable
Minimal cardio and respiratory depression
Non-irritant

Question 4

Xenon is ideal why not use it?

Answer 4

It is expensive/rare

Question 5

How many stages of anaesthesia are there?

Answer 5

4

Question 6

What are the stages of aneasthesia

Answer 6

1. Analgesia
2. Excitement
3. Anaesthesia
4. Medullary paralysis (C/R Depression, lethal!)

Question 7

Combined approaches in surgical anaesthesia

Answer 7

Rapid unconsciousness
- IV with rapid, short acting agent (e.g thiopentone)

Maintain unconsciousness
- Inhalation agents e.g N2O and Halothane

Supplement analgesia
- IV e.g Fentanyl

Paralysis
- NMJ Block e.g succinylcholine

Question 8

Commonly used anaesthetics

Answer 8

Inhalation

• N20
• Halothane
• Enflurane
• Isoflurane
• Desflurane
• Ether, cyclopropane, chloroform

IV

• Thiopental
• Etomidate
• Propofol
• Ketamine
• Midazolam and other benzodiazepines

Question 9

What is the Lipid Theory of Anaesthetic Action

Answer 9

Potency proportional to lipid solubility

“Narcosis commences when any chemically indifferent substance has attained a certain molar concentration in the lipids of the cell”

Question 10

What is the Protein Theory of Anaesthetic Action

Answer 10

Anaesthetics interact with membrane proteins

Receptors and ligand gated ion channels

Question 11

According to the protein theory how do GAs work? (not the definition)

Answer 11

Potentiate inhibitory receptors
Block excitatory receptors
Affect ion channels (decrease NA influx and increase K efflux)