Anaesthesia

Question 1

What is the mode of action of Curare?

Answer 1

Nicotinic acetylcholine receptor antagonist (nAChR)

Question 2

What is the mode of action of Atropine?

Answer 2

Muscarinic acetylcholine receptor antagonist (mAChR)

Question 3

What is the mode of action of Phenobarbital? What is it used for?

Answer 3

GABA receptor agonist, increasing the flux of Cl- into a neurone which decreases its excitability. Used to treat epilepsy.

Question 4

What is MAC (Minimum Alveolar Concentration)?

Answer 4

The concentration of a vapour in the lungs required to prevent movement in 50% of patients

Question 5

What are the two groups of general anaesthetics?

Answer 5

Intravenous general anaesthetics

Volatile general anaesthetics

Question 6

Give three examples of general anaesthetics which are volatile

Answer 6

Nitrous Oxide
Isoflurane
Sevoflurane

Question 7

What is the mechanism of action of Isoflurane?

Answer 7

Neuronal ion channel modulator, it decreases the conductance of a neurone by decreasing the opening time and increasing the closing time

Question 8

Give three examples of general anaesthetics which are intravenously administered

Answer 8

Propofol
Ketamine
Thiopental

Question 9

Describe the mechanism of action of Propofol?

Answer 9

GABA modulator, slowing down its closure. In high doses can activate GABA receptors also.

Question 10

Why don’t Local anaesthetics generally work well in acidic environments such as in an abscess?

Answer 10

Because most Local anaesthetics are alkaline

Question 11

Outline the three classes of pain fibres; what their sizes are and whether they are myelinated or not.

Answer 11

A fibres: Large diameter, with myelination
B fibres: Small diameter, with myelination
C fibres: Small diameter, unmyelination

Question 12

Local anaesthetics will tend to work on which pain fibres more quickly? What might be the symptoms?

Answer 12

C fibres, due to its small diameter and unmyelination. Clinical findings include warm dry feet and vasodilation and hypotension

Question 13

What are the two groups of Local anaesthetics and how do they work?

Answer 13

Antagonistic LAs: Block receptors, non-depolarising

Agonistic LAs: Activative receptors, strongly depolarising

Question 14

Give 2 examples of Antagonistic Local anaesthetics and explain how they work

Answer 14

Tubocurare and Atracurium, which are NAChR antagonists preventing NMJ transmission

Question 15

Reversal agents such as Neostigmine are given following what class of drugs? How does Neostigmine work?

Answer 15

Neostigmine is administered as a reversal agent for Antagonistic, non-depolarising LAs. Act as an Acetylcholinesterase inhibitor to increase ACh in the NMJ for longer

Question 16

Give 1 example of Agonistic Local anaesthetic and explain how they work

Answer 16

Suxamethonium, which is a mimic for ACh, causing depolarisation across the NMJ

Question 17

What can be given in conjunction with Agonistic Local anaesthetics such as Suxamethonium to help potentiate it better? How does it work?

Answer 17

Neostigmine, which is an Acetylcholinesterase Inhibitor which will increase ACh in the NMJ longer and depolarise across the NMJ for longer