W19/L5: Anaesthetics

Question 1

How do local anaesthetic agents work?

Answer 1

They interfere with Na+ influx to block action potentials in sensory nerves

Question 2

What’s an example of an aminoester anaesthetic?

Answer 2

Procaine

Question 3

What’s the duration of action of aminoesters like?

Answer 3

Relatively short ~30min

Question 4

Why do aminoesters have a short duration of action

Answer 4

they’re hydrolysed by esterases (including AChE)

Question 5

List 3 examples of aminoamide anaesthetics

Answer 5

Lignocaine
Bupivicaine
Ropivicaine

Question 6

Why are the aminoamide anaesthetics longer acting?

Answer 6

They’re metabolised hepatically

Question 7

What’s the local anaesthetic that doesn’t have a family?

Answer 7

Benzocaine

Question 8

What features of local anaesthetics make them safe?

Answer 8

They bind reversibly
There’s no permanent nerve damage
They are administered in a way that limits systemic distribution

Question 9

Describe the neural Na+ channel

Answer 9

Large protein with many TM domains.

Has two gates: M- and N-gate

Question 10

Where on the Na+ channel do toxins usually bind?

Answer 10

On the extracellular side - usually causing complete & irreversible blockage.

Question 11

Where on the Na+ channel do the local anaesthetics bind?

Answer 11

On the intracellular side

Question 12

What are the two mechanisms of local anaesthetics interacting with the Na+ channel?

Answer 12

Hydrophobic and hydrophilic

Question 13

How does the hydrophobic MoA of local anaesthetics work?

Answer 13

The drug in its uncharged form can enter the cell membrane and take position in the Na+ pore

Question 14

*Skip the rest of this cause I think JZ’s explanation is wrong. Look it up!

Answer 14

..

Question 15

What are the commonly inhaled GAs?

Answer 15

Desflurane
Sevoflurane
Isoflurane

Question 16

What are the common IV GA’s?

Answer 16

Propofol

Thiopentone

Question 17

How can GAs affect respiration?

Answer 17

Impaired ventilation
Depression of the resp. centre
Obstruction of airways due to retention of mucosal secretions

Question 18

Why are anti-muscarinics often co-administered with GAs?

Answer 18

They decrease secretion -> reducing the likelihood of airway obstruction.

Question 19

How can GAs affect the cardiovascular system?

Answer 19

Decrease vasomotor centre function
Depress contractility
Peripheral vasodilation
Cardiac arrhythmias
Inadequate response to fall in BP or CO

Question 20

What are the two theorised MoA of GAs?

Answer 20

Lipid theory & receptor interaction theory

Question 21

What is the lipid theory of GA MoA?

Answer 21

That GAs work by getting into the lipid membrane of axons, expanding and thus affecting activity

Question 22

What evidence supports the lipid theory of GA MoA?

Answer 22

• There;s a close correlation between lipid solubility and anaesthetic potency
• Hyperbaric chambers can reverse anaesthesia

Question 23

What is the receptor interaction theory of GA MoA?

Answer 23

That GAs work by enhancing inhibitory systems and inhibiting excitatory systems

Question 24

What evidence supports the receptor interaction theory of GA MoA?

Answer 24

? Not actually sure - look this up!

Question 25

What (broad) treatment goals do we have for Epilepsy?

Answer 25

Modify motor nerve output: Reduce exitation