12 LOCAL ANAESTHETICS

Question 1

What is the mechanism of action for local anaesthetics

Answer 1

Block voltage gated Na+ channels leading to lack of depolarisation- no AP.

Question 2

What pharmacokinetic property increases the potency of a LA

Answer 2

It lipid solubility determined by the length of the alkyl chain. Mute point as doses titrated for potency

Question 3

What pharmacokinetic property effects the duration of action

Answer 3

Protein binding, the higher the binding the longer the duration of action

Question 4

Two classes of LA

Answer 4

Esters and amides

Question 5

Name and ester

Answer 5

Cocaine,

Question 6

Name three amides

Answer 6

Prilocaine, bupivicain, lignocaine.

Question 7

Describe lignocaine

Answer 7

Fast onset, short duration, not potent.

Question 8

What determines the onset of action of a LA

Answer 8

The pKa (acid dissociation constant), low pKa fast onset

Question 9

Describe bupivicaine

Answer 9

Potent, long duration. Good for nerve blocks

Question 10

Describe ropivicaine

Answer 10

Slow onset, long action, less cardio toxic

Question 11

Describe prilocaine

Answer 11

Used in regional anaesthesia. Safe,

Question 12

Describe cocaine

Answer 12

Topical. Good for nose surgery. Ester

Question 13

What can happen in toxicity

Answer 13

Heart block, seizures, tinnitus, ventricular fibrillation

Question 14

Two forms of neuroaxial administration

Answer 14

Spinal and epidural

Question 15

Describe nerve block

Answer 15

I.e. pudendal nerve block