Local Anaesthetic

Question 1

How do LA’s achieve differential block?

Answer 1

Smaller fibres (pain and temp) more sensitive than large ones meaning that they are blocked, but not large proprioception and coarse touch fibres

Question 2

What do you always give Lidnocaine with?

Answer 2

Vasconstrictor

Question 3

What is the duration of Lidnocaine?

Answer 3

90 mins

Question 4

What is a longer acting LA?

Answer 4

Bupivicaine (8 hour duration, 30 mins onset)

Question 5

What are longer active LAs used for?

Answer 5

Labour spinals

Question 6

What is the mechanism of LA?

Answer 6

Blocks Na channels by binding to the receptor so no action potentials and insufficient depolarisation

Question 7

What are the potential CV side effects of LAs?

Answer 7

Cardiovascular: Vasodilation and reduced BP- therefore vasoconstrictors given to prolong action of drug too

Question 8

What are the CNS side effects of LAs?

Answer 8

Mild: Light headed, Anxious
Moderate: Visual disturbance
Severe: Convulsions and come, respiratory and cardiac depression as Medulla affected