Local Anaesthetics

Question 1

What are some indications for local anaesthesia

Answer 1

Procedural, inc endoscopy throat spray
Acute pain eg labour - epidural
Nerve/plexus blocks
Chronic pain eg joint/spinal injections
Spinal (subarachnoid) anaesthesia for surgery
IV regional anaesthesia

Question 2

Why is adrenaline added to local anaesthetics?

Answer 2

Prolongs the action by reducing systemic absorption
Reduces bleeding via vasoconstriction

NB do not use adrenaline in fingers/toes/pinna/nose/penis

Question 3

Contraindications of local anaesthetic

Answer 3

Known hypersensitivity
Finger/toe etc with adrenaline
Heart block, wolf-parkinson-white

Question 4

Side effects of local anaesthetic administration

Answer 4

Procedural eg infection/bleeding
Nerve damage- 90% resolves in 6 weeks
Methaemoglobinaemia
Hypotension, bradycardia

Question 5

Which drugs interact with lidocaine?

Answer 5

MAOIs/TCAs/vasopressors- can cause profound hypertension if an adrenaline containing preparation is used

Question 6

How do local anaesthetics work?

Answer 6

Block fast voltage gated sodium channels - axon cannot depolarise so no action potential is sent. Also class i antiarrhythmics

Question 7

How can the pain of LA infiltration be reduced?

Answer 7

Warm to 37, add bicarbonate

Question 8

How is lidocaine eliminated?

Answer 8

Via the kidneys

Question 9

What is the maximum dose of lidocaine?

Answer 9

3mg/kg without, or 7mg/kg with adrenaline