Local Anaesthetic

Question 1

How do local anaesthetics work

Answer 1

Block action potentials from travelling along a nerve by binding to intracellular sodium channels.

Question 2

Why wouldn’t local anaesthetics work in abscess cavity?

Answer 2

Because anaesthetics are bases so don’t work in acidic conditions

Question 3

Types of local anaesthetic

Answer 3

Intradermal and subcut (must aspirate first!), Emollient, Spinal and epidural, Regional

Question 4

Name 2 common local anaesthetics

Answer 4

Lidocaine, bupivicaine

Question 5

Maximum dose of lidocaine

Answer 5

3mg/kg (without adrenaline)

Question 6

Maximum dose of bupivicaine

Answer 6

2mg/kg

Question 7

What does toxicity depend on?

Answer 7

• Dose
• Rate of absorption
• Patient weight
• Drug (Bupivacaine>Lidocaine>Prilocaine)

Question 8

Signs of toxicity

Answer 8

• Light headedness,
• Sensory disturbance,
• Disorientation,
• Shiver,
• Tremor,
• Convulsions,
• Resp depression and ultimately cardiac distress.
• Ultimate complication is when the heart muscle/ sodium chloride are blocked leading to bradycardia and ultimately cardiac arrest.

Question 9

Management of toxicity

Answer 9

ABCDE, supportive care, intralipid (given IV) binds in plasma making it unable to enter nerves.

Question 10

List types of nerve block

Answer 10

• LA
• Field blocks - hernias repair
• Plexus block
• Limb blocks - femoral nerve + sciatic nerve
• Central neural - epidural, spinal

Question 11

What are 2 types of central block

Answer 11

• Spinal (subarachnoid space) COMPLETE BLOCK
• Epidural (extradural space) SEGMENTAL BLOCK

Question 12

Why is adrenaline given with local anaesthetic?

Answer 12

To vasoconstrict surrounding vessles, reducing bleeding and reducing systemic uptake.