1% Lignocaine

Question 1

1% Lignocaine Mechanism of action

Answer 1

• Lignocaine is a local anaesthetic.
• Lignocaine blocks the initiation and transmission of nerve impulses by blocking the movement of sodium ions across the nerve cell membrane.

Question 2

1% Lignocaine Indications

Answer 2

Subcutaneous injection for prophylaxis of pain associated with IV cannulation.
Subcutaneous injection for digital ring blocks for analgesia.
Intraosseous injection for bone pain associated with fluid infusion via an intraosseous needle.

Question 3

1% Lignocaine Contraindications

Answer 3

Known severe allergy.

Local infection in the area of injection.

Question 4

1% Lignocaine Cautions

Answer 4

Taking an anticoagulant (ring blocks).

Question 5

1% Lignocaine Use in pregnancy

Answer 5

Safe, may be administered if indicated

Question 6

1% Lignocaine Subcutaneous Dose

Answer 6

a) The maximum subcutaneous dose for an adult is 200 mg (20 ml of 1% lignocaine).
b) See the paediatric drug dose tables for the maximum dose for a child.
c) The subcutaneous dose may be repeated once after 30 minutes.

Question 7

1% Lignocaine Intraosseous Dose

Answer 7

a) 50 mg (5 ml of 1% lignocaine) for an adult.
b) See the paediatric drug dose tables for a child.
c) The intraosseous dose may be repeated once after 15 minutes.

Question 8

1% Lignocaine Subcut for IV insertion Administration

Answer 8

Administer into the subcutaneous tissue at the site of cannulation. Raise a bleb and wait approximately one minute before insertion.

Question 9

1% Lignocaine Digital ring blocks Administration

Answer 9

Administer approximately 1-2 ml of 1% lignocaine into the

tissue on either side of the web space of the digit.

Question 10

1% Lignocaine IO Administration

Answer 10

Administer slowly over 1-2 minutes and wait one further minute before infusing fluid. This is intended to limit the amount of lignocaine flushed into the circulation.

Question 11

1% Lignocaine Common adverse effects

Answer 11

Stinging at site of injection

Question 12

1% Lignocaine Duration of action

Answer 12

30-60 minutes

Question 13

1% Lignocaine Usual Preparation

Answer 13

50mg in 5ml

Question 14

1% Lignocaine Usual onset of effect

Answer 14

• 1-2 minutes for IV cannulation.

* 5-10 minutes for digital ring blocks.

Question 15

1% Lignocaine Pharmacokinetics

Answer 15

• Lignocaine is metabolised in the liver.

* There are no significant effects from liver impairment on acute administration.

Question 16

1% Lignocaine Common interactions

Answer 16

None

Question 17

1% Lignocaine Additional information

Answer 17

Do not apply lignocaine topically to the eye because the solution contains apreservative that may cause harm.
• Warming lignocaine, for example in your pocket or hand, may reduce the stinging associated with subcutaneous injection.

Question 18

1% Lignocaine Lignocaine OD

Answer 18

Overdose of lignocaine when administered subcutaneously is very rare, but
can occur if doses exceed 3 mg/kg or more than 1 mg/kg is inadvertently
administered IV. If this occurs the following may develop:
Tingling around the mouth.
Seizures.
Dysrhythmias, particularly bradydysrhythmias.
Hypotension.
Cardiac arrest.

Question 19

Lignocaine Briefly explain transmission of nerve impulses across cell membrane, how does sodium ion blocking change this?

Answer 19

• Neurons generate electrical signals through brief, controlled changes in the permeability of their cell membrane to particular ions
• Inhibiting Sodium ion channels leads to the inability of the cell to depolarize, and stops it sending a pain signal