Lignocaine

Pharmacology & Uses

Lignocaine (lidocaine) is the most widely used local anaesthetic — an amide with a rapid onset and moderate duration. It is highly versatile: used for infiltration, nerve blocks, topical/surface anaesthesia, spinal and epidural anaesthesia, and intravenous regional anaesthesia. Maximum dose 3 mg/kg plain, 7 mg/kg with adrenaline.

Other Uses

Lignocaine has important non-anaesthetic uses: it is a class Ib antiarrhythmic for ventricular arrhythmias, and intravenous lignocaine is used to blunt the pressor response to laryngoscopy and to reduce propofol injection pain. It is generally well tolerated within the dose limit.

Toxicity & Safe Use

Although lignocaine is among the safer local anaesthetics, it still causes systemic toxicity if the maximum dose is exceeded or it is injected intravascularly, beginning with the usual neurological warning signs, so the same precautions of dose calculation, aspiration and incremental injection apply. Its versatility means it appears in many forms — plain and adrenaline-containing solutions of various strengths, gels, sprays and patches — and it is important to account for all sources when several preparations are used together so that the cumulative dose stays within the safe limit.

Note

It is worth recalling that intravenous lignocaine has a recognised role in blunting the cardiovascular response to laryngoscopy and in reducing the pain of a propofol injection.

The reference local anaesthetic — versatile and predictable.

• Lignocaine: commonest LA; amide; rapid onset, moderate duration; 3 mg/kg (7 with adrenaline).
• Versatile: infiltration, nerve block, topical, spinal/epidural, IV regional.
• Also a class Ib antiarrhythmic (ventricular); blunts laryngoscopy pressor response.