Lidocaine hydrochloride

How it works

It blocks voltage-gated sodium channels in nerve and cardiac tissue, preventing the inflow of sodium needed for action-potential propagation and thereby producing reversible local anaesthesia and suppression of ventricular ectopy.

Prescribing in practice

• Inadvertent intravascular injection or exceeding the maximum safe dose can cause local anaesthetic systemic toxicity, with central nervous system signs (perioral tingling, seizures) and cardiovascular collapse; aspirate before injecting and have lipid emulsion rescue available.
• Plain lidocaine without a vasoconstrictor has a shorter duration than adrenaline-containing preparations, and dosing must be reduced in hepatic impairment and cardiac failure.
• Avoid solutions containing adrenaline in or around end-arterial fields such as digits and appendages, and reduce doses at the extremes of age.

Monitoring

Monitor for early features of systemic toxicity and, when used intravenously for arrhythmia, monitor ECG and cardiovascular status.

Counselling the patient

• Numbness from the injection will wear off over a few hours; avoid injury to the numb area until sensation returns.
• Tell the team straight away about ringing in the ears, a metallic taste, dizziness or tingling around the mouth.
• A brief stinging sensation on injection is normal.

Evidence & guidelines

Lidocaine is a long-established amide local anaesthetic, and safe-dosing and management of local anaesthetic systemic toxicity follow AAGBI/Association of Anaesthetists guidance.