Lidocaine / Mepivacaine (Local Infiltration — Plastics)

How it works

Both reversibly block neuronal voltage-gated sodium channels, halting impulse conduction; mepivacaine has a duration broadly similar to lidocaine and, unlike lidocaine, produces little local vasodilatation.

Prescribing in practice

• Inadvertent intravascular injection or excessive total dose can precipitate local-anaesthetic systemic toxicity with CNS and cardiovascular collapse, so aspirate before injecting, use the lowest effective dose and keep lipid emulsion available.
• If a preparation contains adrenaline, avoid infiltration around digits, nose, ears and other end-arterial territories where ischaemia is a concern.
• Reduce dose in hepatic impairment, the elderly and the debilitated, in whom amide clearance and tolerance are reduced.

Monitoring

Monitor for early signs of systemic toxicity during and after infiltration, particularly when larger volumes are used, with resuscitation equipment to hand.

Counselling the patient

• Numbness and loss of sensation in the area are expected and wear off over a few hours.
• Tell the team immediately if you feel dizzy, hear ringing, notice a metallic taste or feel your heart racing.

Evidence & guidelines

Maximum-dose limits and management of local-anaesthetic systemic toxicity with lipid emulsion are established in UK anaesthetic safety guidance.