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from Section 2 - Crises and Complications
Published online by Cambridge University Press: 09 June 2025
Local Anaesthetic Systemic Toxicity (LAST) can occur following an excessive dose of drugs administered into the tissues or from inadvertent venous or arterial administration. This may occur from the outset of the block or following a top up.
The clinical picture may include anxiety, restlessness, nausea, tinnitus, perioral tingling and tremor progressing to alteration on mental state, loss of consciousness and convulsions. In addition, cardiovascular collapse may occur from conduction blocks, ventricular arrhythmias or asystole.
Treatment is to stop injecting the LA, administer 100% oxygen, with tracheal intubation and seizure control if necessary. Hypotension and arrythmias are treated conventionally. Intravenous lipid emulsion (intralipid) 20% should be available and considered too. If cardiac arrest occurs, CPR should be started and may need to be prolonged (over an hour). If facilities are available, cardiopulmonary bypass may be needed too.
Reactions may also occur with the adrenaline used in LA mixtures and prilocaine induced methemoglobinemia.
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