Bupivacaine cardiotoxicity — FRCA Primary MCQ

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HardPharmacologyBupivacaine cardiotoxicityFRCA Primary

During an interscalene block, a patient develops circumoral tingling followed by a broad-complex arrhythmia after incremental injection of local anaesthetic. Which mechanism best explains the cardiovascular toxicity?

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Correct answer: C — Voltage-gated sodium channel blockade

Local anaesthetics block voltage-gated sodium channels; bupivacaine binds avidly to cardiac sodium channels and can cause refractory arrhythmias. β2-adrenoceptor stimulation would more likely cause tremor and tachycardia, not conduction block. Muscarinic blockade and cyclo-oxygenase inhibition do not explain seizures with arrhythmia after a nerve block. Early recognition of local anaesthetic systemic toxicity and lipid emulsion therapy is lifesaving.

Reference: Peck, Hill & Williams Pharmacology for Anaesthesia and Intensive Care; Association of Anaesthetists LAST guidance