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Intralipid for LAST — MFDS Part 1 MCQ

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HardPharmacologyIntralipid for LASTMFDS Part 1

During surgical removal of a mandibular third molar under intravenous midazolam and fentanyl sedation, a 31-year-old man receives a repeat bupivacaine inferior alveolar nerve block. He immediately reports a metallic taste and tinnitus, becomes agitated, has a generalised seizure, and then develops a pulseless broad-complex ventricular arrhythmia. Cardiopulmonary resuscitation and advanced life support are commenced. Which diagnosis specifically indicates administration of 20% intravenous lipid emulsion (Intralipid) as an additional resuscitation measure?

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Correct answer: E — Severe local anaesthetic systemic toxicity

The correct answer is E. Metallic taste, tinnitus and agitation immediately after a repeat bupivacaine dose, progressing to seizure and a malignant ventricular arrhythmia, are classic prodromal and severe features of local anaesthetic systemic toxicity (LAST). AAGBI guidance directs that, alongside stopping the local anaesthetic, securing the airway, treating seizures and starting CPR/ALS, severe cardiovascular toxicity is treated with 20% intravenous lipid emulsion: an initial bolus of 1.5 ml/kg over 1 minute followed by an infusion, to a maximum cumulative dose of 12 ml/kg. Proposed mechanisms include intravascular sequestration ('lipid sink') of lipophilic anaesthetics such as bupivacaine, plus metabolic and cardiotonic effects. The distractors have their own specific antidotes or management: paracetamol overdose is treated with acetylcysteine, opioid overdose with naloxone, benzodiazepine overdose supportively (flumazenil only in selected cases), and warfarin over-anticoagulation with vitamin K with or without prothrombin complex concentrate—none is an indication for lipid emulsion.

Reference: Association of Anaesthetists of Great Britain and Ireland (AAGBI). Safety Guideline: Management of Severe Local Anaesthetic Toxicity. 2010. https://www.bradfordhospitals.nhs.uk/wp-content/uploads/2019/06/AAGBI-Management-of-Severe-LA-Toxicity.pdf