Local anaesthetic systemic toxicity (LAST) has occurred after an interscalene nerve block. After initial seizure control with benzodiazepines, the patient develops pulseless ventricular tachycardia. The FIRST definitive treatment per current guidelines is:

• A Intravenous sodium bicarbonate 1 mEq/kg
• B Intravenous amiodarone 300 mg
• C Immediate cardioversion at 200 J biphasic
• D 20% lipid emulsion 1.5 mL/kg IV bolus ✓

Explanation

For LAST-associated cardiovascular collapse, 20% lipid emulsion (intralipid) is the treatment of choice per AAGBI/ASRA guidelines. The initial bolus of 1.5 mL/kg is given over 1 minute, followed by infusion at 0.25 mL/kg/min; repeat bolus can be given for persistent cardiovascular instability. Lipid sink theory proposes that the lipid phase sequesters the hydrophobic local anaesthetic from cardiac tissue, reducing toxicity. CPR should be continued simultaneously. Amiodarone should be avoided in LAST because it exacerbates sodium channel blockade and worsens toxicity. Sodium bicarbonate may assist by alkalinising and promoting protein binding of LA but is adjunctive, not first-line for VT.

Reference: Morgan & Mikhail's Clinical Anesthesiology, 6th ed.

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Written and medically reviewed by the StethoPrep medical team.