Local anesthetic systemic toxicity is a rare but potentially fatal complication of regional anesthesia and local anesthetic infiltration. The introduction of intralipid emulsion therapy has dramatically improved outcomes, but prevention through careful dosing, ultrasound guidance, incremental injection with aspiration, and use of test doses remains the primary safety strategy.
CNS symptoms (tinnitus, metallic taste, seizures) typically precede cardiovascular toxicity (arrhythmias, cardiac arrest)
20% Intralipid rescue: 1.5 mL/kg bolus, then 0.25 mL/kg/min infusion; repeat bolus x2 if unstable
Maximum doses: lidocaine 4.5 mg/kg (7 with epi), bupivacaine 2.5 mg/kg, ropivacaine 3 mg/kg
Bupivacaine has highest cardiotoxicity-to-CNS toxicity ratio (can present with arrhythmia first)
Ultrasound guidance for regional blocks significantly reduces LAST incidence by improving injection precision
Keep 20% intralipid immediately available wherever regional anesthesia is performed. The ASRA checklist recommends having it in a dedicated kit, not in the pharmacy. In cardiac arrest from LAST, avoid vasopressin, calcium channel blockers, beta-blockers, and lidocaine. Reduce epinephrine doses to <1 mcg/kg.
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