Local anesthetic systemic toxicity (LAST)

Treat LAST differently from standard ACLS: secure the airway, stop seizures with a benzodiazepine, give 20% lipid emulsion early, use small epinephrine doses, avoid vasopressin, beta-blockers, calcium channel blockers and more local anesthetic, and observe after recovery.

1. Call for help early. The ASRA 2020 checklist starts with calling for help, getting the LAST rescue kit, considering lipid emulsion early and alerting a cardiopulmonary bypass team ¹.
2. Airway and seizures come first. Ensure an adequate airway; benzodiazepines are preferred for seizures, and if only propofol is available use low doses, such as 20 mg increments ¹.
3. Lipid dosing for adults over 70 kg. Give about 100 mL of 20% lipid over 2–3 minutes, then infuse about 250 mL over 15–20 minutes, by hand, roller clamp or pump ¹.
4. Weight-based lipid under 70 kg. Give about 1.5 mL/kg over 2–3 minutes, then about 0.25 mL/kg/min, using a pump if under 40 kg ¹.
5. Escalate if instability persists. Repeat the bolus or double the infusion, continue lipid at least 15 minutes after stability, and do not exceed about 12 mL/kg ¹.
6. Modify cardiac resuscitation. Start epinephrine below 1 mcg/kg; avoid vasopressin, calcium channel blockers, beta-blockers and further local anesthetic. Cardiac arrest can follow toxic convulsions after unintentional intravascular bupivacaine ¹³.

Presentation may be delayed: ultrasound guidance, local infiltration techniques and continuous infusions shift LAST toward later onset, and events increasingly occur outside hospitals ².

• The order of lipid administration (bolus or infusion) and the method of infusion are not critical ¹.
• Observe at least 2 hours after a seizure and 4–6 hours after cardiovascular instability ¹.
• Small patient size and sarcopenia increase LAST risk; although single institutions report lower frequency, many events still occur in the community ².
• Lipid reversal mechanisms include rapid partitioning, direct inotropy and post-conditioning ².
• Ultrasound guidance plays a preventive role, with fewer intravascular injections ².
• Prevention per the bupivacaine label: incremental 3–5 mL doses, slow injection with frequent aspiration, an epinephrine-containing test dose before epidurals, and IV access for major blocks ³.
• Bupivacaine carries a boxed warning for cardiac arrest with difficult resuscitation during obstetric epidural use, mostly with the 0.75% concentration ³.
• The 2020 checklist was revised from user feedback, simulation studies and new evidence ⁴.

• Giving standard-dose epinephrine or vasopressin as in ACLS ¹.
• Treating seizures with large propofol doses ¹.
• Waiting to give lipid until cardiac arrest ¹.
• Using 0.75% bupivacaine for obstetric epidural anesthesia ³.