Seizure and Wide QRS Four Minutes After a Supraclavicular Block

Diagnosis: local anaesthetic systemic toxicity (LAST) with neurological prodrome, generalised seizure and early cardiotoxicity (wide QRS). The QRS widening predicts imminent arrest, so treatment must be aggressive and simultaneous, not sequential.

1. Stop injecting immediately and call for help and for the LAST checklist; note the time of onset.
2. Airway and oxygenation: 100% oxygen by face mask, suctions ready, and early tracheal intubation if GCS remains low or the airway is at risk, using a reduced induction dose because of cardiovascular compromise. Hypoxia, hypercarbia and acidosis all potentiate local anaesthetic cardiotoxicity.
3. Terminate the seizure: midazolam 5 mg IV (or diazepam 10 mg). Propofol is a poor choice for seizure control here because it worsens hypotension and delivers far too little lipid.
4. Lipid emulsion 20%, lean body weight: bolus 1.5 mL/kg = about 108 mL (give 100 mL) IV over 1 minute, then infusion 15 mL/kg/h = about 1080 mL/h. Repeat the bolus once or twice at 5-minute intervals if circulation does not recover. Maximum cumulative dose 12 mL/kg (about 860 mL).
5. Hypotension: crystalloid bolus, then adrenaline boluses of no more than 1 microgram/kg and an infusion at 0.05–1 microgram/kg/min. Vasopressin, calcium channel blockers, beta-blockers and amiodarone are contraindicated.
6. Monitor: continuous ECG, arterial line, capnography, temperature; treat broad-complex arrhythmia with sodium bicarbonate 1–2 mmol/kg if the QRS remains wide.
7. Do not proceed with surgery and do not top up the block; arrange HDU/ICU and monitor for at least 4–6 hours after successful resuscitation because of recurrence.

Dose and technique, not bad luck. 40 mL of 0.5% bupivacaine contains 200 mg; for 72 kg this is about 2.8 mg/kg, above the conventional maximum of 2 mg/kg for plain bupivacaine and above the 2.5 mg/kg sometimes quoted with adrenaline. Adrenaline-containing solutions allow a marginal increase, not a 40% overrun.

Contributory factors:

• The supraclavicular space lies immediately adjacent to the subclavian artery and pleura and is highly vascular; negative aspiration on two occasions does not exclude intravascular needle placement.
• Injection over 90 seconds for 40 mL is fast. Slow, incremental injection of 3–5 mL with repeated aspiration and continuous ultrasound visualisation of the needle tip and the spread is standard.
• Adrenaline in the mixture masks early tachycardia and contributes to arrhythmia if given intravascularly.
• A 0.25–0.375% concentration with a smaller volume (for example 30 mL of 0.375% = 112 mg, 1.56 mg/kg) gives equally good surgical anaesthesia with far less toxicity risk.

Alternative for the other wrist: interscalene or supraclavicular block is unnecessary for a distal radius; an infraclavicular or axillary block uses less local anaesthetic and is further from major vessels, or the case could be done under general anaesthesia or a wide-awake local technique. If a block is chosen, use 25–30 mL of 0.375% bupivacaine or a lidocaine–bupivacaine mixture, keep total dose documented, and discuss the event with the patient using a structured explanation. Report it to the local incident system.

This is a LAST arrest, and the modifications are substantial.

1. Start CPR immediately and expect a long resuscitation - cases lasting well over an hour with good neurological recovery are described. Do not stop early on the basis of the usual rhythms or timings.
2. Continue lipid: give a further 1.5 mL/kg bolus (about 100 mL) and continue the 15 mL/kg/h infusion, respecting the 12 mL/kg total; if the infusion has been running, keep going during CPR and give additional boluses.
3. Adrenaline in small boluses only (1 microgram/kg, i.e. 10–70 micrograms), not the 1 mg doses of standard ACLS, which worsen ventricular arrhythmia in local anaesthetic toxicity. Avoid vasopressin, beta-blockers, calcium channel blockers and amiodarone.
4. Treat wide-complex rhythm with sodium bicarbonate 1–2 mmol/kg; magnesium for torsades. Defibrillate shockable rhythms as usual.
5. Airway early: 100% oxygen, capnography, and avoid hyperventilation. Correct hypoxia, acidosis, hypothermia, hypovolaemia and electrolyte disturbance.
6. Escalate to extracorporeal support: call the cardiothoracic/ECMO team early for veno-arterial ECMO or cardiopulmonary bypass if there is no return of spontaneous circulation after about 30–60 minutes of good-quality resuscitation - this is the definitive rescue for refractory LAST.
7. After ROSC: ICU, at least 4–6 hours of continuous monitoring, serial ECG and biochemistry, and consider metHb or rhabdomyolysis studies; the block will still be effective, so the limb must be protected and the patient must not be left unattended.