Anaesthetic emergencies

Local anaesthetic systemic toxicity (LAST)

Overview and approach

Systemic local-anaesthetic toxicity can cause neurological symptoms, seizures and cardiovascular collapse.

ANZCA advises that 20% lipid emulsion be immediately available wherever potentially toxic volumes of local anaesthetic are used (1).
Usually caused by accidental intravascular injection or rapid absorption from vascular sites, such as intercostal blocks or mucous membranes (5). Toxicity can occur some time after the initial injection (2).
Maximum doses (guide only): lignocaine 3 mg/kg plain (5); lignocaine 7 mg/kg with adrenaline (6); bupivacaine 2 mg/kg (5); prilocaine 6 mg/kg (5). Product information says these are a guide only, and the safe dose may be substantially lower in patients with acute or chronic disease (6).
1 mL of 1% lignocaine = 10 mg (5).

Assessment and clinical features

Recognise symptoms during/after injection, stop administration and call emergency help.

Early (CNS excitation): circumoral or tongue numbness, light-headedness, tinnitus, visual disturbance, slurred speech, restlessness, shivering, muscle twitching or tremor. Hypertension and tachycardia may occur early (4)(5).
Severe: sudden change in mental state, severe agitation or loss of consciousness, with or without tonic-clonic seizures (2).
Cardiovascular: sinus bradycardia, conduction blocks, asystole and ventricular tachyarrhythmias. Cardiotoxicity can occur rapidly with little warning (2)(6).

Differentials and investigations

ABCDE, ECG and specialist/resuscitation assessment; presentations may be delayed or predominantly cardiovascular.

Consider drawing blood for analysis, but do not delay definitive treatment (2).
Acidosis and hypoxia increase the risk and severity of toxicity, so ventilate well. Hyperventilation may help when there is metabolic acidosis (2)(6).

Management and follow-up

Follow the current LAST rescue checklist, including appropriate airway/seizure care and lipid-emulsion therapy by the resuscitation team.

Stop injecting, call for help, airway and 100% oxygen, IV access, control seizures with a benzodiazepine (2)(3). Lipid emulsion 20%: bolus then infusion per the checklist, repeat if unstable and continue after stability, with a maximum total dose (3). Avoid lidocaine, beta-blockers, calcium-channel blockers and vasopressin; use low-dose adrenaline for hypotension (3). Observe for 2 hours after a seizure and 4-6 hours after cardiovascular instability (3).
Seizures: benzodiazepine preferred. If only propofol is available, give small doses (e.g. 20 mg increments) (3).
20% lipid emulsion, ASRA checklist (2020): give early; the order of bolus and infusion is not critical (3).
- Under 70 kg: bolus about 1.5 mL/kg over 2-3 minutes, then infuse about 0.25 mL/kg/min (consider a pump if under 40 kg) (3).
- Over 70 kg: bolus about 100 mL over 2-3 minutes, then infuse about 250 mL over 15-20 minutes (3).
- If still unstable: repeat the bolus and double the infusion. Continue for at least 15 minutes after haemodynamic stability. Maximum dose about 12 mL/kg (3).
AAGBI 2010 regimen (ANZCA-endorsed; used in some Australian kits): 1.5 mL/kg over 1 minute plus infusion at 15 mL/kg/h. After 5 minutes, give up to two repeat boluses 5 minutes apart and double the infusion to 30 mL/kg/h if needed. Maximum cumulative dose 12 mL/kg, which is about 840 mL for 70 kg (2)(4).
Arrhythmia or hypotension: use smaller-than-usual adrenaline doses (start at ≤1 microgram/kg). Avoid local anaesthetics (including lignocaine as an antiarrhythmic), beta-blockers, calcium-channel blockers and vasopressin (2)(3). Propofol is not a substitute for lipid (2).
Cardiac arrest: start CPR and continue it throughout lipid therapy. Arrhythmias may be very refractory, and recovery may take more than 1 hour. Consider cardiopulmonary bypass if available (2)(3).
Follow-up: observe 2 hours after a seizure and 4-6 hours after cardiovascular instability, in a monitored area (2)(3). After lipid, exclude pancreatitis with clinical review and daily amylase or lipase for 2 days (2). Report the incident and lipid use (international registry, lipidregistry.org) (2).

Red flags and clinical pearls

Dose limits, incremental injection and monitoring reduce risk but do not eliminate it; standard resuscitation drug choices may need modification.

LAST resuscitation differs from standard ALS: lower adrenaline doses, no lignocaine, no vasopressin (3).
Calculate the maximum dose before injecting, and inject slowly with frequent aspiration (5)(6).
Know where the nearest lipid emulsion is kept before starting any block (2)(4).

References

Last updated from Sen’s notes on 9 October 2026.