What is the LAST protocol?

LAST (Local Anesthetic Systemic Toxicity) is a life-threatening emergency caused by toxic plasma levels of local anesthetics. The LAST protocol involves immediate lipid emulsion therapy (Intralipid 20%), seizure management with benzodiazepines, and prolonged CPR if cardiac arrest occurs. Early signs include metallic taste, tinnitus, and perioral numbness.

What is the lipid emulsion dose for LAST?

For adults >=70 kg: bolus 100 mL of 20% lipid emulsion over 2-3 minutes, then infusion 250 mL over 15-20 minutes. For adults <70 kg and pediatrics: bolus 1.5 mL/kg over 2-3 minutes, then infusion 0.25 mL/kg/min. Maximum total dose is 12 mL/kg for adults and 8 mL/kg for pediatric patients.

What drugs should you avoid during LAST?

During LAST, avoid: local anesthetics, beta-blockers, calcium channel blockers, and vasopressin. Use small-dose epinephrine (<1 mcg/kg) if needed for cardiac arrest. Benzodiazepines (midazolam) are first-line for seizures.

What are the early signs of local anesthetic toxicity?

Early CNS signs: metallic taste, perioral numbness, tinnitus, lightheadedness, confusion, slurred speech. Early cardiovascular signs: hypertension, tachycardia, palpitations. Important: neonates and infants under 6 months may present with sudden cardiovascular collapse WITHOUT prodromal CNS symptoms.

LAST Protocol

Local Anesthetic Systemic Toxicity — Treatment Guide

Based on ASRA 2020 Practice Advisory (Neal JM, et al. Reg Anesth Pain Med. 2020;45:247-253)

EMERGENCY REFERENCE. This is a clinical decision support tool. It does not replace clinical judgment. Call for help immediately if LAST is suspected. Have lipid emulsion (Intralipid 20%) immediately available before any regional anesthesia procedure.

Signs and Symptoms

CNS — Early

Metallic taste
Perioral numbness
Tinnitus (ringing in ears)
Lightheadedness
Confusion
Slurred speech

CNS — Late

Seizures
Loss of consciousness
Respiratory arrest

Cardiovascular — Early

Hypertension
Tachycardia
Palpitations

Cardiovascular — Late

Bradycardia
Hypotension
Wide-complex arrhythmias
Cardiac arrest

PEDIATRIC WARNING: Infants and neonates (<6 months) may present with sudden cardiovascular collapse WITHOUT prodromal CNS symptoms. Monitor closely.

Lipid Emulsion Dosing (Intralipid 20%)

Adult (≥70 kg) — Fixed Dose

Step	Dose	Rate
Bolus	100 mL	Over 2-3 minutes
Infusion	250 mL	Over 15-20 minutes
Max total	12 mL/kg

Adult (<70 kg) — Weight-Based

Step	Dose	Rate
Bolus	1.5 mL/kg	Over 2-3 minutes
Infusion	0.25 mL/kg/min	Continuous
Max total	12 mL/kg

Pediatric

Step	Dose	Rate
Bolus	1.5 mL/kg	Over 2-3 minutes
Infusion	0.25 mL/kg/min	Continuous
Max total	8 mL/kg (NOT 12)

PEDIATRIC MAX IS LOWER. Pediatric maximum lipid dose is 8 mL/kg, not the adult 12 mL/kg. Exceeding this limit risks fat overload syndrome.

If no clinical improvement after initial bolus, repeat bolus once. If still no response, increase infusion rate. May re-bolus every 3-5 minutes. Continue infusion for at least 15 minutes after hemodynamic stability.

Seizure Management

First line: Benzodiazepine (midazolam preferred)
If only propofol available: Low dose, 20 mg increments only
Avoid large propofol doses — they worsen cardiovascular depression
Secure airway — intubate if seizures persist
Start lipid emulsion immediately (do not wait for seizure control)

Cardiac Arrest Management

Epinephrine: <1 mcg/kg (small doses) — large doses worsen outcome
Start lipid emulsion immediately
Prolonged CPR may be needed — local anesthetics eventually redistribute
Consider cardiopulmonary bypass if available and arrest is refractory
Continue CPR and lipid for at least 60 minutes before considering termination

Key principle: Unlike other cardiac arrests, LAST-induced arrest is potentially reversible as drug redistributes from cardiac tissue. Prolonged resuscitation efforts are justified.

Drugs to Avoid During LAST

Drug Class	Reason
Local anesthetics	Worsens toxicity (obviously)
Beta-blockers	Worsen bradycardia and hypotension
Calcium channel blockers	Worsen cardiovascular depression
Vasopressin	Impairs lipid emulsion effectiveness

Prevention Strategies (PRAN Evidence)

Aspirate before injection — Check for intravascular placement
Incremental dosing — Inject in 3-5 mL aliquots, pausing 30-60 seconds between each
Calculate total dose before starting — Know the maximum for this patient before the first injection
Use ultrasound guidance — When available, reduces risk of intravascular injection
Use lowest effective concentration — Higher concentrations increase risk without improving block quality
Consider epinephrine test dose — 0.5 mcg/kg (max 15 mcg); positive if HR increases >10 bpm or BP increases >15 mmHg
Have lipid emulsion immediately available — Every location performing regional anesthesia must stock Intralipid 20%

Key Timers

Event	Duration
Lipid bolus administration	2-3 minutes
Lipid infusion	15-20 minutes
Pulse recheck during arrest	Every 2 minutes
Post-stability monitoring	Minimum 15 minutes
Observation after event	2 hours minimum; 12 hours if severe

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Related Dosing Guides

References

Neal JM, Barrington MJ, Fettiplace MR, et al. The Third ASRA Practice Advisory on Local Anesthetic Systemic Toxicity. Reg Anesth Pain Med. 2020;45(4):247-253.
Weinberg GL. Lipid emulsion infusion: resuscitation for local anesthetic and other drug overdose. Anesthesiology. 2012;117(1):180-187.
Rosenberg PH, Veering BT, Urmey WF. Maximum recommended doses of local anesthetics: a multifactorial concept. Reg Anesth Pain Med. 2004;29(6):564-575.

Clinical Decision Support Tool. This page is intended as a reference aid for licensed healthcare professionals only. It does not replace clinical judgment. Always verify information against current guidelines and institutional protocols.