Local Anaesthetic Max Dose & LAST

Dosing weight

Every milligram on this page is multiplied by this weight.

Weight used— kg

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In obesity the dose is calculated on lean body weight — Nightingale et al, Anaesthesia 2015;70:859–876 (AAGBI / SOBA): it is safer to calculate local anaesthetic dose using lean body weight. Lean body weight equation: Janmahasatian et al, Clin Pharmacokinet 2005;44:1051.

Agent

Lidocaine — single-shot maximum

Two sources per agent. Where they disagree the range is shown; act on the lower figure.

Maximum—

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For this patient— mg

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With adrenaline—

Volume at each concentration

ml = maximum mg ÷ (concentration % × 10 mg/ml)

Site of injection changes the peak plasma level far more than the milligram total does — intercostal > caudal > epidural > brachial plexus > subcutaneous for the same dose. A single number cannot be safe for every block: Rosenberg, Veering & Urmey, Reg Anesth Pain Med 2004;29:564–575.

Mixture — cumulative load

Toxicity is additive across agents, so the fractions add, not the milligrams.

Combined share of maximum— %

Add an agent and a volume

Each fraction is measured against the lower, more conservative end of that agent's range. Volumes already given from the surgical field count too.

Additivity: Rosenberg, Veering & Urmey, Reg Anesth Pain Med 2004;29:564–575 — the toxicity of the amide-linked local anaesthetics is additive. ASRA LAST checklist, 2020 version (Neal, Neal & Weinberg, Reg Anesth Pain Med 2021;46:81–82) — avoid giving other local anaesthetics once toxicity is suspected.

LAST rescue — 20 % lipid emulsion

Stop injecting. Call for help and for the lipid rescue kit. 100 % oxygen, no hyperventilation.

Bolus · 1.5 ml/kg— ml

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Infusion · 15 ml/kg/h— ml/h

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If still unstable · doubled— ml/h

After 5 min: up to two repeat boluses at the same dose, 5 min apart, three boluses in total — and double the infusion rate at any time if circulation has not been restored or deteriorates.

Maximum cumulative · 12 ml/kg— ml

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Adrenaline bolus · ≤ 1 µg/kg— µg

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Avoid vasopressin, calcium channel blockers, beta blockers and any further local anaesthetic. Lidocaine must not be used as an antiarrhythmic here. Avoid large doses of propofol, especially if haemodynamically unstable — propofol is not a substitute for lipid emulsion.

Seizures: a benzodiazepine is preferred. If pulseless, start CPR and continue it throughout lipid treatment — recovery from local-anaesthetic cardiac arrest may take more than an hour, and arrhythmias may be refractory. Alert the nearest cardiopulmonary bypass team early. Monitor at least 4–6 h after a cardiovascular event, at least 2 h after a limited CNS event.

ASRA Local Anesthetic Systemic Toxicity checklist, 2020 version — Neal JM, Neal EJ, Weinberg GL, Reg Anesth Pain Med 2021;46:81–82 (doi:10.1136/rapm-2020-101986); dosing detail as set out in Neal, Woodward & Harrison, Reg Anesth Pain Med 2018;43:150–153. AAGBI Safety Guideline, Management of Severe Local Anaesthetic Toxicity, 2010, endorsed by ANZCA. The two agree on 1.5 ml/kg, 15 ml/kg/h (≡ 0.25 ml/kg/min), doubling to 30 ml/kg/h and a 12 ml/kg ceiling; they differ on bolus time (1 min AAGBI, 2–3 min ASRA) and on the fixed regimen above 70 kg. Lipid emulsion for LAST is an off-label use.