Local Anesthetic Maximum Dose Calculator

2 mg/kg, up to 150 mg as a single dose, which is the limit in the product licence (SmPC); the calculator applies it with or without adrenaline. In adults with a BMI of 30 or more it uses lean body weight. A 0.5% solution contains 5 mg/mL, so 150 mg is 30 mL of 0.5% or 60 mL of 0.25%. This is a reference ceiling, not a volume that is safe for every block: the licence gives smaller doses for many techniques.

About 3 mg/kg is a common guide, and the calculator caps it at 225 mg. The product licence gives dose ranges by block rather than a single maximum, for example 225–300 mg of 7.5 mg/mL for a brachial plexus block. Ropivacaine 0.2% contains 2 mg/mL and 0.75% contains 7.5 mg/mL.

Multiply the percentage by 10: 1% is 10 mg/mL, 2% is 20 mg/mL and 0.5% is 5 mg/mL. Divide the maximum dose in mg by the mg/mL to get the volume that contains it: 200 mg of lidocaine is 20 mL of 1%. That volume is an arithmetic equivalent, not a volume that is safe to inject in every block.

20% lipid emulsion: a bolus of 1.5 mL/kg over 2 to 3 minutes, then an infusion of 15 mL/kg/h. Repeat the bolus at 5 and 10 minutes if needed, and double the infusion to 30 mL/kg/h if the patient is still unstable. Do not exceed 12 mL/kg in total (Association of Anaesthetists QRH 3-10, June 2023). Lipid is one part of the QRH 3-10 algorithm: stop injecting, call for help, secure the airway and treat seizures and arrhythmias as well.

Most of the extra weight in obesity is fat, which takes up little local anaesthetic at first, so a dose on total body weight can give toxic plasma levels. The calculator uses lean body weight for adults with a BMI of 30 or more, as the Association of Anaesthetists and SOBA guidance (2015) recommends.