Local Anesthetic Dosing Calculator
Doses local anesthetics to help avoid toxic doses.
This calculator provides guidance for maximum dosing of local anesthetic and should not be used as the primary means of dosing. Always double check and err on the side of caution.
There is ongoing debate about which body weight measure best guides safe local anesthetic dosing.
- Some references use the patient’s actual body weight, which is generally appropriate for patients whose weight falls within a typical range.
- People at either end of the weight spectrum are more vulnerable to dosing errors.
- Professional bodies, such as the American Society of Regional Anesthesia and Pain Medicine (ASRA) and the Society for Obesity and Bariatric Anaesthesia (SOBA), advise dosing based on lean body weight (LBW), particularly for patients with obesity.
- Other resources, such as the British National Formulary (BNF) and the Association of Anaesthetists’ nomogram, use ideal body weight (IBW).
Regardless of the calculation method, clinicians should confirm that the final amount remains below the agent’s published maximum dose and remain vigilant for local anesthetic systemic toxicity.
Note: Previous versions of Goldfrank’s reported an increased maximum allowable dosage due to the vasoconstrictive effects of epinephrine when added to local anesthetics. The most recent version no longer includes this adjustment. While there likely is a higher safe dose when epinephrine is added, we no longer include that estimate on this calculator, and as always, dosages should be double-checked and reviewed using your local pharmacy and policies.
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If dose is above the threshold for toxicity, consider lowering the dose of local anesthetic.
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Prepare for adverse events by storing a checklist for management as well as intralipid in a nerve block cart (does not require refrigeration) for easy access if any complications should occur.
Diagnosing LAST:
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Local anesthetic toxicity results from sodium channel blockade, which affects the central nervous system and cardiac system. The CNS is more sensitive to the effects of local anesthetics than the cardiac system and will generally manifest signs/symptoms of toxicity first.
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The presenting symptoms of LAST include perioral numbness, metallic taste, mental status changes or anxiety, visual changes, muscle twitching, and ultimately, seizures, coma, and respiratory depression. Cardiovascular effects include tachycardia, hypertension, ventricular arrhythmias and/or asystole.
Management of LAST:
- Stop the infusion.
- Provide supportive care (advanced cardiovascular life support, benzodiazepines for seizures, airway management).
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Consider giving intralipid (see guidelines: American Society of Regional Anesthesia and Pain Medicine, Association of Anaesthetists of Great Britain and Ireland).
Multiple variables may influence a patient's risk of developing LAST. This weight based calculator should be used to generate a rough estimate for toxic doses.