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    Local Anesthetic Dosing Calculator

    Doses local anesthetics to help avoid toxic doses.
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    IMPORTANT

    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.

    When to Use
    Pearls/Pitfalls
    Why Use

    Patients undergoing nerve blocks or regional anesthesia.

    • Toxicity is based on ideal body weight.

    • Local anesthetic systemic toxicity (LAST) is rare but potentially life-threatening. Symptoms can be divided into two main categories: 

      • Neurotoxicity: perioral numbness, metallic taste, mental status changes or anxiety, visual changes, muscle twitching, and ultimately, seizures, coma, and respiratory depression.

      • Cardiovascular toxicity: tachycardia, hypertension, ventricular arrhythmias, and/or asystole.

    • Patient risk factors for LAST include:

      • Extremes of age.

      • Decreased muscle mass.

      • Renal, hepatic, or cardiac disease.

      • Metabolic disturbances (acidosis, hypoxia, hypercarbia).

      • Pregnancy.

    • Procedural risk factors for LAST include:

      • Injection into highly vascular areas (highest incidence in paravertebral injections, followed by upper and lower extremity peripheral nerve blocks).

      • Multiple injections or infusion.

    • Ways to reduce risk of LAST:

      • Calculate patient’s maximum dose.

      • Dilution of anesthetic with normal saline allows for large volume blocks to be performed without risking toxic doses. 

      • Vasoconstrictors such as epinephrine can be added to decrease rate of absorption and therefore decrease toxic dose.

      • Use ultrasound to confirm needle placement.

      • Aspirate prior to injecting.

      • Monitor for development of symptoms.

    LAST can occur with any local anesthetic through any route of administration. Calculating the maximum dose in advance may help reduce risk.

    Bupivacaine
    Lidocaine
    Mepivacaine
    Ropivacaine
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    Result:

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    Next Steps
    Evidence

    Advice

    • If dose is above the threshold for toxicity, consider lowering the dose of local anesthetic.

    • 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.

    Management

    Diagnosing LAST:

    • 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.

    • 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:

    Critical Actions

    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.

    Content Contributors
    • Paul Hausknecht, MD
    Reviewed By
    • Nathan Teismann, MD
    Content Contributors
    • Paul Hausknecht, MD
    Reviewed By
    • Nathan Teismann, MD