Local Anesthetic Toxicity, Treatment Checklist.



    


    Local anesthetic toxicity (LAST) can occur because of inadvertent intravascular injection or dosing error. Intravascular injection can cause toxicity even if the anesthetic was administered within the recommended dose range.


     Consider LAST in any patient with altered mental status, neurological symptoms or cardiovascular instability following a regional anesthetic.

  • Central nervous system signs (may be subtle or absent) 

    • Excitation (agitation, confusion, muscle twitching, seizure) 

    • Depression (drowsiness, obtundation, coma or apnea) 

    • Non-specific (metallic taste, circumoral numbness, diplopia, tinnitus, dizziness)

  • Cardiovascular signs (often the only manifestation of severe LAST)

  • Initially may be hyperdynamic (hypertension, tachycardia, ventricular arrhythmias), then 

  • Progressive hypotension 

  • Conduction block, bradycardia or asystole 

  • Ventricular arrhythmia (ventricular tachycardia, Torsades de Pointes, ventricular fibrillation) 

  • Sedative hypnotic drugs reduce seizure risk but even light sedation may abolish the patient’s ability to recognize or report symptoms of rising LA concentrations.


Treatment of Local Anesthetic Systemic Toxicity (LAST):

  • Get Help

  • Initial Focus

    • Airway management: ventilate with 100% oxygen

    • Seizure suppression: benzodiazepines are preferred; AVOID propofol in patients having signs of cardiovascular instability

    • Alert the nearest facility having cardiopulmonary bypass capability

  • Management of Cardiac Arrhythmias

    • Basic and Advanced Cardiac Life Support (ACLS) will require adjustment of medications and perhaps prolonged effort

    • AVOID vasopressin, calcium channel blockers, beta blockers, or local anesthetic

    • REDUCE individual epinephrine doses to < 1 mcg/kg

  • Lipid Emulsion (20%) Therapy (values in parenthesis are for 70kg patient)

    • Bolus 1.5 mL/kg (lean body mass) intravenously over 1 minute (~100mL)

    • Continuous infusion 0.25 mL/kg/min (~18 mL/min; adjust by roller clamp)

    • Repeat bolus once or twice for persistent cardiovascular collapse

    • Double the infusion rate to 0.5 mL/kg/min if blood pressure remains low

    • Continue infusion for at least 10 minutes after attaining circulatory stability

    • Recommended upper limit: Approximately 10 mL/kg lipid emulsion over the first 30 minutes



RISK REDUCTION (BE SENSIBLE) 

  • Use the least dose of LA necessary to achieve the desired extent and duration of block. 

  • Local anesthetic blood levels are infl uenced by site and of injection and dose. Factors that can increase the likelihood of LAST include: advanced age, heart failure, ischemic heart disease, conduction abnormalities, metabolic (e.g., mitochondrial) disease, liver disease, low plasma protein concentration, metabolic or respiratory acidosis, medications that inhibit sodium channels. Patients with severe cardiac dysfunction, particularly very low ejection fraction, are more sensitive to LAST and also more prone to ‘stacked’ injections (with resulting elevated LA tissue concentrations) due to slowed circulation time. 

  • Consider using a pharmacologic marker and/or test dose, e.g. epinephrine 5 mcg/mL of LA. Know the expected response, onset, duration, and limitations of “test dose” in identifying intravascular injection.

  •  Aspirate the syringe prior to each injection while observing for blood.

  •  Inject incrementally, while observing for signs and querying for symptoms of toxicity between each injection. 

Source: www.asra.com

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