Local anesthetic systemic toxicity

Local Anesthetic Systemic Toxicity (LAST)

• More vascular injection sites, dose, the local anesthetic's intrinsic pharmacokinetic properties, and the addition of a vasoactive agent all affect the risk for LAST
• CNS toxicity:
  • Local anesthetics readily cross the blood brain barrier
  • Clinical manifestations: lightheadedness, tinnitus, tongue numbness, metallic taste → CNS excitation (block inhibitory pathways) → CNS depression, seizure → coma
• Cardiovascular toxicity
  • Dose dependent blockade of Na channels → disruptions of cardiac conduction system → bradycardia, ventricular dysrhythmias, decreased contractility, cardiovascular collapse/circulatory arrest
  • Bupivacaine has higher risk of CV toxicity
  • Approximately 3x the amount of local anesthetics are required to produce cardiovascular toxicity than CNS toxicity
  • Addition of epi allows for early detection of intravascular injection and also increases the max allowable dose
• Treatment of LAST:
  • Initial management:
    • Call for intralipid kit
    • ABCs: do you need to support circulation/airway?
    • Stop local anesthetic
    • Give benzodiazepines for seizure
    • Reduce individual epinephrine doses to <1 mcg/kg
    • AVOID: vasopressin, Ca channel blockers, Beta blockers, local anesthetics, and propofol (can further decrease cardiac contractility)
  • Initiate early intralipid (IL) therapy
    • Rapidly give 1.5 cc/kg bolus of 20% intralipid IV (*max 3 doses)
    • Start infusion at 0.25 cc/kg/min (*max rate 0.5 cc/kg/min)
    • If patient remains unstable, may repeat bolus and increase infusion rate