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