Thursday Conference Content & EKG Review

Lidocaine Anesthetic Systemic Toxicity (LAST)

Dr. Carlos Cevallos, M.D.


Local anesthetics are a class of medications that includes esters and amides such as benzocaine/procaine and bupivacaine/lidocaine respectively

Local anesthetics MOA: Primarily through inhibition of voltage-gated sodium channels

Risk Factors for development of LAST:

  • High volume nerve blocks, lack of ultrasound guidance, prolonged high-dose lidocaine infusions, hepatic dysfunction, cardiac disease, renal disease, pregnancy

Clinical Presentation: Primarily affects the CNS and cardiovascular system

CNS: usually presents first

  • Sensory: tinnitus, perioral numbness, perioral numbness, metallic taste, blurred vision
  • Dizziness
  • Delirium
  • Tremors, lethargy
  • Dysarthria
  • Seizures
  • Respiratory depression

Cardiovascular symptoms:

  • Initial: Sympathetic activation (tachycardia, HTN, diaphoresis)
  • Late: Bradycardia, AV block, widened QRS, ventricular arrhythmias, PEA/Asystole


  • Immediately discontinue the anesthetic
  • Lipid Emulsion therapy:
    • Initial: 1.5ml/kg bolus of Intralipid 20% followed by infusion at 0.25ml/kg/min until 10 minutes after hemodynamic stability is obtained
    • If HD stability not obtained then you may re-dose the 1.5ml/kg bolus twice and increase the infusion to 0.5ml/kg/min
Friday Board Review

Board Review by Dr. Edward Guo

A 24 year old male with no past medical history presents to the ED for a snake bite. He collects snakes as a hobby, and his pet copperhead bit him on his left arm yesterday. Today, he woke up with pain and paresthesias over his left forearm. Vital signs are: Temp 99.8, HR 92, BP 132/90, RR 16, SpO2 98% RA. Exam shows two punctate lesions over the volar aspect of his forearm with mild surrounding erythema and no bleeding or drainage. There is a palpable radial pulse. The forearm is firm and tender to light palpation, and passive flexion of the wrist causes severe pain. 4 mg of IV morphine does not provide any relief. Which of the following is the next best step in management?

A: administer crotalidae polyvalent immune Fab

B: consult general surgery

C: mark surrounding area of erythema and monitor for progression

D: repeat another dose of 4 mg IV morphine

Answer: administer crotalidae polyvalent immune Fab

Compartment syndrome is a rare but known complication of snake bites. The first-line treatment of compartment syndrome in the setting of a snake bite is anti-venom as it is the effect of the venom on tissues that causes elevated compartment pressures. If compartment pressures continue to rise after administration of antivenom, consulting general surgery for a fasciotomy is a last resort intervention. Marking the lead edge of erythema and edema is wise to monitor for progression, but treatment of compartment syndrome should not be delayed. Another dose of IV morphine is not the definitive treatment for this condition.

Dart R.C., & White J (2020). Snakebite. Tintinalli J.E., & Ma O, & Yealy D.M., & Meckler G.D., & Stapczynski J, & Cline D.M., & Thomas S.H.(Eds.), Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 9e. McGraw Hill.