Systemic Toxicity of Local Anesthetics - how a simple laceration repair can go wrong 

Mechanism of action of local anesthetics - sodium channel blockade inhibits propagation of nerve impulses

Toxicity occurs due to systemic effects of meds in a dose-related fashion 

• Longer acting = higher risk of systemic toxicity (bupivacaine > lidocaine)
• Dosage limits of common agents:
• Lidocaine - 4mg/kg vs 7mg/kg with epinephrine
• Bupivacaine - 3mg/kg vs 5mg/kg with epinephrine

Signs and symptoms of toxicity:

• Vague neuro symptoms - tongue numbness, lightheadedness, visual and auditory hallucinations, twitching
• Can progress to refractory seizures ​and cardiovascular collapse 
• Usually occurs within minutes of injection

Management

• ABC’s 
• Benzodiazepines for seizures
• IV 20% lipid emulsion - 1.5mL/kg over 1 min then w/ continuous infusion/repeat dosage every 3 min until improved clinically (max of 10mL/kg over 30min); dosage variable depending on source referenced

Prevention

• Calculate dose limits, especially if repair of large/many lacerations or if performing larger volume regional block
• Always aspirate prior to infiltration of anesthetic agent to avoid injecting directly into vasculature.

Dillon, D, Gibbs, M. “Local and Regional Anesthesia.” Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 8eEds. Judith E. Tintinalli, et al. New York, NY: McGraw-Hill, 2016.