Lidocaine-Induced Seizures: Mechanism and Prevention
Pathophysiology and Risk Factors
- The American College of Medical Toxicology suggests that lidocaine has an extremely narrow therapeutic window, with CNS toxicity beginning at plasma levels only slightly above therapeutic concentrations (>6 mcg/mL), and the mechanism involves concentration-dependent receptor blockade, affecting multiple receptor systems including Nav1.8/1.7, nicotinic cholinergic receptors, and voltage-gated calcium channels 1, 2
- The maximum safe dose is 4-4.4 mg/kg without epinephrine or 7 mg/kg with epinephrine, and exceeding these limits dramatically increases seizure risk 3
- Hepatic dysfunction, cardiac failure, cardiogenic shock, acidemia, hypoalbuminemia, and concurrent medications such as beta-blockers and amiodarone increase seizure risk even at therapeutic doses 1, 3
Clinical Manifestations and Management
- Early warning signs of lidocaine toxicity include perioral numbness, tinnitus, metallic taste, lightheadedness, and visual and auditory disturbances, which can progress to muscle twitching, slurred speech, confusion, tremors, and drowsiness 1, 3, 4
- Severe toxicity can lead to tonic-clonic seizures, respiratory depression and arrest, cardiovascular collapse, and loss of consciousness, requiring immediate treatment with discontinuation of lidocaine, airway management, seizure control with benzodiazepines, and intravenous lipid emulsion (ILE) 1, 3, 5