Can lidocaine (local anesthetic) cause seizures?

Lidocaine Can Cause Seizures: Mechanisms, Risk Factors, and Management

Yes, lidocaine can cause seizures as a manifestation of central nervous system toxicity, particularly at high plasma concentrations or in susceptible individuals. 1

Mechanism of Lidocaine-Induced Seizures

• Lidocaine has a concentration-dependent effect on seizures - at lower concentrations it has anticonvulsant properties, but at concentrations above 15 μg/mL, it frequently results in seizures 2
• Seizures are part of the excitatory manifestations of central nervous system toxicity, which can occur before depressant effects 1
• In experimental models, lidocaine-induced seizures invariably start in the amygdala, though in clinical practice they typically present as generalized seizures 2

Clinical Manifestations of Lidocaine Toxicity

• Early warning signs of CNS toxicity include restlessness, anxiety, tinnitus, dizziness, blurred vision, tremors, and muscle twitching 1
• Progression of toxicity can lead to confusion, slurred speech, and seizures 3
• Advanced toxicity may result in respiratory depression, unconsciousness, and cardiovascular collapse 1
• Seizures are typically generalized tonic-clonic in nature 4, 5

Risk Factors for Lidocaine-Induced Seizures

• Excessive dosage exceeding recommended limits (maximum dose with epinephrine: 7 mg/kg; without epinephrine: 4-4.4 mg/kg) 6
• Rapid absorption or inadvertent intravascular injection 1
• Hepatic dysfunction (impaired metabolism of lidocaine) 1
• Cardiac failure (extends half-life to >4 hours) 3
• Cardiogenic shock (extends half-life to >20 hours) 3
• Acidemia (increases free lidocaine concentration) 3
• Hypoalbuminemia (increases free drug in plasma) 3
• Concurrent use of medications that reduce lidocaine metabolism (e.g., beta-blockers, amiodarone) 3
• Prolonged infusions exceeding 12 hours (non-linear pharmacokinetics with accumulation) 3

Timing of Seizure Occurrence

• Seizures can occur immediately after rapid IV administration 3
• Delayed seizures may occur up to 3.5 hours after administration, particularly with topical application to mucosal surfaces 7
• For bronchoscopy procedures using lidocaine instillation, delayed toxicity has been reported due to slow absorption from the bronchial tree 7, 8

Prevention of Lidocaine-Induced Seizures

• Use the lowest effective dose 1
• For infusions lasting >12 hours, reduce the rate by approximately 50% at 12-24 hours 3
• Use ideal body weight rather than actual body weight for dose calculations in patients with high BMI 3
• Monitor plasma levels when infusions continue beyond 24 hours 3
• Avoid applying excessive doses to mucosal surfaces where systemic uptake can occur 6
• Exercise caution in patients with hepatic disease, impaired cardiovascular function, or advanced age 1
• Have resuscitative equipment, oxygen, and emergency drugs immediately available 1

Management of Lidocaine-Induced Seizures

• Immediate discontinuation of lidocaine administration 3
• Airway management and ventilation with 100% oxygen 6
• Seizure control with benzodiazepines (e.g., intravenous midazolam 0.1-0.2 mg/kg) 6
• Avoid propofol if cardiovascular instability is present 6
• For severe toxicity from amide local anesthetics, administer 20% lipid emulsion (1.5 mL/kg over ~1 minute) 6
• Continue monitoring for recurrent seizures, as they may occur even hours after the initial event 7

Case Examples

• A 4-year-old boy developed recurrent tonic-clonic seizures after accidental ingestion of lidocaine 2% solution 4
• A 17-month-old developed grand mal seizures during cardiac catheterization after receiving 38 mg/kg of lidocaine (9 times the recommended maximum dose) 5
• A patient experienced delayed tonic-clonic seizures 3.5 hours after lidocaine instillation during bronchoscopy, with plasma levels in the toxic range (18.32 μg/mL) 7

Recognizing the potential for lidocaine to cause seizures is essential for clinicians using this medication. Proper dosing, careful administration techniques, and vigilant monitoring can help prevent this serious adverse effect, especially in high-risk patients.