Methohexital-Induced Seizure in a Patient Undergoing Conscious Sedation

Background: Methohexital is a short-acting barbiturate used for procedural sedation in the emergency department (ED). As with other sedatives, adverse effects with methohexital include excess sedation and hypotension, but this agent can also lower the seizure threshold. We report a patient who developed a generalized seizure after administration of methohexital.

Case report: A 60-year-old man presented to the ED by ambulance with chest pain and shortness of breath. Paramedics had administered adenosine for supraventricular tachycardia without conversion before arrival to the ED. He had no history of seizures. His initial vital signs in the ED included heart rate of 189 beats/min with a supraventricular rhythm, blood pressure 137/108 mm Hg, respiration 22 breaths/min, and oxygen saturation of 98% on room air. It was decided to attempt synchronized electrical cardioversion, and methohexital 1 mg/kg (120 mg) was administered over 2 min for moderate sedation. Within 15 s of methohexital administration, the patient developed a generalized seizure that lasted for 90 s. After seizure termination, he was successfully cardioverted, returned to his previous baseline level of consciousness within 20 min, and discharged without further problems with a follow-up referral to neurology. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Methohexital is a short-acting barbiturate used for moderate sedation. Its adverse effects are unique in that it can lower the seizure threshold in some patients. Alternative agents for sedation should be considered in individuals with possible seizure disorders.

Keywords: barbiturates; convulsions; methohexital; seizures; toxicity.