Asystole During Administration of Dexmedetomidine with Spinal Anesthesia: A Case Report

Abstract

Dexmedetomidine is a useful sedative drug that does not cause severe respiratory depression but sometimes causes hypotension or bradycardia. We encountered a case in which asystole occurred during transurethral lithotomy (TUL) that was performed under spinal anesthesia with administration of dexmedetomidine. The patient was a 73-year-old man whose medical history included radiation therapy for prostate cancer and TUL, which had been performed under spinal anesthesia without incident. Results of preoperative examination were unremarkable, and electrocardiography (ECG) showed sinus rhythm with heart rate of 74 bpm. Spinal anesthesia was administered with 3.4 mL of 0.5% hyperbaric bupivacaine, and upper level sensory loss was confirmed at T10. Ten minutes after injection of the bupivacaine, dexmedetomidine was administered for sedation at a loading dose of 3 μg/kg/h over 10 minutes; it was continued at 0.4 μg/kg/h. The patient’s vital signs were stable, but because his SpO₂ on room air decreased to 93%, oxygen inhalation was started, and the dexmedetomidine was reduced to 0.2 μg/kg/h. Upon completion of the operation, 115 minutes after the bupivacaine injection, the patient groaned, and almost simultaneously, his heart rate decreased to 30 bpm and progressed to asystole. The dexmedetomidine infusion was stopped, and 0.5 mg of atropine was injected intravenously. Before chest compressions were started, sinus rhythm returned, and the patient regained consciousness. No ECG abnormalities were found. Upper level sensory block at T10 was reconfirmed. The patient was discharged the next day without complications. We reasoned that the asystole resulted as an adverse effect of the dexmedetomidine, from a vagal reflex, and from the spinal anesthesia. Our case illustrates both the importance of avoiding the administration of dexmedetomidine above the recommended dose during spinal anesthesia and the need for careful ECG monitoring and observation of hemodynamics in patients undergoing TUL.