Somatosensory-evoked-potential technique is widely used for perioperative monitoring. We present a case of a 68-year-old woman who had sinus arret during electrical stimulation in her lower extremity for somatosensory evoked potentials. She underwent laminoplasty for cervical spondylotic myelopathy, anesthetized by propofol, fentanyl, sevoflurane, and nitrous oxide. After intubation and prone position setting, her bilateral tibial nerves were stimulated (50mA for 0.3 msec, 4Hz) . Sinus arrest occured right after stimulation started, and disappeared immediately after stimulation ceased. This phenomenon was seen even after atropine injection. Since no cardiovascular factors that can contribute to sinus arrest were present, the combination of anesthetic agents, prone position, and somatosympathetic reflex induced by tibial nerve stimulation are likely to have been responsible.
