Figure 1. Electrocardiography (EKG) changes observed in lead II (top) 45 min after incision. Is this a sudden onset of supraventricular tachycardia or interference from the dermatomal-sensory-evoked-potential monitoring? The EKG trace in lead V⁵(bottom) shows the more frequent interference pattern we observed during previous somatosensory-evoked-potential monitoring.