Fig. 1. Time course of mean arterial pressure, MN-SSEP amplitude, esophageal temperature, and heart rate during anesthesia and surgery in a patient undergoing resection of a choroidal melanoma delineating the two episodes of evoked arterial hypotension in their relation to body temperature. A similar time course was observed in other patients except for variation in the duration of the final stage of tumor resection. Values of variables during hypotension before and during hypothermia were compared 15 min after hypotension had been achieved. Hypotension with a mean arterial pressure of 40 mmHg lasted approximately 20 min before hypothermia and averaged approximately 60 min during hypothermia of 32°C. Heart rate continuously decreased as esophageal temperature decreased from 36.1°C to 31.9°C.