After induction of general anesthesia (without restriction as to type), the anesthesiologist will insert a temperature sensor into the distal esophagus. The distance will be determined by maximal heart sounds (if a stethoscope is used), or the probe will be inserted 0.48.(sitting height) - 4.4 cm. If an esophageal probe cannot be used, a thermometer can be inserted to between 10 and 20 cm into the nasopharynx. The surgical team will position a Foley catheter with temperature sensor into the urinary bladder. Ambient temperature will be recorded from an electronic probe situated at the height of the patients, well away from any heat-producing equipment.