Whether the iThermonitor is sufficiently accurate for clinical use remains unknown. The investigators thus propose to evaluate the system in perioperative patients who often experience thermal perturbations over a range of several °C. Specifically, the investigators propose to determine the precision and accuracy of iThermonitor in surgical patients and during the initial hour of recovery. As in previous studies, the investigators will consider the thermometer sufficiently accurate for clinical use if most Raiing temperatures are within ±0.5°C of the reference temperature.