Hyperthermia is an increase in temperature of 2 °C/h or 0.5 °C/15 min. It is uncommon for a patient to become hyperthermic based solely on maneuvers to conserve body heat in the operating room. Therefore, any increase in temperature must be investigated. Hyperthermia and its accompanying hypermetabolic state produce an increase in oxygen consumption, cardiac work, glucose demand, and compensatory minute ventilation. Sweating and vasodilation may result in decreased intravascular volume and venous return.