Perioperative thermoregulation and heat balance.

In summary, both regional and general anesthesia markedly impair the normal precise regulation of core body temperature. Consequently, inadvertent perioperative hypothermia is common. Hypothermia develops because the typical operating room environment is cold; however, it is anesthetic-induced impairment of thermoregulatory responses that contributes most. Internal redistribution of body heat is a surprisingly important factor, contributing more to core hypothermia than net heat loss in most patients. There is now convincing evidence that a typical amount of intraoperative hypothermia, say 2 degrees C, predisposes numerous complications and alters patient outcome. Fortunately, effective methods are available for preventing hypothermia.