[Etiology and sequelae of perioperative accidental hypothermia]

Accidental hypothermia is a frequent event during the perioperative period. Recent studies revealed a drop in core temperature of over 2 degrees C in more than 50% of all patients undergoing an operation. This drop in core temperature seems to be primarily due to the following factors. Anaesthesia prevents behavioural adaptations to changes in ambient temperature. Simultaneously, autonomic mechanisms of temperature control are suppressed by general as well as by neuraxial anaesthesia. The interthreshold range between core temperatures that trigger responses to warmth and to cold increases up to 20-fold. This is primarily due to a decrease in the cold response threshold. As a result, body core temperature of anaesthetized patients is primarily determined by the much lower temperature of the environment. On one hand, decreases in body temperatures may exert organ protective effects under certain conditions, e.g., by increasing ischemic tolerance. On the other hand, there is accumulating evidence that accidental perioperative hypothermia may also adversely affect organ function and outcome. For example, unfavourable effects of perioperative hypothermia on the immune defence, on the function of the coagulation system, on cardiovascular performance, as well as on postoperative recovery have been reported. Consequently, measures should be taken to actively control the perioperative heat balance of patients.