Impaired Thermoregulation and Perioperative Hypothermia in the Elderly

Body temperature is normally maintained within very narrow limits by the smoothly coordinated functioning of a system consisting of afferent, central and efferent parts. The sometimes extreme physiologic adjustments necessary to accomplish this will occur even at the expense of circulatory integrity. Any or all parts of the thermoregulatory system can be impaired by either drugs or by age. In general, elderly patients are likely to have both decreased heat production and a lessened ability to prevent heat loss. This makes them especially likely to sustain drops in body temperature during anesthesia and operation. Intraoperatively, accidental hypothermia can cause a relative overdose and prolongation of anesthesia as well as other problems. In the recovery period, residual hypothermia is more likely to be dangerous in the elderly patient both because of prolonged time to awakening and mobility, and because the increased oxygen demand caused by shivering may not be supportable by diminished cardiovascular and respiratory function.