Heat Loss from Patients during Anesthesia

Abstract

Constant body temperature in an unanesthetized human is due to thermoregulatory system activity. In thermoneutral and warm environments, sweating and cutaneous vaso-activity both influence heat loss from the body surface. In a cold environment, shivering increases metabolic heat production. Shivering does not often occur during anesthesia because of the use of muscle relaxants. The basal metabolic rate during surgery can also be lowered by the anesthetic agents which suppress oxidative metabolism.¹ Most anesthetics (halothane, nitrous oxide) produce vasodilatation.² This is followed by a rise in the skin temperature and increased heat loss from the body. The latter effect can be associated with a considerable decrease in the central body temperature. As the compensatory mechanisms are impaired during anesthesia, physical environmental conditions are most important in governing the heat exchange between patients and their surroundings.