Hyperthermia in ICU patients

Abstract

Thermoregulation is the ability of an organism to keep its body temperature within certain limits, even when the surrounding temperature is very different. If the body is unable to maintain a normal temperature and its temperature significantly increases above normal, a condition known as hyperthermia ensues. Although an elevated body temperature usually represents a fever in the vast majority of patients, there are a few occasions in which an elevated temperature is secondary to hyperthermia: heat stroke syndromes, certain metabolic diseases (hyperthyroidism), and use of drugs that interfere with thermoregulation. Both hyperthermia and fever result in an elevation of body temperature, but they differ physiologically. With fever, thermoregulatory mechanisms remain intact, but the hypothalamic thermal set point is raised by exposure to endogenous pyrogens, leading to behavioral and physiologic responses to elevate body temperature. In contrast to fever, during hyperthermia, the setting of the thermoregulatory center remains unchanged at normothermic levels, whereas body temperature increases in an uncontrolled fashion and overrides the ability to lose heat.