Fever versus hyperthermia.

A variety of conditions that result in the elevation of body temperature are described and discussed. These hyperthermias are divided into four categories; fever, exercise hyperthermia, hyperthermias due to inadequate means of heat dissipation, and hyperthermias resulting from pathological or pharmacological impairments of thermoregulatory mechanisms. A comparison of the physical and physiological characteristics of these hyperthermias is presented and distinctions are drawn on the basis of these characteristics. Fever is shown to differ markedly from all other forms of hyperthermias. Specifically, the elevation in body temperature encountered during fever is a regulated rise that is defended by fully functional thermoregulatory mechanisms; the thermopreferendum is also elevated in fever, particularly at the onset or "chill phase"; and aspirin-like drugs can intervene in febrile hyperthermia and will return body temperature to its normal level. No other forms of hyperthermia possess these characteristics and thus only fever can be attributed to an upward displacement of the "set point" for body temperature regulation. Furthermore, in attempting to control rises in body temperature, it is apparent that aspirin is effective only in fever, while whole-body cooling is all but ineffective. In all other forms of hyperthermia, whole-body cooling is the only effective treatment.