fever [L, febris] , an elevation of body temperature above the normal circadian range as a result of an increase in the body’s core temperature. Fever is a temperature above 37.2° C (98.9° F) in the morning or above 37.7° C (99.9° F) in the evening. Fever results from an imbalance between the elimination and the production of heat. Exercise, anxiety, and dehydration may increase the temperature of healthy people. Infection, neurological disease, malignancy, pernicious anemia, thromboembolic disease, paroxysmal tachycardia, congestive heart failure, crushing injury, severe trauma, and many drugs may cause fever. No single theory explains the mechanism whereby the temperature is increased. Fever has no recognized function in conditions other than infection. It increases metabolic activity by 7% per degree Celsius, requiring a greater intake of food. Convulsions may occur in children whose fevers tend to rise abruptly, and delirium is seen with high fevers in adults and in children. Very high temperatures, as in heatstroke, may be fatal. The course of a fever varies with the cause, the condition of the patient, and the treatment given. The onset may be abrupt or gradual, and the period of maximum elevation, called the stadium or fastigium, may last for a few days or up to 3 weeks. The fever may resolve suddenly, by crisis, or gradually, by lysis. Certain diseases and conditions are associated with fevers that begin, rise, and fall in such characteristic curves that diagnosis may be made by studying a graphic record of the course of the fever. Also called febrile response. Kinds include habitual fever, intermittent fever, relapsing fever. See also fever treatment, hyperpyrexia, quartan malaria, remittent fever, septic fever, tertian malaria.
