[Fever in critically ill patients: frequent causes, diagnostic procedures, and therapy]

Fever is an adaptive physiological process. In reaction to specific proteins (pyrogens) distributed by the blood the reference temperature increases, thus the organism has to produce heat. In intensive care units approximately 50 percent of fever episodes are caused by hospital acquired infections, while other episodes result from non-infectious diseases or their aetiology remain undetected. A special kind of fever is the hyperthermia following malfunctioning hypothalamic regulation after central nervous diseases or injuries. In patients with severe head injuries any increase of temperature has to be prevented as hyperthermia is associated with more adverse outcomes. If the hyperthermia can be attributed to other aetiological factors, a decrease of temperature is not desirable provided that the consequences of fever do not jeopardize the patient for further health risks. As a basis of therapy, the aetiology of fever episodes should be diagnosed taking recent scientific knowledge and guidelines into consideration. The most reliable temperature values are measured by using invasive sensors, particularly in pulmonary arterial catheters or bladder catheters. Alternatively usual thermometers can be applied, due to unreliable results excepting in the axilla.