New onset fever in the intensive care unit.

Fever is defined as a core body temperature of >38.3 degrees C or 101 degrees F. About 50% of fevers in the ICU are due to infectious causes. Absence of fever in patients with infection heralds a poor prognosis. Temperatures between 102 degrees F-106 degrees F are more likely to be due to infection. The common infectious causes of fever are pneumonia, urosepsis, line infections and intraabdominal infections. Temperatures <102 degrees F or >106 degrees F are usually due to non-infectious causes like deep venous thrombosis, infusion reactions, aspiration, drug fever and the neuroleptic malignant syndrome. Fever should be distinguished from hyperthermia as antipyretics are ineffective in the latter. Inappropriate use of antibiotics selects resistant bacterial strains, but delay in treating infection could increase mortality. A structured approach is therefore required in order to correctly diagnose and treat fever in critically ill patients.