Perioperative fever.

Unlike normal thermoregulatory control, which is largely neuronally mediated, fever is activated by circulating pyrogens. Pyrogens are triggered by either infectious or non-infectious etiologies, all of which may be present in patients undergoing ambulatory surgery. Fever is a regulated elevation in the setpoint temperature for all thermoregulatory responses (warm and cold defenses). To increase core temperature according to the newly elevated setpoint, cold defenses such as vasoconstriction and shivering are activated. In contrast, anesthesia widens the interthreshold range, thus resulting in hypothermia. As a result, general anesthesia impairs the febrile response to pyrogenic stimulation. However, the precise nature of the interaction between fever and anesthesia has yet to be determined. Postoperative fever continues to be a major problem. Wound infections are responsible for many such fevers, although numerous other etiologies contribute. Initial diagnosis should thus focus on determining the etiology of fever. Once that is established, treatment can focus on the specific cause.