Impact of hypothermia on the immunologic response after trauma and elective surgery.

An Hypothermia is defined as a decrease in core temperature below 35 degrees C. The well-described deleterious effects of accidental hypothermia on outcome in multiple-trauma patients contrast the beneficial effect of controlled hypothermia on organ function during ischemia in elective surgery. Experimental studies have shown that induced hypothermia during hemorrhagic shock might have beneficial effects on outcome. The beneficial effects of induced hypothermia appear to be partly mediated by the prolongation of the "golden hour" with prevention of hypoxic organ dysfunction. However, hypothermia also has been thought to have an impact on the immunologic response after trauma and elective surgery. Induction of hypothermia seems to decrease the release of pro-inflammatory cytokines believed to influence distant organ damage positively, and is mediated by the interaction of polymorphonuclear leucocytes (PMNL) and capillary endothelial cells. Nevertheless, the incidence of posttraumatic infectious complications may be increased after induction of hypothermia due to an overexpression of anti-inflammatory cytokines. Together with this immunosuppressive profile, coagulopathy and bleeding might limit the use of induced hypothermia after multiple trauma and elective surgery. The purpose of this Chapter is to highlight current knowledge regarding the interaction of hypothermia and posttraumatic immune reactivity. A better understanding of these mechanisms would assist the introduction of preventive and therapeutic strategies into clinical practice.