EFFECTS OF MILD PERIOPERATIVE HYPOTHERMIA ON CELLULAR IMMUNE-RESPONSES

Background: Unintentional perioperative hypothermia is a common compli cation of anesthesia and surgery associated with adverse effects on se veral systems, including impaired wound healing and more frequent woun d infections. Mild hypothermia affects various immune functions. In th e current study, the authors sought to determine whether immune altera tions in the perioperative period might be induced, at least in part, by impaired thermoregulation during this period.Methods: Sixty patient s undergoing abdominal surgery were randomly assigned to two thermal c are groups: routine care or forced-air warming. The patients' anesthet ic care was standardized. Venous blood samples were collected 90 min b efore induction of anesthesia and immediately, 24 h, and 48 h after su rgery. White cells were separated and frozen. Peripheral blood mononuc lear cells were used to test cytokine production (interleukins [IL] -1 beta, -2, and -6; tumor necrosis factor-alpha [TNF-alpha]), mitogens- induced proliferation, and natural killer NK cell cytotoxicity. Plasma cortisol levels were also determined. Results: Patients in the normot hermia group maintained nor mal body core temperature, whereas tempera ture decreased by approximately 1 degrees C in the hypothermia group. Mitogenic responses were suppressed in cells from patients in the hypo thermia but not in the normothermia group 24 and 48 h after surgery. P roinflammatory cytokine (IL-1 beta, IL-6, TNF-alpha) production increa sed in both groups, although the production of IL-1 beta was significa ntly higher in the normothermia group 24 h after surgery. Production o f IL-2 was suppressed in the hypothermia but not in the normothermia g roup at 24 h. Conclusions: Mild perioperative hypothermia suppressed m itogen-induced activation of lymphocytes and reduced the production of certain cytokines, IL-1 beta and IL-2, and in this way may contribute to the immune alterations observed in the perioperative period.