Effects of Mild Perioperative Hypothermia on Cellular Immune Responses

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Abstract

Background

Unintentional perioperative hypothermia is a common complication of anesthesia and surgery associated with adverse effects on several systems, including impaired wound healing and more frequent wound infections. Mild hypothermia affects various immune functions. In the current study, the authors sought to determine whether immune alterations in the perioperative period might be induced, at least in part, by impaired thermoregulation during this period.

Methods

Sixty patients undergoing abdominal surgery were randomly assigned to two thermal care groups: routine care or forced-air warming. The patients' anesthetic care was standardized. Venous blood samples were collected 90 min before induction of anesthesia and immediately, 24 h, and 48 h after surgery. White cells were separated and frozen. Peripheral blood mononuclear cells were used to test cytokine production (interleukins [IL] -1 [small beta, Greek], -2, and -6; tumor necrosis factor-[small alpha, Greek] [TNF-[small alpha, Greek]), mitogens-induced proliferation, and natural killer NK cell cytotoxicity. Plasma cortisol levels were also determined.

Results

Patients in the normothermia group maintained normal body core temperature, whereas temperature decreased by approximately 1 [degree sign]C in the hypothermia group. Mitogenic responses were suppressed in cells from patients in the hypothermia but not in the normothermia group 24 and 48 h after surgery. Proinflammatory cytokine (IL-1 [small beta, Greek], IL-6, TNF-[small alpha, Greek]) production increased in both groups, although the production of IL-1 [small beta, Greek] was significantly higher in the normothermia group 24 h after surgery. Production of IL-2 was suppressed in the hypothermia but not in the normothermia group at 24 h.

Conclusions

Mild perioperative hypothermia suppressed mitogen-induced activation of lymphocytes and reduced the production of certain cytokines, IL-1 [small beta, Greek] and IL-2, and in this way may contribute to the immune alterations observed in the perioperative period.

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