Effects of Hypothermia on Blood Endogenous Endotoxin Levels During Cardiopulmonary Bypass

Endotoxins activate white blood cells and complement and produce a spectrum of clinical syndromes ranging from fever to septic shock. Although, production of endogenous endotoxemia during cardiopulmonary bypass (CPB) has recently been reported, the role of hypothermia on endotoxemia is not clear. In this study, we evaluated the effects of moderate (24-28°C) and mild (32-34°C) hypothermia on blood endotoxin levels. The study population consisted of 20 patients who underwent CABG with CPB. Moderate hypothermia was applied during aortic crossclamping in 10 patients (Group 1) and mild hypothermia was applied in the remaining 10 patients (Group 2). The mean rectal temperatures were 26,8 ± 1,2 °C in Group 1 and 33,8 ± 0,8° C in Group 2. Blood samples for endotoxin level measurements were obtained before CPB, during aortic crossclamping, immediately and 20 minutes after the release of the cross-clamp, after CPB and 24 hours postoperatively. Endotoxins were absent in any of the samples before CPB, but were detected after CPB in both groups. The endotoxin levels were significantly higher in Group 1 than in Group 2. Endotoxin levels become higher when hypothermia gets deeper, probably due to intestinal ischemia. The present study suggests that when hypothermia is the technique of choice, the deleterious effects of endotoxemia on patients with poor conditions must be considered.