The impact of deep and moderate body temperatures on end-organ function during hypothermic circulatory arrest.

Objective: Hypothermic circulatory arrest (HCA) at different temperatures is a protection technique for operations involving the aortic arch. In combination with selective cerebral perfusion, higher arrest temperatures for the remaining body may be permitted. However, the ischaemic/reperfusion injury (I/R) in various organ systems, other than the brain, related to the specific HCA temperature has so far not been evaluated. Methods: Fourteen pigs were randomly assigned to 60 min of sole HCA at 20 or 30 8C temperature, weaned from cardiopulmonary bypass (CPB) and followed 4 h after HCA. Besides complex haemodynamic monitoring, laser-Doppler spectrophotometry for measuring capillary blood flow, tissue oxygen saturation and post-capillary venous filling pressures of the bowel was installed. At the end of experiment, organs were perfusion fixated and harvested. Results: During the entire experiment, haemodynamics revealed no differences between the groups. CPB bypass times were 177 12 min in the 20 8C and 158 11 min in the 30 8C group, respectively ( p = 0.02). During reperfusion, lactate levels were initially significantly higher in the 30 8C animals ( p = 0.001) but subsequently declined. Microcirculatory blood flow and velocity in the bowel were significantly reduced during cooling and reperfusion ( p < 0.05), but were independent of final HCA temperature. Histological evaluation revealed significantly more oedema formation in the bowel wall of the 30 8C animals ( p = 0.05). Conclusions: Higher levels of circulating lactate levels during reperfusion indicate less effective organ protection at 30 than at 20 8C after 60 min of HCA. This is further substantiated by histological evidence for a more pronounced oedema inflammatory response within the bowel wall. # 2011 European Association for Cardio-Thoracic Surgery. Published by Elsevier B.V. All rights reserved.