Ischemic Postconditioning Attenuates Lung Ischemic/Reperfusion Injury Induced By Cardiopulmonary Bypass

Objectives:This research is to investigate whether ischemic postconditioning attenuates lung ischemic/reperfusion injury induced by cardiopulmonary bypass in combined mitral and aortic valve replace-ment, to evaluate the protective effects of different algorithms of ischemic postconditioning, and to analyse its possible mechanisms.Methods:24 patients diagnosed as rheumatic mitral and aortic valve disease with or without tricuspid valve disease were randomized into 3 groups:Group A(n=8), patients undergoing routine valve replacement; Group B(n=8), patients undergoing routine valve replacement and ischemic postconditioning by occlusion of the pulmonary artery of five cycles of 15s ischemia and 15s reperfusion before the pulmonary artery totally restoring perfusion; Group C(n=8), patients undergoing routine valve replacement and ischemic postconditioning by occlusion of the pulmonary artery of five cycles of 30s ischemia and 30s reperfusion before the pulmonary artery totally restoring perfusion. The patients' information including age, weight, body surface area, left ventricle, left ventricular ejection fraction, mean pulmonary artery pressure, cardiothoracic ratio were recorded; The duration of aortic cross-clamping, cardiopulmonary bypass(CPB), mechanical ventilation, lung ischemia and monitoring in Intensive Care Unit were also recorded; Oxygenation Indexs were measured at preoperation and 1h,2h,3h,6h and 12h after terminating CPB; The plasma contents of Malondialdehyde(MDA) and Tumor Necrosis Factor(TNF-α) were detected by Enzyme-linked Immunosor- bent Assay at preoperation,1h,3h,6h and 12h after terminating CPB.Results:1. There were no significant differences in Oxygenation Indexs at preoperation and 12h after terminating CPB among 3 groups (ρ>0.05). Compared with group A and C, Oxygenation Indexs in group B significantly increased at 1h,2h,3h,6h after terminating CPB. While there is no significant difference in Oxygenation Indexs between group A and group C at 1h,2h,3h,6h after terminating CPB (allρ>0.05).2. There were no significant difference in plasma contents of MDA and TNF-αbefore surgery among these 3 groups. Compared with group A and C, group B showed significantly reduced MDA and TNF-a contents at 1h,3h,6h,12h after terminating CPB(all P<0.05). While compared with group A, group C showed no significant difference in MDA and TNF-a contents at 1h,3h,6h after terminating CPB(allρ>0.05).3. There were no significantly difference among the duration of aortic cross-clamping, CPB, mechanical ventilation,lung ischemia and monitoring in Intensive Care Unit among these 3 groups (allρ>0.05).Conclusions:In all groups, lung oxygenation function were significantly lower after terminating CPB than that before surgery (ρ< 0.05).2. Ischemic postconditioning by occlusion of the pulmonary artery of five cycles of 15s ischemia and 15s reperfusion attenuates lung oxygenation function injury induced by CPB in combined mitral and aortic valve replacement, and is possibly mediated by inhibiting TNF-αexpression and reducing MDA produced by lipid peroxidation caused by lung ischemic reperfusion injury. However, ischemic postconditioning by occlusion of the pulmonary artery of five cycles of 30s ischemia and 30s reperfusion may not render significant protective effect for lung oxygenation function injury induced by CPB in combined mitral and aortic valve repalcement.