Experimental Study On Cardiopulmonary Bypass In Canine Lung Protective Effect And Mechanism Of Sevoflurane Postconditioning

Objective: To investigate the protective effect of lung and expression of Bcl-2and Bax indogs by sevoflurane postconditioning in cardiopulmonary bypass (CPB) and itsmechanism.Methods: Twelve experiment hybrid dogs were randomly divided into two groups(either male or female): Ischemia-reperfusion group with left lung (group C, n=6),sevoflurane preconditioning group (group Y, n=6). Two groups were intraperitonealinjected sodium pentobarbital (25mg·kg-1), then operated endotracheal intubation.Afemoral artery catheter was placed for mean arterial pressure (MAP) monitoring. Afemoral vein catheter was placed for central venous pressure (CVP) monitoring. Group Cwas used to establish ischemia-reperfusion injury model of the left lung, and dogs in thegroup Y received ischemic postconditioning with sevoflurane after opening the pulmonaryartery. Samples of lung tissue were collected at T1(in front of the CPB), T2(opening thepulmonary artery), T3(2hours after CPB) for observed the changes of pathology with lightmicroscope and measured the level of Bcl-2and Bax by immunohistochemistry. Samplesof arterial blood were used to calculate respiration index (RI), oxygennation index (OI) anddynamic lung compliance (Cd).Results:(1) Pathology change and the score of lung tissue under optical microscope: Thestructure of lung tissue was clear, the alveolar septum was not obviously expanded andthere was no significantly alveolar cavity exudate between two groups before CPB,but thestructure of lung shown as disorder, much of inflammatory cell infiltration and very fewalveolar walls fracture after opening the pulmonary artery.The lung tissue damage of groupC and group Y at two hours after CPB was much more serious than before.The scores of lung tissue: There was no significant difference in the scores of lungtissue between two groups before CPB (P>0.05). Compared with T1time point, the scoresof lung tissue at T2time point were markedly increased in two group（sP <0.05）.The scoresof T3time point were higer than that of T2time point in two groups（P <0.05）.There wasno obvious difference in the the scores of lung tissue between two groups at T1and T2 time point（P>0.05）. The scores of group C was higer than that of group Y at T3timepoint (P<0.05).(2) The change of index of respiratory function: Compared with T1time point, the RI oftwo groups gradually increased with time, the Cd and OI were on the contrary (P <0.05).There was no significant difference in Cd, OI and RI between two groups at T1, T2timepoint (P>0.05), the Cd and OI of group Y at T3time point significantly higher than that ofgroup C（P <0.05）,but the RI was on the contrary（P <0.05）.(3) The change of expression of Bcl-2and Bax in the lung tissue of dogs: Comparedwith T1time point, the expression of Bcl-2and Bax in all groups was significantlyincreased at T2and T3time point (P <0.05). There was no significant difference in theexpression of Bcl-2and Bax between group C and group Y at T1and T2time point(P>0.05). The expression of Bax of group C was significantly higher than that of Y groupat T3time point (P <0.05), but the expression of Bcl-2was on the contrary (P <0.05).There was no significant difference in the ratio of Bcl-2/Bax between two groups at T1andT2time point (P>0.05), and the rario of Bcl-2/Bax of group C was higer than that of groupY at T3time point (P <0.05).Conclusion: Sevoflurane postconditioning has a certain protective effect with lung afterCPB in dogs and the mechanism maybe associate with promoting the expression of Bcl-2and suppression the expression of Bax.