Experimental Study About Lung Protection During Cardiopulmonary Bypass

Aim: One of the aims of this study was to establish convenient and reasonable animal models of CPB-induced lung injury, observe the influence of pulmonary perfusion on the lung, and further research effective perfusion modus and perfusion pressure. The other aim of this study was to observe the effect on lung while applying lipo-PGE1 on the basis of pulmonary perfusion, and to expect to expand the way of lung protection in cardiosurgery.Methods: The experiment consisted of two parts. In the first part, twenty healthy canis familiaris were randomly divided into four groups, including a control group and three perfusion groups (low-pressure group, moderate-pressure group, high-pressure group). Simulate the characteristics of clinical CPB and establish animal models of lung injury. During CPB, pulmonary perfusions were performed respectively in the three perfusion groups with different pressures, while the control group was free of perfusion. After 90 minutes of CPB and hours of reperfusion, change of pulmonary functions and tissue damage items were determined in the experimental lung. Change of pulmonary functions was expressed as the ratio of change between baseline pulmonary function value and post-reperfusion pulmonary function value, I.e.: | baseline pulmonary function value-post-reperfusion pulmonary function value |÷baseline pulmonary function value.The second part was designed basing on the results of the first part. Ten healthy canis familiaris were randomly divided into two groups: one was pulmonary perfusion group, and the other was pulmonary perfusion + lipo-PGE1 group, which was definite as the associated application of lipo-PGE1 on the basis of pulmonary perfusion. Simulating the characteristics of clinical CPB and considering pharmacological properties of the intervention medicine, we established animal models of lung injury. After 90 minutes of CPB and hours of reperfusion , changes of pulmonary functions and tissue damage items were determined in the experimental lung.Results: In the first part of this experiment, in all groups there had different degrees of aggravation in lung compliance, oxygenation and PVR after reperfusion, but compared with that in the control group, the rangeabilities of three above-mentioned items were all decreased in the moderate-pressure group(lung compliance: 31% versus 19%,p < 0.01;oxygenation: 58% versus 34%,p < 0.01; PVR: 97% versus 51%,p < 0.01); malonaldehyde's concentration in pulmonary venous blood, neutrophile's sequestration, ICAM-1 gene's transcription and ICAM-1's production in lung also decreased significantly in the moderate-pressue group(respectively 32.4 nmol/ml versus 20.5 nmol/ml,p < 0.01; 0.27 versus 0.14,p < 0.01; 0.569 versus 0.341,p < 0.01; 36.45 ng/ml versus 22.82 ng/ml,p < 0.01). In the low-pressure group, the all above-mentioned pulmonary function and tissue damage items were further improved. There were not significant difference of the all items between the control group and the high-pressure group. The examination of histopathology demonstrated that the tissue changes (such as inflammatory cell infiltration, intra-alveolar hemorrhage and exudation, local alveolar wall engorgement and destruction) in the control group and high-pressure group were more obvious than that in the moderate-pressure group , and these changes in the low-pressure group appeared slighter than that in the moderate-pressure group.In the second part of this experiment, compared with the perfusion group, the associated application of lipo-PGE1 during CPB could further inhibit the aggravation of lung oxygenation, and reduce malonaldehyde's concentration, neutrophile's sequestration , ICAM-1 gene's transcription and ICAM-1's production . Although there were not significant differences between the two groups in the rangeabilities of lung compliance and PVR, but there was decrease tendency in the later group. The changes of histopathology appeared a little improvement in the later group too.Conclusions: The pulmonary perfusion used in this experiment could relieve the lung injury correlative with ECC; perfusion pressure was an important factor influencing protection effect, and compared with higher pressure, the pressure of 15-20mmHg conduced to more predominant protection; during CPB, associated application of lipo-PGE1 on ground of pulmonary perfusion could further relieve lung injury and protect oxygenation.