| Lung I/R injury is one of the main complications in heart surgery with Extracorporeal circulation (ECC). As lungs are the only organs which have systemic and pulmonary circulation , so at first lungs had been thought as the anti-ischemia organ generally,but in recent years, with the rapid development of CPB, lung transplant, lungs sleeve shape cutting technology,a large number of animal experimentals and clinical studies showed that lungs are the one of the most vulnerable organs.Lung exist I/R injury, too. Lungs'I/R injury proved to be the main reason caused respiratory function obstacle in early postoperation.During CPB, the only organ that cannot cooling effectively and in high temperature are lungs,a lot of cell factors and leucocyte gathered in lungs.Lung I/R injury has close relationship with inflammation system and I/R injury.Propofol is the most common intravenous anesthetics used in the human body,it had already proved to have favourable antioxidant and could inhibit the release of cell factor.The use of propofol during CPB can reduce lung I/R injury significantly,improve lung's respiratory function and circulatory function, however the studies of exact mechanism of propofol's lung protection and dose correlation is still nothing much.We cannot balance the relationship between propofol's best lung protection and it's best clinical effect in clinical work.Purposes:1 By measuring and calculating clinical value of respiratory index(RI), pulmonary compliance (Cs) and dynamic lung compliance (Cd) who had the heart valve replacement surgery and given different doses of propofol, observe the changes of these indicators before and after CPB to understand the differences of lung protection which had given different doses of propofol.2 By measuring the changes of patients'Superoxide Dismutase (SOD),malondialdehyde(MDA) who had the heart valve replacement surgery and given different doses of propofol, to detect the changes of patients'oxygen free radical(OFR) who had been given different doses of propofol.3 By measuring the changes of patients'Neutrophil Elastase(NE) who had the heart valve replacement surgery and given different doses of propofol, to observe the differences of lung protection who had been given different doses of propofol.Discussion on these issues attempt to clarify lung I / R injury and observe the differences of lung protection who had been given different doses of propofol, to provided for reference could have the best of lung Protection and the best effect of anesthesia.Methods: forty-eight patients who were above to have the heart valve replacement surgery and never had this kind of surgery before are selected randomly. We divided these patients into Group A (propofol dose of 2mg/(kg?h)), Group B (propofol dose of 5mg/(kg?h)), Group C(propofol dose of 8mg/(kg?h)) and the control group Group P (Propofol dose 0mg/(kg?h)) randomly, that P, A, B, C group were given the dose of propofol 0mg/(kg?h), 2mg/(kg?h), 5mg/(kg?h), 8mg/(kg?h) respectively with the use of micro-infusion pump after induction of anesthesia,12 patients each group.Propofol's infusion times are from the central venous puncture complete untill the blood samples were all taken. Blood samples taken time were before CPB(T0), after re-opening the ascending aorta after blocking the ascending aorta 10min(T1),30min(T2),60min(T3), at the same time points radial artery blood (instead of pulmonary vein) samples were taken for determination of SOD,MDA,NE,measuring and calculating Cs,Cd,FiO2, Pb,PaO2,PaCO2,RI.Results:1 There were no significant in patient's age, body weight and the time of operation ,CPB and pulmonary oligemia among 4 groups(P>0.05)2 RI, Cs and Cd comparison, CPB effect Group P the most,followed by Group A,effect Group B,C and the differences were no significanta.There were significant difference between Group B,C and Group P,and the former two groups had better lung protection. Group A had better lung protection than Group P,too.3 The obvious ordinal incremental relations of SOD were presented in Group P,A,B and C,and the difference was significant(P <0.05).Compared with T2,T3 in Group A and T1,T3 in Group B,NE were lower than that in the same time in Group P.Conclusions:1 The use of propofol in heart valve replacement surgery with CPB can improve patients'RI, Cs, Cd significantly, reduce the damage of respiratory function and circulatory function caused by CPB,so it can protect the lungs.Even if the use of propofol is lower than normal dose,the protection is still there, and the protective effect was dose dependent, with the increasing doses the lung protective was increasing.2 Propofol can lighten the degree of lipid peroxidation, prevent the lung I/R injury from the attack of oxygen-derived free radicals;protect the activity of SOD and increased the ability of eliminating the free radicals, so protect the lungs;it also could diminish the intrapulmonary PMN trapping, so it has significantly anti-inflammatory and could protective effect on the lungs against ischemia-radical effects reperfusion injury induced by CPB. We found that even the use of propofol is lower than normal dose,the protection is still there, and the protective effect was dose dependent, with the increasing doses the lung protective was increasing. However,the differences between Group B and Group C are not that clear suggest that the protection isn't even more when to a certain depth of anesthesia.3 Although propofol can not prevent the I/R injury caused by CPB completely, it can lessen the lung I/R injury. In this study, three patients (all continuous infusion of propofol 8mg/(kg?h)) intraoperative hypotension is difficult to maintain, given vasoactive drugs didn't work and when we stop pumping propofol the blood pressure return,it shows inhibitory effect of propofol on the myocardium is still very strong, and these three blood samples were all abandoned.Therefore increasing the dosage of propofol blindly are not recommended in clinical work.We recommend that the premise of protecting patient safety, you can increase the appropriate dose of propofol to have better lung protection.
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