地塞米松对体外循环下心脏瓣膜置换术患者肺弥散功能的保护作用

Effect of dexamethasone on pulmonary diffusion in patients undergoing cardiac valve replacement under cardiopulmonary bypass

目的评价地塞米松对体外循环(CPB)下心脏瓣膜置换术患者肺弥散功能的保护作用。方法择期CPB下行心脏瓣膜置换术患者40例,年龄29～47岁,体重50～69kg,ASAⅡ或Ⅲ级,随机分为2组(n=20)：对照组和地塞米松组。地塞米松组于麻醉诱导后即刻静脉注射地塞米松0.5 mg/kg,对照组给予等量生理盐水。在手术前即刻、转流前即刻和停机时经中心静脉采血,分离乏血小板血浆,提取总RNA,分别测定血浆总基质金属蛋白酶-9浓度、活性基质金属蛋白酶-9浓度及基质金属蛋白酶-9mRNA表达,并在转流前即刻和停机时进行动脉血血气分析,计算肺泡-动脉氧分压差。结果与手术前即刻比较,停机时两组基质金属蛋白酶-9mRNA表达、血浆总基质金属蛋白酶-9、活性基质金属蛋白酶-9浓度和基质金属蛋白酶-9激活程度均升高,但地塞米松组低于对照组(P＜0.05或0.01)；与转流前即刻比较,停机时两组肺泡-动脉氧分压差升高,但地塞米松组低于对照组(P＜0.05)。结论地塞米松对CPB下心脏瓣膜置换术患者肺弥散功能有一定的保护作用,与抑制基质金属蛋白酶-9的表达和活性有关。

Objective To investigate the effect of dexamethasone on the pulmonary gas exchange in patients undergoing cardiac valve replacemem under cardiopulmonary bypass （ CPB）. Methods Forty ASA 11 or m patients aged 29-47 yrs weighing 50-69 kg undergoing cardiac valve replacement under CPB were randomly divided into 2 groups （ n = 20 each） ： dexamethasone group received dexamethasone 0.5 mg· kg^-1 after induction of anesthesia and control group received normal saline （NS）. Blood samples were taken before operation （T0） immediately before CPB （T1） and immediately after discontinuation of CPB （T2 ） for determination of plasma total and active matrix metallo-proteinase-9 （MMP-9） concentration （by enzyme-linked immuno-absorbent and fluorometric enzyme-linked immuno-absorbent assay respectively） and MMP-9 gene expression （RT-PCR）. Blood samples were taken from radial artery at Tl and T2 for blood gas analysis. A-aDO2 was calculated. Results MMP-9 gene expression and plasma total and active MMP-9 concentrations were significantly increased at T2 as compared with those at To in both groups and were significantly lower in dexamethasone group than in control group （ P 〈 0.05 or 0.01 ） . The A-aDO2 at T2 was significantly smaller in dexamethasone group than in control group. Conclusion Dexamethasone can inhibit the increase in gene expression, protein synthesis and activation of MMP-9 and decrease in gas exchange across alveolar-capillary membrane caused by CPB and protect the lungs during open heart surgery performed under CPB.