肺缺血预处理对深低温停循环肺损伤保护的实验研究

The experimental research of lung protection mechanism in deep hypothermic circulatory arrest cardiopulmonary bypass

摘要:

目的：评估肺缺血预处理（Ischemic preconditioning，IP）对心脏手术深低温停循环（Deep hypothermic circulatory arrest，DHCA）中肺损伤的保护效果。方法：24只幼猪随机分4组：常规体外循环（Cardiopulmonary bypass，CPB）再灌注组（基线组，n=6）、无肺IP的DHCA组（对照组，n=6）、单纯肺IP的DHCA组（IP-1组，n=6）和合并肺缺血缺氧预处理的DHCA组（IP-2组，n=6）。在CPB前、结束即刻和结束后1 h分别检测左心房（Left atrium，LA）和肺动脉（Pulmonary artery，PA）血中TNF-α、IL-8、IL-10水平以及中性粒细胞、单核细胞上CD18的表达值，计算LA/PA值衡量肺区释放炎症介质量和激活白细胞量；取小块肺组织测肺湿干重比。结果：（1）4组CPB后TNF-α、IL-8和IL-10的LA/PA值均增加；相对基线组，TNF-α对照组和IP-1组CPB后1 h显著增加，IL-8对照组CPB后两时点和IP-1组CPB结束即刻显著增加，IL-10都显著升高；相对对照组，TNF-α仅IP-2组CPB后1 h显著降低，IL-8、IL-10两IP组都显著降低；（2）CPB后单核细胞上CD18表达值比值仅对照组显著降低，而中性粒细胞上CD18表达值比值，IP-1组CPB后1 h和对照组、IP-2组CPB后两时点均显著降低；相对基线组单核细胞上比值仅对照组CPB后两时点和IP-1组CPB后1 h显著降低，中性粒细胞上比值，对照组、IP-1组显著降低，IP-2组仅CPB结束即刻显著降低；相对对照组单核细胞上比值IP-2组CPB后1 h显著增加，中性粒细胞上比值，IP-1组和IP-2组也均在CPB后1 h显著增加；（3）肺湿干重比值，对照组、IP-2组在CPB后显著增加，IP-1组仅在CPB后1 h显著增加；与基线组比较，对照组CPB后两时点和IP-1组CPB后1 h显著增加；与对照组比较，仅IP-2组比值显著减少。结论：研究示DHCA加剧了体外循环肺组织炎症反应，证实了肺IP可以减轻DHCA缺血再灌注炎症反应性肺损伤；合并肺缺血缺氧预处理的DHCA组相对于单纯肺IP的DHCA组，对肺功能具有更好的保护趋势。

Abstract:

Objective：To investigate whether lung IP for a short period prior to surgery is sufficient to prevent symptoms of lung ischemia reperfusion injury（LIRI），especially the inflammatory response. Methods：24 piglets were divided randomly into four groups：regular CPB reperfusion group（baseline group，n=6），DHCA group without lung IP（control group，n=6），DHCA group with single pulmonary artery（PA） perfusion twice in the lung IP process（IP-1，n=6），and DHCA group with lung ventilation together with PA perfusion twice in the lung IP process（IP-2，n=6）. Blood was simultaneously drawn from the left atrium（LA） and thepulmonary artery（PA）；The levels of TNF-α，IL-8 and IL-10，as well as the adhesion molecules CD18 on leukocytes，were determined. As a measure of the pulmonary release，ratios of LA/PA levels were calculated.A piece of lung tissue was taken to measure the wet to dry lung weight ratio（W/D） at three time points. Results：（1）The lung itself significantly produced more TNF-α，IL-8 and IL-10 after CPB in each group；Compared with baseline group，LA/PA ratios for TNF-α at 1 h post-CPB in both control group and IP-1 group were signifi－cantly increased，the ratios for IL-8 in control group after CPB and in IP-1 group at the end of CPB were significantly increased，the ratios for IL-10 in other three groups were all increased；Compared with control group，LA/PA ratios for TNF-α in IP-2 group at 1 h Post-CPB were significantly decreased，the ratios for IL-8 and IL-10 were all significantly decreased in IP groups.（3）Compared with Pre-CPB，LA/PA ratios of CD18 on monocytes only in control group significantly decreased after CPB，whereas ratios of CD18 on PolymorPhonuclear leukocytes（PMNs）in IP-1 group at 1 h Post-CPB and in both control group and IP-2 group after CPB were significantly decreased；Compared with baseline group，LA/PA ratios of CD18 on monocytes in control group after CPB and in IP-1 group at 1 h Post-CPB were significantly increased，the ratios of CD18 on PMNs in both control group and IP-1 group after CPB and in IP-2 group at the end of CPB were significantly increased；Compared with control group，LA/PA ratios of CD18 on monocytes in IP-2 group and ratios of CD18 on PMNs in both IP-1 and IP-2 groups at 1 h Post-CPB were significantly increase.（4）Compared with Pre-CPB，lung W/D ratios in both control and IP-2 group after CPB and in IP-1 group at 1 h Post-CPB were significantly increased；Compared with baseline group，ratios in control group after CPB and in IP-1 group at 1 h Post-CPB were significantly increased；Compared with control group，only in IP-2 group the ratios signifi－cantly decreased. Conclusion：Our data indicate that DHCA aggravates lung inflammatory response during CPB；lung IP has a pro－tective effect in LIRI during DHCA；moreover，maintaining ventilation together with PA perfusion in the lung IP process during CPB trends to excel single PA perfusion.