低温对缺血预调心肌保护作用的影响

The Effect of Ischemic Preconditioning on Myocardial Protection

目的：为确定体外循环心脏直视手术时应用“缺血预调”（ＩＰＣ）的可能性，分别在两部分实验中研究了（１）ＩＰＣ对长时间低温缺血心肌的保护作用。（２）ＩＰＣ期间心肌低温对ＩＰＣ诱导心肌保护作用的影响。方法：建立离体灌注的大鼠工作心脏模型，稳定后施行不同的预调方案，进而缺血停搏。在预调处理前和缺血再灌注后两次测定工作心脏的主动脉流量（ＡＦ）。在第一部分研究中，离体心脏在１８℃低温条件下缺血６０分钟，ＩＰＣ方案为１ｂ组：５分钟缺血＋５分钟再灌注（５×１）；１ｃ组：５分钟缺血＋５分钟再灌注，反复２次（５×２）；１ｄ组：５分钟缺血＋５分钟再灌注，反复３次（５×３）。１ａ组为对照组，缺血前不施行预调处理。在第二部分研究中，离体心脏在３７℃条件下常温缺血１５分钟，实验组（包括６组：ＩＩ，ＩＩ，ＩＶ，Ｖ，ＶＩ和ＶＩ组）的预调方案均为５×１，但ＩＰＣ期的心肌温度不同，其中：ＩＩ组为３７℃，ＩＩ组３２℃，ＩＶ组２７℃，Ｖ组２２℃，ＶＩ组１７℃，ＶＩ组１２℃。Ｉ组为对照组，缺血前不施行预调处理。结果：在第一系列研究中，对照组的主动脉流量（ＡＦ）仅恢复到缺血前的２．７％。预调各组的ＡＦ恢复程度显著提高，与对照组比较１ｂ组为２２％（Ｐ＜?

Aim:To evaluate the effect of ischemic preconditioning(IPC)on myocardial protection and the effect of temperature on IPC.Material and method:This study consisted of two parts of work.Isolated rat working heart models were used in both studies.Study I was divided into four subgroups.Group Ia(control) received 60 minutes ischemia under normothermia(37℃)without IPC.In group Ib,IPC was carried out before 60 minutes ischemia with 5 minutes ischmia and followed by 5 minutes reperfusion.In group Ic and Id,IPC was repeated 2 times and 3 times,respectively.There were seven subgroups in study II.Group IIa received 20 minutes ischemia under normothermia(37℃) IPC。IPC was performed before 20 minutes ischemia under the different temperaure in group IIb to IIg(32℃,27℃,22℃,17℃,and 12℃ for each group,respectively).Aortic flow was measured before ischemia arrest and after reperfusion.Results:In study I,aortic flow significantly improved for group Ib Id(recovered to 22%,34%and 15% of preischemic value,respectively)when compared with group Ia(2.7%).In group II,aortic flow was significanlty improved in group IIb IIe(76%,70%,71% and 62% of preischemic value,respectively).While in group IIa,IIf and IIg,aortic flow was markedly decreased(only recovered to 17%,17% and 14% of preischemic value,respecteively).Conclusons:The results of this study indicated that IPC is an effective method for myocardial protection under normothermia and hypothermia(>22℃,22℃ might be taken as a borderline.Temperatures below 22℃ made IPC ineffective.)Conclusion:IPC may play an important role on myocardial protection during open heart surgery,under specific conditions.