猴脑选择性深低温断血流复苏对认知功能影响的研究

At present, whole body deep hypothermic circulatory arrest(DHCA) was used clinically. However, there are many complications that limit its broad use, e.g. the interval of blood flow occlusion is usually less than 60 min. Studies have shown that: antegrade cerebral perfusion after total blockage of macaca mulatta's bilateral carotid artery, reduced brain temperature to 18 ℃, the temperature maintained above 33 ℃, the brain is selectively cooled and the brain may extend the time limit for blood safety blockage, the main organs of the body will not be significantly damaged, but the impact on cognition is not clearly understood. However, cerebral selective deep hypothermia combined with antegrade cerebral perfusion can not only avoid these side effects effectively but also extend the limitation of blood flow occlusion by more depressed metabolism in macaca mulatta whicn is not sure if there is cognitive dysfunction.We established the model of macaca mulatta of resuscitation after selective cerebral deep hypothermia and blood flow occlusion in macaca mulatta , on the base of this, We improve the ways of preparing the model of macaca mulatta. In order to explore the mechanism which reduce the cognitive dysfunction and is resistant to hypoxia-ischemia, we do something as follows:1.To study event-related potentials(ERP) and electroencephalogram(EEG) of macaca mulatta of resuscitation after selective cerebral deep hypothermia blood flow occlusion 2. To investigate magnetic resonance imagine(MRI) and magnetic resonance spectroscopy(1H-MRS)related to cognition of macaca mulatta of resuscitation after cerebral selective deep hypothermic and blood flow occlusion, 3.To Use delayed response experiment detects working memorys. All of these we do is to explore the mechanism of selective cerebral deep hypothermia reducing the complications and being resistant to hypoxia-ischemia in different aspects, which let us to use it rationally in clinical in the future.

临床使用的深低温停循环技术，其断血流的安全时限常不能满足临床工作的需要，且易引起心肺并发症和认知功能损害。研究表明：阻断猴双侧颈总动脉后行顺行性脑灌注，降低脑温至18℃，体温保持在33℃以上，使脑选择性降温，可延长脑对血流阻断的安全时限，对全身主要器官无明显损害，但对认知功能的影响缺乏了解。本研究拟在改进脑选择性深低温断血流复苏模型的基础上，采用事件相关电位和脑电对脑选择性深低温断血流复苏前后与认知相关的神经电生理活动进行研究；用MRI动态观察有无缺血梗塞灶；用1H-MRS检测复苏前后与认知相关的前额叶及海马的神经元密度和活性变化；并采用延缓反应来进行猴工作记忆的检测。其结果有助于从认知功能角度认识选择性深低温脑保护技术的有效性和安全性，为临床应用此项技术提供实验基础和理论依据。

脑是依赖有氧代谢的高耗能器官，常温条件下，缺血、缺氧4到5分钟就可引起脑细胞的损伤，超过此时限即可引起不可逆的神经元损害。本研究在制备脑缺血模型的基础上，阻断猴双侧颈总动脉10分钟后行选择性脑灌注，降低脑温至17-27℃，体温保持在33℃以上，使脑选择性降温，提高脑对缺血缺氧的耐受性，探讨常规核磁共振（magnetic resonance imagine, MRI）和磁共振氢质子波谱(1H/protion magnetic resonance spectroscopy,1H-MRS)在猴脑选择性深低温断血流复苏前后的表现，研究脑选择性深低温断血流对猴脑组织形态及细胞生化代谢的影响；通过病理学方法观察认知相关脑区以及心肺等重要器官组织结构和超微结构变化。采用脑电图观察实验猴的神经电生理活动，在术前术后进行猴工作记忆的检测。.我们按计划完成了对实验猴的延缓反应训练，随机分组进行了猴脑选择性深低温断血流复苏模型的制备。深低温灌注组灌注60分钟后安全复苏并长期存活，术后脑电图正常，脑及主要器官组织形态未见异常，脑组织细胞超微结构未见明显异常。常温灌注组灌注60min后以及单纯缺血组均未能安全复苏，全部死亡，主要器官组织形态可见不同程度异常。等温灌注组行脑组织细胞超微结构观察示神经细胞水肿、神经细胞核固缩、神经毯水肿，有髓神经纤维脱髓鞘。细胞器病变主要为线粒体肿胀，嵴溶解；内质网扩张，内质网脱落颗粒等。实验猴分别于手术前及手术复苏后进行了认知行为学测试，在选择性深低温复苏前后进行了MRI检查，没有发现明确缺血梗塞灶；1H-MRS采集、分析认知相关脑区（前额叶，海马）的微量代谢物NAA、Cho、Cr在选择性深低温断血流复苏前后变化均无显著性差异。.猴脑选择性深低温断血流复苏后，动物正常存活，通过术前术后认知行为学测试、磁共振波谱分析以及病理学观察等，我们发现低温对严重缺血后的脑保护作用是确切有效的，可认为恒河猴严重脑缺血后行选择性脑深低温灌注可以明显改善脑缺血的预后。