深低温停循环对大鼠脑组织形态学的影响

Effects of deep hypothermia circulation arrest on morphologic changes of rat brain

目的建立接近临床环境的大鼠深低温停循环(DHCA)模型,并进一步研究DHCA对大鼠脑组织形态学的影响。方法雄性SD大鼠随机分为实验组和假手术对照组。以氯胺酮、芬太尼和氟哌利多混合液麻醉动物,经口明视下行气管插管。实验组动物实施体外循环,预充液总量为20ml(乳酸林格液10ml、20%甘露醇1ml、肝素1ml即100U、6%贺斯8ml)。降温至18℃停循环90min,术中监测血气分析、血压和心率变化。复温、复灌60min后处死动物。灌注后取脑分别进行病理学检查和电镜观察。结果实验组有3只大鼠因为颈静脉插管失败死亡,其余动物顺利完成实验。无血预充后的红细胞压积(HCT)约为0.20。病理检查结果发现在大鼠的海马区、皮层和丘脑都存在数量不等的变性坏死神经元,电镜下表现为线粒体肿胀和胞浆内细胞器减少甚至消失。结论本实验建立的大鼠DHCA模型预充量小,与临床情况更为接近,并且制作简单,需要的人力、物力较少,便于广泛开展。形态学研究结果进一步证实该模型是成功的,同时为深入研究DHCA术后的神经并发症提供了形态学基础。

Objective To develop a new rat model of deep hypothermia circulation arrest （DHCA） that functionally mimic the clinical setting and to study the effects of DHCA on the morphologic changes of the rat brain. Methods Male Sprague-Dawley rats were randomly divided into two groups, experimental group and the sham-operation group. Anesthesia was induced using a mixture of fentanyl, ketamine and droperidol, then the rat was intubated through the mouth under direct vision. The rats of the experimental group underwent extracorporeal circulation circuit priming without blood which consisted of 10 ml of Ringer lactate solution, 20% mannite 1 ml, heparin 1 ml （100 U） and 6% HES 8 ml. The body temperature of the rats was reduced to 18℃ and then paused the extracorporeal circulation circuit for 90 min. Blood gas analysis, blood pressure and heart rate monitorings were performed during the experiment. After 60 min of rewarming and resuming the extracorporeal circulation circuit, the rats were sacrifical perfused and the brains were dissected for examination by light microscopy and electronmicroscopy. Results Three rats of the experimental group died because of failure of jugular vein cannulation, the rest passed the experiment thoroughly and uneventfully. The hematocrit was about 20% after the extracorporeal circulation circuit. Degeneration and necrosis of the neurons could be found at the hippocampus, cortex and the thalamus after DHCA. With electronmicroscopy, swelling of mitochondria was found and organelles in the cytoplasm reduced or even disappeared. Conclusions The entire circuit is similar to clinical setting in terms of its construction, configuration, performance and priming volume to blood volume ratio. The new rat model of DHCA is easy to create and the morphologic changes have been proved to be a successful rat model for future study of neurological injury under DHCA. （Shanghai Med J, 2005,28..862-865）