改良小儿主动脉阻闭钳对血管壁损伤的电镜观察

Electron microscopic observation of vascular wall injury caused by a modified pediatric aortic blocking forceps incarceration

目的探索改良小儿主动脉阻闭钳夹闭不同时限对血管壁的损伤程度。方法将50只犬随机分为A、B、C、D、E5个组,每组10只,E组为对照组(不夹闭主动脉)。经股动静脉插管建立体外循环,胸腔镜下阻闭升主动脉,经主动脉根部冷灌使心脏停跳。A、B、C、D4组分别阻闭0.5h、1h、2h、3h开放循环,再灌流至24h后处死动物。取夹闭段主动脉,在电子显微镜下观察血管壁超微结构的改变。结果与E组相比较,A组未见明显损伤。B组内膜表面粗糙,内皮细胞和平滑肌细胞中的线粒体轻度肿胀,其间可见少量胶原蛋白和弹性蛋白。C组可见内皮细胞缺失,线粒体肿胀,中膜层增厚,平滑肌伸出突起达内皮下层,部分可见内皮细胞层与内弹力膜层分离。D组内皮细胞缺失明显,细胞核出现固缩,线粒体呈空泡样变,弹性纤维有断裂,部分或完全内皮细胞层脱落。结论血管对夹闭的最大耐受时间为2h,若延长夹闭的时间,可引起血管壁不可逆的损伤。

AIM To explore the vascular injury caused by a modified pediatric aortic blocking METHODS Fifty dogs were randomly divided into A, B, C, D and E groups of 10 dogs each. was the control group. Intraoperatively, cardiopulmonary bypass （CPB） was established through forceps. E group femoro-femoral cannulation with Bi-caval femoral venous cannula and one stage femoral arterial cannula. Under the guidance of thoracoscope, ascending aorta was clamped through thoracic port with modified pediatric aortic blocking forceps. High-potassium cold blood cardioplegia was administered through direct ascending aortic needle and the heart was arrested. In A, B, C, D groups, the ascending aorta was temporarily blocked for 0.5 h, 1 h, 2 h and 3 h respectively, followed by a 24-hour reperfusion before execution. The clamped aortic vessel was collected, observed and photoed through scanning electron microscope （SEM） and transmission electron microscope （TEM）. RESULTS TEM and SEM showed no ultramicro-structure injury in group A. Vascular endothelial surface was rough in group B and the cytoplasm contained slightly swollen mitochondria in the endothelial cells and the smooth muscular cells, among which newly-formed collagen and elastin were taking shape. In group C, SEM showed that vascular endothelial cells decreased. Swollen mitochondria in the cytoplasm were observed through TEM. Vascular tunica media with elastic fiber thickened and smooth muscular cells had protruding part which penetrated the internal elastic lamina and reached endotheliocytes. The endothelium was separated from the internal elastic lamina in some cases. In group D, more vascular endothelial cells lost. Karyon of endothelium appeared contracted and mitochondria were vacuole denaturalization. Elastic fibers were ruptured and part of endothelium had peeled off. CONCLUSION The maximum time span of clipping the vessel-wall can endure is 2 hours. Prolonged clipping time can cause local vascular cavity stenosis and thrombosis, thus leading to vascular irreversible injury.