Microcirculatory hemodynamic changes in cererbral microvascular occusion

通过对猫和大鼠脑脊液微循环的活体显微观察，研究了脑微血管闭塞时脑微循环血流动力学的变化。采用戊巴比妥钠麻醉，机械通气。开颅后，准备一个封闭的颅窗。我们用荧光视频显微镜系统对脑皮层表面的微循环进行了直接观察。fitc标记的红细胞和RITC（罗丹明- b）标记的葡聚糖分别用于观察微血管和血流。将经FITC标记的乳胶微片（直径约40 μ m）注入颈总动脉，作为微栓子模型。在RITC视频图像的基础上，测量了颅底微血管的内径、长度和网络结构。基于FITC视频图像，我们使用双窗口技术测量红细胞速度。通过扫描大脑皮层表面的一个区域，我们重建了微血管的网络结构。荧光影像显示：(1)脑皮质微血管（小动脉和小静脉）呈有序结构，小动脉-小动脉吻合；Ii)小动脉拱廊为血液流动提供了多种途径。由于小动脉拱廊就像一个连接主干的旋转，当单个小动脉被微球堵塞时，血液流动不会停止。在微栓子引起的微血管闭塞情况下，旁路血流回路可以在大脑微血管网络中工作，使血液持续流动。

Cerebral microcirculatory hemodynamic changes were investigated during cerebral microvascular occlusion, based on an intravital microscopic observation of the pial microcirculation in cat and rats. The animals were anesthetized with pentobarbital sodium and mechanical ventilated. After craniotomy, a closed cranial window was prepared. We made a direct observation of the microcirculation on the cerebrocortical surface using a fluorescence videomicroscopic system. FITC-labeled red cells and RITC (Rhodamine-B) labeled dextran were used for visualzing microvessels and blood flow, respectively. As a model of microemboli, latex microsheres (diameter : around 40 mum), which were labeled with FITC,were injected into a common carotid artery. Based on RITC video-image, we measured internal diameter, length and network structure, of pial microvessels. Based on FITC videoimage, we measured red cell velocity, using a dual window technique. By scanning over an area of the cerebrocortical surface, we reconstructed the network structure of microvessels. The present fkuorescence videoimage showed that i) cerebrocortical microvessels (arterioles and venules) show an acrcading structure with arteriole-arteriole anastomoses ; ii) the arteriolar arcade proivides a multiple pathway for blood flow. Since the arteriolar arcade was like a rotary to connect main streams, blood flow was never stopped when a single arteriole was occluded with microspheres. Under microvascular occlusion due to microemboli, dypath flow-circuits may work to flow blood continuously in the cerebral microvascular network.