MICROVASCULAR APPROACH TO CEREBRAL DISORDERS IN CARDIOPULMONARY BAYPASS

本研究通过对常温下心肺停跳（cpb）大鼠脑微循环变化的研究，探讨cpb手术所致脑血管疾病。在大鼠CPB系统中，通过改变泵流量，动脉压从50 mmHg改变到200 mmHg。利用颤振器停止心脏搏动，建立了非脉动流模型。采用荧光标记红细胞和静脉注射葡聚糖观察脑脊液微循环，并在有/无心脏跳动的CPB过程中直接在荧光视频显微镜下观察。根据所记录的视频图像，选取直径约为40μm的小动脉，评价动脉直径和红细胞流速。结果表明：1)当动脉压发生变化时，脉动血流时出现小动脉血管扩张（或收缩），非脉动血流时血管收缩消失；2)非脉动血流和脉动血流时小动脉红细胞流速均呈线性增加（降低）。脉动血流时，平均动脉压在60 ~ 160 mmHg范围内，血流速率基本不变，而非脉动血流时，血流速率随平均动脉压的升高或降低而升高或降低。有人认为，搏动性可能与大脑的自动调节有关。

THIS STUDY INVESTIGATED CEREBRAL MICROCIRCULATORY CHANGES IN RAT WITH A CARDIOPULMONARY BAYPASS (CPB) AT NORMOTHERMIA TO ELUCIDATE CEREBROVASCULAR DISORDERS CAUSED BY SURGICAL OPERATION WITH CPB.IN THE RAT CPB SYSTEM, THE ARTERIAL PRESSURE WAS CHANGED FROM 50 TO 200 mmHg BY CHANGING THE PUMP FLOW-RATE.A NON-PULSATILE FLOW MODEL WAS DEVELOPED BY STOPPING CARDIAC BEAT USING A FIBRILATOR.THE PIAL MICROCIRCULATION WAS VISUALIZED USING FLUORESCENCE-LABELED RED CELLS AND DEXTRAN INJECTED INTRAVENOUSLY, AND WAS DIRECTLY OBSERVED UNDER A FLUORESCENCE VIDEOMICROSCOPY DURING CPB WITH/WITHOUT CARDIAC BEATING.BASED ON THE RECORDED VIDEOIMAGES, THE ARTERIOLAR DIAMETER AND RED CELL VELOCITY WERE EVALUATED WHERE SINGLE ARTERIOLES WITH APPROX.40μm DIAMETER WERE SELECTED AMONG THE PIAL ARTERIOLES.THE PRESENT RESULTS SHOWED THAT 1) WHEN THE ARTERIAL PRESSURE CHANGED, ARTERIOLAR VASODILATION (OR VASOCONSTRICTION) APPEARED DURING PULSATILE FLOW BUT IT DISAPPEARED DURING NON-PULSATILE FLOW, AND 2) THE ARFTERIOLAR RED CELL VELOCITY INCREASED (DECREASED) LINEARLY DURING NON-PULSATILE FLOW AS WELL AS PULSATILE FLOW.THE FLOW-RATE WAS ALMOST CONSTANT AT A LARGE RANGE OF THE MEAN ARTERIAL PRESSURE FROM 60 TO 160 mmHg DURING PULSATILE FLOW, BUT THE FLOW-RATE INCREASED OR DECREASED DURING NON-PULSATILE FLOW WITH AN INCREASE OR DECREASE IN MEAN ARTERIAL PRESSURE, RESPECTIVELY.IT WAS SUGGESTED THAT PULSATIVITY MIGHT BE RESPONSIBLE FOR CEREBRAL AUTOREGULATION.