MICROVASCULAR APPROACH TO CEREBRAL DISORDERS IN CARDIOPULMONARY BAYPASS

本研究观察了常温下体外循环（CPB）大鼠脑微循环的变化，以探讨CPB手术引起的脑血管疾病。通过改变血流速度使动脉压从50 mmHg变化到200 mmHg，用纤颤仪阻断心脏搏动建立无搏动血流模型，用荧光显微镜观察软脑膜微循环，并与正常对照组比较。在体外循环（CPB）心脏不停跳和心脏停跳时，静脉注射标记红细胞和葡聚糖，在荧光显微镜下直接观察动脉内径和红细胞流速，根据记录的血流速度，在动脉中选择直径约为40 μm的单支动脉，测量动脉内径和红细胞流速。动脉血管扩张（或血管收缩）在脉动流期间出现，但在非脉动流期间消失，动脉红细胞活力增加在非脉动流和脉动流期间，在脉动流期间，在60 - 160 mmHg的平均动脉压的大范围内，流速几乎恒定，但在非脉动流期间，流速随着平均动脉压的增加或减少而增加或减少，这表明脉动可能是大脑自动调节的原因。

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.