MICROVASCULAR APPROACH TO CEREBRAL DISORDERS IN CARDIOPULMONARY BAYPASS

为阐明体外循环手术所致脑血管疾病，本研究观察了常温下体外循环(CPB)大鼠脑微循环的变化。在大鼠CPB系统中，通过改变泵的流量，使动脉压在50~200 mm Hg之间变化。用纤颤器停止心脏跳动建立非脉动血流模型。用荧光标记的红细胞和葡聚糖静脉注射显示大脑微循环，并在荧光显微镜下直接观察CPB期间有无心脏停搏的情况。在记录的VIDEOIMAGES上，结果表明：1)当动脉压力变化时，脉动流时微动脉扩张(或收缩)，而非脉动流时则消失；2)非脉动流和非脉动流时，动脉血流速度呈线性增加(降低)。在脉动期，平均动脉压在60~160μ之间，流量几乎不变，但在非脉动流时，流量增大或减小研究表明，PULSATITY可能与脑自身调节有关。

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.