Czosnyka M, Richards H K, Whitehouse H E, Pickard J D
MRC Cambridge Centre for Brain Repair, Addenbrooke's Hospital, Cambridge, England.
J Neurosurg. 1996 Jan;84(1):79-84. doi: 10.3171/jns.1996.84.1.0079.
Clinical studies with transcranial Doppler suggest that the pulsatility of the flow velocity (FV) waveform increases when the distal cerebrovascular resistance (CVR) increases. To clarify this relationship, the authors studied animal models in which the resistance may be decreased in a controlled manner by an increase in arterial CO2 tension, or by a decrease in cerebral perfusion pressure (CPP) in autoregulating animals. Twelve New Zealand white rabbits were anesthetized, paralyzed, and ventilated. Transcranial Doppler basilar artery FV, laser Doppler cortical blood flow, arterial pressure, intracranial pressure, and end-tidal CO2 concentration were measured continuously. Cerebrovascular resistance (CPP divided by laser Doppler cortical flux) and Gosling Pulsatility Index (PI, defined as an FV pulse amplitude divided by a timed average FV) were calculated as time-dependent variables for each animal. Four groups of animals undergoing controlled manipulations of CVR were analyzed. In Group I, arterial CO2 concentration was changed gradually from hypocapnia to hypercapnia. In Group II, gradual hemorrhagic hypotension was used to reduce CPP. In Group III, the short-acting ganglion blocking drug trimetaphan was injected intravenously to induce transient hypotension. Intracranial hypertension was produced by subarachnoid saline infusion in Group IV. During the hypercapnic challenge the correlation between the cortical resistance and Doppler flow pulsatility was positive (r = 0.77, p<0.001). In all three groups in which cerebral perfusion pressure was reduced a negative correlation between pulsatility index and cerebrovascular resistance was found (r = -0.84, p<0.001). The authors conclude that PI cannot be interpreted simply as an index of CVR in all circumstances.
经颅多普勒的临床研究表明，当远端脑血管阻力（CVR）增加时，血流速度（FV）波形的搏动性会增强。为了阐明这种关系，作者研究了动物模型，在这些模型中，通过提高动脉二氧化碳分压或降低自动调节动物的脑灌注压（CPP），可以以可控方式降低阻力。12只新西兰白兔被麻醉、麻痹并进行通气。连续测量经颅多普勒基底动脉FV、激光多普勒皮质血流、动脉压、颅内压和呼气末二氧化碳浓度。计算每只动物的脑血管阻力（CPP除以激光多普勒皮质血流量）和戈斯林搏动指数（PI，定义为FV脉冲幅度除以定时平均FV）作为随时间变化的变量。分析了四组接受CVR控制性操作的动物。在第一组中，动脉二氧化碳浓度从低碳酸血症逐渐变为高碳酸血症。在第二组中，采用逐渐出血性低血压来降低CPP。在第三组中，静脉注射短效神经节阻滞药物曲美芬以诱导短暂性低血压。在第四组中，通过蛛网膜下腔注入生理盐水产生颅内高压。在高碳酸血症激发期间，皮质阻力与多普勒血流搏动性之间的相关性为正（r = 0.77，p<0.001）。在所有三组脑灌注压降低的实验中，发现搏动指数与脑血管阻力之间呈负相关（r = -0.84，p<0.001）。作者得出结论，PI在所有情况下都不能简单地解释为CVR的指标。
