Pathophysiology of Hypermia and Effects of Reducing Blood Flow at the Immediate Post-Ischemia in the Brain.

已知在短暂性脑缺血再灌注期，脑血流量较缺血前显着增加。虽然这种缺血后充血可以发生在临床情况下，如脑血管手术，但这种现象的病理生理学意义和抑制充血的治疗措施的效果都没有得到广泛的研究。因此，我们研究了脑缺血后即刻控制性降压对脑血流量、血脑屏障功能和神经学结局的影响。(方法)27只成年猫麻醉机械通气后，在手术显微镜下经眶入路暴露大脑中动脉。在第一组实验中，记录局部脑血流量(氢气清除法)、细胞外钾离子(Kec；静电计技术)和脑电，同时闭塞大脑中动脉进行…。三个多小时，然后释放了两个小时。再灌流2小时后，计算固定脑片的伊文思蓝穿透指数。在第二系列实验中，在脑缺血3小时后48小时对神经功能缺失进行评分。两组动物均按再灌流时血流动力学处理方法分组，无特殊对照=A，A‘，氟烷对照=B，B’，戊巴比妥钠对照=C，C‘。(结果)与A/A‘组相比，B/B’和C/C‘组平均动脉压降低20~35 mm Hgin。然而，两组间缺血后rCBF差异无统计学意义。A、B、C组平均伊文思蓝穿透指数分别为232、93、26。A、C两组比较，差异有统计学意义。神经功能缺失评分A‘组明显高于B’和C‘组。(讨论)这些结果表明，控制性降压的血流动力学管理减少了血浆蛋白的穿透，从而减少了短暂性脑缺血后再灌流时血管源性脑水肿的发生。诱导性低血压也改善了神经学结果。然而，充血反应并不总是通过降低全身血压而被抑制。需要进一步的研究来阐明即刻再灌流时血压和rCBF的关系以及其他降压药或低碳酸血症的影响。较少

It has been known that during a reperfusion period following transient ischemia cerebral blood flow remarkably increases from the pre-ischemic level. Although this post-ischemic hyperemia can occur in clinical situations such as cerebrovacs ular surgery, neither pathophysiologic significance of this phenomenon nor effects of therapeutic measures to suppress hyperemia have been extensively studied. Therefore, we examined the influences of induced hypotension during the immediate post-ischemic period upon cerebral blood flow, blood-brain barrier function, and neurologic outcome. (Methods) The middle cerebral artery was exposed by a transorbital approach using a surgical microscope in 27 adult cats anesthetized and mechanically ventilated. In the first series of experiment, the regional Cerebral Blood Flow (rCBF ; hydrogen clearance method), extracellular potassium ion (Kec ; electrometer technique), and electroencephalogram were recorded, while the middle cerebral artery was occluded for … More three hours and then released for two hours. Following a reperfusion period of two hours, Evans blue penetration index was calculated in slices of fixed brain samples. In the second series of experiment, neurologic deficits were scored at 48 hours after a 3 hours cerebral ischemia. In both series, animals were grouped according to the method of hemodynamic management at reperfusion ; without specific control=A, A', controlled with halothane=B, B', and controlled with pentobarbital=C, C'. (Results) Mean arterial blood pressure was significantly reduced by 20 to 35mmHgin groups B/B' and C/C', compared to groups A/A'. However, post-ischemic rCBF was not significantly different between groups. The mean Evans blue penetration index was 232, 93, and 26, in groups A, B, and C, respectively. The difference of the index between groups A and C was statistically significant. Neurological deficit score was significantly greater in group A' than in groups B' and C'. (Discussion) These results suggest that hemodynamic management by induced hypotension reduces penetration of plasma protein, and hence the development of vasogenic brain edema at reperfusion following a transient cerebral ischemia. Neurologic outcome was also improved by induced hypotension. However, hyperemic responses were not always suppressed by reduction of systemic blood pressure. Further studies were necessary to clarify the relationship between blood pressure and rCBF at the immediate reperfusion and the effects of other hypotensive agents or hypocapnia. Less