EFFECTS OF GRADED HYPOTENSION ON CEREBRAL BLOOD-FLOW, BLOOD-VOLUME, AND MEAN TRANSIT-TIME IN DOGS
EFFECTS OF GRADED HYPOTENSION ON CEREBRAL BLOOD-FLOW, BLOOD-VOLUME, AND MEAN TRANSIT-TIME IN DOGS
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DOI：
10.1152/ajpheart.1992.262.6.h1908
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发表时间：
1992-06-01
影响因子：
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通讯作者：
TRAYSTMAN, RJ
中科院分区：
文献类型：
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作者：
FERRARI, M;WILSON, DA;TRAYSTMAN, RJ
这项研究检验了脑血流量（CBF）通过血管舒张维持的假设，其表现为当脑灌注压降低时平均通过时间（MTT）和脑血容量（CBV）逐渐增加。通过控制出血，10 只戊巴比妥麻醉犬的脑灌注压降低。微球测定的 CBF 在所有测试的大脑区域在 40 至 130 mmHg 脑灌注压范围内自动调节，但在大约 30 mmHg 时下降 50%。在 40 至 130 mmHg 脑灌注压范围内，右侧顶叶大脑皮层的 MTT 和 CBV 逐渐按比例增加。通过光学方法在同一区域测量的总血红蛋白含量 (Hb(t)) 与计算为 (CBF.MTT) 乘积的 CBV 的增加平行增加。在 30 mmHg 脑灌注压下，CBV 和 Hb(t) 仍然增加，MTT 不成比例地延长（对照的 690%）。我们的结论是，在自动调节范围内，CBF 恒定性是通过增加 CBV 和 MTT 来维持的。在自动调节范围之外，MTT 会显着延长。当 CBV 最大时，脑灌注压的进一步降低会导致 MTT 不成比例地增加，这表明脑血管扩张血流动力学储备丧失。
This study tested the hypothesis that cerebral blood flow (CBF) is maintained by vasodilation, which manifests itself as a progressive increase in mean transit time (MTT) and cerebral blood volume (CBV) when cerebral perfusion pressure is reduced. Cerebral perfusion pressure was decreased in 10 pentobarbital-anesthetized dogs by controlled hemorrhage. Microsphere-determined CBF was autoregulated in all tested cerebral regions over the 40- to 130-mmHg cerebral perfusion pressure range but decreased by 50% at approximately 30 mmHg. MTT and CBV progressively and proportionately increased in the right parietal cerebral cortex over the 40- to 130-mmHg cerebral perfusion pressure range. Total hemoglobin content (Hb(t)), measured in the same area by an optical method, increased in parallel with the increases in CBV computed as the (CBF.MTT) product. At 30 mmHg cerebral perfusion pressure, CBV and Hb(t) were still increased and MTT was disproportionately lengthened (690% of control). We conclude that within the autoregulatory range, CBF constancy is maintained by both increased CBV and MTT. Outside the autoregulatory range, substantial prolongation of the MTT occurs. When CBV is maximal, further reductions in cerebral perfusion pressure produce disproportionate increases in MTT that signal the loss of cerebral vascular dilatory hemodynamic reserve.