Torres Filho I P, Boegehold M A, Bouskela E, House S D, Johnson P C
Department of Physiology, University of Arizona College of Medicine, Tucson 85724.
Am J Physiol. 1989 Nov;257(5 Pt 2):H1647-55. doi: 10.1152/ajpheart.1989.257.5.H1647.
The purpose of this study was to examine changes in the microcirculation that might explain the rise in vascular resistance during hemorrhagic hypotension. Diameter and red blood cell velocity of microcirculatory vessels in exteriorized cat sartorius muscles were studied during 4 h of hemorrhagic hypotension at 60 mmHg. During hypotension, vascular resistance of the muscles rose approximately 70% while calculated volume flow in arterioles and venules fell to about the same degree. Average red blood cell velocity for all capillaries showed a comparable decline. Red blood cell flow stopped in approximately 60% of capillaries, but the extent of stoppage varied greatly among capillary fields. Arterioles larger than 45 microns constricted 9-29%, with the largest arterioles showing the greatest constriction. Arterioles smaller than 45 microns dilated 34-56%, with the smallest arterioles showing the greatest dilation. Venular diameter did not change with hemorrhage. The predominance of arteriolar dilation, especially in the later stages of hypotension, should lead to a fall in vascular resistance of the muscle. This effect may be offset by constriction of arteries outside the microcirculatory field observed and blockage of capillaries or venules by formed elements.
本研究的目的是检测微循环的变化，这些变化可能解释出血性低血压期间血管阻力的升高。在60 mmHg的出血性低血压4小时期间，对暴露的猫缝匠肌微循环血管的直径和红细胞速度进行了研究。在低血压期间，肌肉的血管阻力上升了约70%，而计算得出的小动脉和小静脉中的容积流量下降到大致相同的程度。所有毛细血管的平均红细胞速度也出现了类似的下降。约60%的毛细血管中红细胞流动停止，但毛细血管区域内的停止程度差异很大。直径大于45微米的小动脉收缩了9% - 29%，其中最大的小动脉收缩程度最大。直径小于45微米的小动脉扩张了34% - 56%，其中最小的小动脉扩张程度最大。小静脉直径并未随出血而改变。小动脉扩张占主导，尤其是在低血压后期，这应会导致肌肉血管阻力下降。这种效应可能会被观察到的微循环外动脉的收缩以及有形成分对毛细血管或小静脉的阻塞所抵消。
