Alterations in the microcirculation during ischemiareperfusion

A compensatory hyperemia with vasodilatation can be observed following a relatively short duration of ischemic hypoxia. However, after a longer ischemic period, micro-vascular alterations develop and a reduction or complete cessation of the capillary perfusion is observed (no-reflow phenomenon). The point in time during the course of ischemia and reperfusion where tissue injury becomes irreversible is unknown.20 Microscopic studies demonstrate formation of edematous endothelial cells, rouleaux formation of erythrocytes, reduction of red blood cell deformability, arterial vasospasm and the formation of microthrombi.21, 22 During an experimental compartment syndrome, vasodilatation was followed by an intense vasoconstriction within the first hour.23 Moreover, over three hours following reperfusion, neutrophils were sequestered in the muscle circulation due to adhesion of neutrophils to the endothelium within post-capillary venules - a process that started within minutes.

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