Skeletal muscle microvascular and tissue injury after varying durations of ischemia

The purpose of this study was to examine the effect of varying durations of ischemia on several microvascular parameters in the awake hamster chamber model. The goal was to characterize the microvascular damage that occurs in skeletal muscle as a result of ischemia and reperfusion. The chamber tissues were subjected to 1-5 h of ischemia, and then the following parameters were measured: vessel diameter, endothelial thickness, macromolecular leakage, red blood cell velocity, adherent leukocytes, rolling leukocytes, freely flowing leukocytes, functional capillary density, and propidium iodide-positive cell nuclei. In control animals there was no significant difference in any parameters over the entire observation period. After 1 or 2 h of ischemia an increase in rolling and adherent leukocytes was measured. After 3 h of ischemia there was a significant increase in the mean endothelial thickness and in the number of nonviable cells. After 4 h of ischemia a significant difference in the extent of macromolecular leakage and the functional capillary density was additionally observed. After 5 h of ischemia this damage was more pronounced and often so severe that approximately 50% of the vessels demonstrated no reflow.