Reversible changes of skeletal muscular capillaries after application of a tourniquet.

Morphological studies of skeletal muscular capillaries after a 60-min tourniquet application were performed in the rat extensor hallucis proprius muscle. On the basis of the period of reflow, the rats were divided into three groups (15-min group, 24-hr group, and 7-day group). FITC-albumin was injected intravenously to detect open capillaries. The percentage of interstitial space of the muscle was high in the 24-hr group, but had recovered in the 7-day group. Capillary density, calculated under a fluorescence microscope, was low in both the 15-min and 24-hr groups, but in the 7-day group, it had recovered. Intramuscular pressure was high in the 15-min group, whereas it was almost normal in the 7-day group. Electron microscopic studies showed stenosis or collapse of the capillaries in the 15-min group, whereas it was almost normal in the 7-day group. We consider that the changes in the microcirculatory system in the rat extensor hallucis proprius muscle after a 60-min tourniquet application are reversible.