Model for skeletal muscle ischemia in rat hindlimb: evaluation of reperfusion and necrosis.

In this study we describe a technique for complete arrest of blood flow in rat hindlimbs. After graded periods of ischemia, immediate reperfusion in the leg was demonstrated by direct microscopy and scintigraphy. Laser Doppler flowmetry indicated microvascular hypoperfusion in the anterior tibial muscle during the first 2 h of reperfusion. The extent and distribution of necrosis in the middle part of the anterior tibial muscle of the legs were determined histologically 3 days after the ischemic insult. We found a reproducible degree of necrosis under constant experimental conditions. The necrosis was most pronounced in the central part of the muscle, leaving the subfascial fibers undamaged. After 4.0 h of ischemia, 46% of the cross-section area was necrotic. After 4.5 h, the necrosis increased to 70%. This difference was significant. Two types of necrotic zones were detected. One type was characterized by numerous macrophages and partial resorption of the muscle fibers, the other by a lack of macrophages and no resorption. Most cases with little damage had only the first type of necrosis, while most cases with extensive damage had both types. The areas that had no signs of resorption and therefore had been without circulation during most of the postischemic period, measured 8% after 4.0 h of ischemia and 22% after 4.5 h.