Increased ischemia-reperfusion blood flow impairs the skeletal muscle contractile function

Background. The ultimate aim of replantations and transplantations of skele tal muscle is to improve impaired function. The purpose of this study was t o examine the contribution of varying durations of ischemia to postischemic blood flow in the skeletal muscle and the contribution of modulation of po stischemic blood flow to skeletal muscle function and viability, using an i schemic revascularized hind limb model in rats. Materials and methods. Warm ischemia produced by vascular pedicle clamping was sustained for 90 min, 3 h, or 6 h. Postischemic blood how was measured by a Doppler flowmeter or microsphere technique. In another series of exper iments of 3-h ischemia, either saline or N-G-methyl-L-arginine acetate (L-N MMA) was infused for the first 2 h of reperfusion. Postischemic blood flow was also measured. Muscle contractile function and viability were determine d after 24 h of reperfusion. Results. Postischemic blood how was significantly increased during the firs t 10 min of reperfusion in the 90-minute ischemic group and during the firs t 2 h in the 3-h ischemic group compared with contralateral control blood h ow. No significant increase in postischemic blood how was noted in the 6-h ischemic group. Postischemic blood flow was significantly decreased by the L-NMMA infusion. Contractile function and viability of the tibialis anterio r muscle and contractile function of the gastrocnemius muscle in the L-NMMA group were significantly increased. Conclusion. Reperfusion blood how increased time dependently until 3 h of w arm ischemia. Hyperemia deteriorated skeletal muscle contractile function, although it was well preserved by L-NMMA infusion to restrict the postische mic hyperemia. (C) 2001 Academic Press.