Isovolemic hemodilution and skeletal muscle function during ischemia and reperfusion.

Hemodilution has previously been shown to improve microcirculation in skeletal muscle after ischemia. We have studied the effects of isovolemic hemodilution with dextran on the function of anterior tibial muscle in the rabbit. Hemodiluted (hematocrit 28%) and nonhemodiluted animals were compared. Hemodilution led to an immediate increase in femoral blood flow. Flow normalized within 1-2 h, possibly due to flow redistribution. Hemodilution increased muscle force by 10%, which can reflect alterations in blood chemical composition or an improved microcirculation. Unilateral hindlimb ischemia induced by arterial occlusion inhibited muscle force to less than 15% in 150 min. Force and blood flow recovered almost completely after ischemia. After longer ischemia (170-300 min) when force was <5%, muscles did not recover. Hemodilution did not alter the muscle force or the extent or rate of force recovery after ischemia, which shows that the increased blood flow and improved microcirculation are not directly associated with changes in the sensitivity of muscle function to ischemia.