Effect of sympathetic inhibition on maximal muscle blood flow in the normal and atherosclerotic human leg.

The control of blood flow in skeletal muscle is incompletely understood, and for this reason the effect of sympathetic inhibition on muscle blood flow in the leg was studied. One group of patients selected for study comprised 20 patients without evidence of vascular disease; a second comprised 20 with peripheral occlusive arterial disease, in whom the site of occlusion varied from the aorta to the lower leg arteries. None had undergone previous vascular surgery or sympathectomy. Variables studied included resting muscle blood flow; maximal muscle blood flow; interval from tourniquet release to onset of peak flow; duration of peak blood flow; muscle blood flow after tourniquet release; and skin temperature in the foot. Muscle blood flow was calculated from xenon-133 clearance. The variables were studied before and after ischemic (thigh tourniquet) and before and after sympathetic inhibition (immersion of hands and wrists in water at 45 degrees C). The significant differences between the two groups related to peak flow after ischemic exercise, the interval from tourniquet release to peak flow and duration of peak flow. Sympathetic inhibition was followed by no significant changes in maximal muscle blood flow, though there was a significant decrease in resting muscle blood flow. The results of the present study, in which noninvasive sympathetic blockade was used, confirm the findings of others that muscle blood flow does not change after operative sympathectomy.