Reactive hyperemia as an indicator of peripheral vasodilation associated with arterial stenoses.

Reactive hyperemia occurs when an artery is temporarily occluded and the occlusion is then released. During a period of vascular occlusion, peripheral vascular dilatation develops distally, and is reversed only gradually after release of the occlusion. Reactive hyperemia was measured in the hind limbs of five mongrel dogs at different degrees of arterial stenosis to determine at what degree of stenosis compensatory vasodilatation of the peripheral vascular bed occurs. In the hind limbs of the dogs, which had been anesthetized, reactive hyperemia as an expression of peripheral vasodilatation did not occur until the critical stenosis (the stenosis at which resting flow started to drop) was reached. It began to occur only beyond the critical stenosis, and then increased as the vessel became totally occluded. This study contradicted the vasodilator reserve theory, which states that during progressive arterial stenosis the peripheral vascular bed dilates to maintain flow until the peripheral vascular bed is maximally dilated, when the critical stenosis is reached.