The venoarteriolar reflex in diabetic and other neuropathies.

Limb dependency activates the venoarteriolar reflex (VAR), resulting in reflex vasoconstriction (RV). Since others have reported the VAR to fail in diabetic neuropathy, we examined the reliability of this test in detecting sympathetic failure in diabetic and other neuropathies. We studied 40 controls, 49 diabetic subjects, and 29 patients with other neuropathies. The mean RV was greater in controls than in diabetics or other neuropathies, but there were marked overlaps among groups. We conclude that the VAR, while impaired in the neuropathies, is of little value as a clinical test and is a poorer test of autonomic function than the quantitative sudomotor axon reflex test or heart rate responses to deep breathing or the Valsalva maneuver.