COMPARISON OF THE MICROVASCULAR RESPONSE TO TRANSCUTANEOUS ELECTRICALNERVE-STIMULATION AND POSTOCCLUSIVE ISCHEMIA IN THE DIABETIC FOOT

Neurogenic inflammation, mediated by unmyelinated C-nerve fibers, is p art of the acute neurovascular response to injury. Laser doppler flowm etry was used to measure the flare response to transcutaneous electric al nerve stimulation (TENS) and to compare this axon reflex vasodilata tion with postischemic hyperemia in the skin of the foot in diabetic a nd nondiabetic subjects. Twenty-one control subjects and 57 diabetic p atients (25 type I; 32 type II; 14 without complications; 14 with neur opathy and without retinopathy; 8 with retinopathy and without neuropa thy; 21 with neuropathy and retinopathy) were enrolled in the study. F ollowing TENS, an increase in skin blood flow was found at the dorsum of the foot without any significant difference between the different g roups. Compared to the control group, axon reflex vasodilatation was s ignificantly reduced in the group of patients with diabetic neuropathy and in the group of patients with diabetic neuropathy and retinopathy at the pulp of the hallux (61 +/- 15 versus -6 +/- 16; versus 23 +/- 5; p < 0.05, respectively). All investigated groups exhibited a signif icant increase in skin blood flow after arterial occlusion without any significant difference between the groups. A good association was obs erved between postocclusive and TENS-induced hyperemia at the dorsum o f the foot (r = 0.39; p = 0.0002), but only a weak association was fou nd at the pulp of the hallux (r = 0.24; p = 0.03). TENS-induced hypere mia was associated with a diminished sweat response (p = 0.03), but no t with pathological cardiovascular function tests (p = 0.07). Electric al axon reflex vasodilatation is diminished in diabetic patients suffe ring from peripheral autonomic C-fiber injury, especially in skin rich in thermoregulatory blood flow. The diminished neurovascular response is independent of vascular alterations in diabetes mellitus. (C) 1997 Elsevier Science Inc.