DIFFERENCES IN FOOT AND FOREARM SKIN MICROCIRCULATION IN DIABETIC-PATIENTS WITH AND WITHOUT NEUROPATHY

OBJECTIVE - We have compared the hyperemic response to heal and the en dothelium-dependent and endothelium-independent vasodilatation between the dorsum of the foot and the forearm in diabetic neuropathic and no n-neuropathic patients and healthy control subjects. RESEARCH DESIGN A ND METHODS - We studied the cutaneous microcirculation in the forearm and foot in 15 diabetic patients with neuropathy, in 14 diabetic patie nts without neuropathy, and in 15 control subjects matched for age, se x, BMI, and in the case of diabetic patients, for the duration of diab etes. Patients with peripheral vascular disease and/or renal impairmen t were excluded. The cutaneous microcirculation of the dorsum of the f oot and the flexor aspect of the forearm was tested in all subjects. S ingle-point laser Doppler was employed to measure the maximal hyperemi c response to heating of the skin to 44 degrees C and laser Doppler im aging scanner was used to evaluate the response to iontophoresis of 1% acetylcholine chloride (Ach) (endothelium-dependent response) and 1% sodium nitroprusside (NaNP) (endothelium-independent response). RESULT S - The transcutaneous oxygen tension was lower in the neuropathic gro up at both foot and forearm level, while the maximal hyperemic respons e to heat was similar at the foot and forearm level in all three group s. The endothelium-dependent vasodilatation (percent increase over bas eline) was lower in the foot compared to the forearm in the neuropathi c group (23 +/- 4 vs. 55 +/- 10 [mean +/- SEM]; P < 0.01)], the non-ne uropathic group (33 +/- 6 vs. 88 +/- 14; P < 0.01), and the control su bjects (43 +/- 6 vs. 93 +/- 13; P < 0.001). Similar results were obser ved during the iontophoresis of NaNP (P < 0.05). No differences were f ound among the three groups when the ratio of the forearm:foot respons e was calculated for both the endothelium-dependent (neuropathic group , 2.25 +/- 0.24; non-neuropathic group, 2.55 +/- 0.35; and control sub jects, 2.11 +/- 0.26; P = NS) and endothelium-independent vasodilatati on (neuropathic group, 1.54 +/- 0.27; non-neuropathic group, 2.08 +/- 0.33; and control subjects, 2.77 +/- 1.03; P = NS). The vasodilatory r esponse, which is related to the C nociceptive fiber action, was reduc ed at the foot level during iontophoresis of Ach in the neuropathic gr oup. In contrast, no difference was found during the iontophoresis oi NaNP at the foot and forearm level and of Ach at the forearm level amo ng all three groups. CONCLUSIONS - In healthy subjects, the endothelia l-dependent and endothelial-independent vasodilatation is lower at the foot level when compared to the forearm, and a generalized impairment of the microcirculation in diabetic patients with neuropathy preserve s this forearm-foot gradient. These changes may be a contributing fact or for the early involvement of the foot with neuropathy when compared to the forearm.