To investigate vascular responses in insulin-dependent diabetic patients both with and without retinopathy, we have assessed vasodilation by forearm transcutaneous pO2 measurement after 10 min of ischemia produced by a sphygmomanometer cuff. Diabetic patients with proliferative retinopathy had a delayed vasodilatory response at 60 s (mean ± SD pO2 = 9 ± 3 mm Hg) compared with those having diabetes without retinopathy (15 ± 4 mm Hg, P < 0.01) and matched normal subjects (14 ± 4 mm Hg, P < 0.01). Recently diagnosed insulin-dependent diabetic patients had a very similar response (15 ± 5 mm Hg) to matched normal subjects (15 ± 3 mm Hg). The diminished vascular reactivity may be a consequence of microangiopathy and neuropathy, although patients with an impaired vascular response might be particularly at risk from the development of capillary closure.

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