Skin microvascular blood flow control in long duration diabetics with and without complications.

The integrity of the regulation of skin microvascular blood flow has been studied in Type 1 diabetic patients with and without clinical evidence of microvascular complications after a long duration of diabetes. 13 uncomplicated patients with a mean duration of diabetes of 38 +/- 6 (SD) yr were compared with 10 patients with proliferative retinopathy and a group of healthy control subjects. Using laser Doppler flowmetry 2 distinct microvascular responses were examined in the skin of the finger: (a) reactive hyperaemia following the release of one minute's digital arterial occlusion, a response that is independent of neural mechanisms, and (b) the fall in skin blood flow on venous occlusion that occurs due to the veno-arteriolar reflex, a response that depends upon intact local sympathetic nervous function. The duration of reactive hyperaemia was longer in the complicated patients than either the group without complications (69 +/- 38: 23 +/- 17 s, p less than 0.01) or the healthy controls (27 +/- 20 s, p less than 0.05). In contrast the percentage fall in laser Doppler blood flow on venous occlusion was significantly less (p less than 0.01) in both diabetic groups than that achieved in healthy controls, (50 +/- 14% controls; 26 +/- 12% uncomplicated group; 28 +/- 12% patients with retinopathy). There was no difference in current or recent diabetic control in the 2 diabetic groups. These results suggest that some degree of sympathetic neuropathy is almost inevitable after a long duration of Type 1 diabetes.(ABSTRACT TRUNCATED AT 250 WORDS)