Skin microcirculation of the foot in diabetic neuropathy

1. In the feet of patients with diabetic neuropathy, total skin blood flow is increased due to an increased shunt flow. The question is, does this increased anastomotic shunt flow lead to either under- or overperfused nutritive capillaries. 2. To solve this question, skin microcirculation tests of the left big toe were performed in 20 healthy control subjects and in 40 insulin-dependent diabetic patients without macroangiopathy, 20 without and 20 with neuropathy. Skin temperature measurements and laser Doppler fluxmetry were performed to record mainly shunt flow and capillaroscopy to study nailfold capillary blood flow. 3. The insulin-dependent diabetic patients with neuropathy had a higher baseline skin temperature (mean +/- SEM; 30.0 +/- 0.6 degrees C) and laser Doppler fluxmetry [26.2 +/- 2.2 perfusion units (pu)] than patients without neuropathy (27.2 +/- 0.8 degrees C, P < 0.01; 16.1 +/- 2.0 pu, P < 0.01) and healthy control subjects (27.9 +/- 0.7 degrees C, P < 0.05; 18.6 +/- 2.8 pu, P < 0.05). Sympathetic stimulation (inspiratory gasp) resulted in a smaller laser Doppler fluxmetry decrease in the neuropathic patients (31.4 +/- 4.6%) compared with non-neuropathic patients (48.2 +/- 5.1%, P < 0.05) and control subjects (49.0 +/- 3.8%, P < 0.05), while no difference between the three groups was seen in the laser Doppler fluxmetry decrease during a postural vasoconstriction test. The number of visible capillaries was highest in the neuropathic patients (10.2 +/- 0.6/0.5 mm2), when compared with non-neuropathic patients (8.7 +/- 1.2/0.5 mm2, P < 0.05) and control subjects (8.3 +/- 0.3/0.5 mm2, P < 0.001). Capillary blood-cell velocity was significantly higher in the neuropathic patients (0.32 +/- 0.05 mm/s) compared with non-neuropathic patients (0.23 +/- 0.03 mm/s, P < 0.05) and control subjects (0.23 +/- 0.02 mm/s, P < 0.01). 4. We conclude that there is an overperfused nutritive capillary circulation in the feet of patients with diabetic neuropathy. This is in contradiction to the capillary steal phenomenon and favours the hyperdynamic hypothesis to explain the decreased healing potential in diabetic neuropathic foot ulceration.