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, doe s this increased anastomotic shunt flow lead to either under- or overp erfused nutritive capillaries. 2. To solve this question, skin microci rculation tests of the left big toe were performed in 20 healthy subje cts and in 40 insulin-dependent patients without macroangiopathy, 20 w ithout and 20 with neuropathy. Skin temperature measurements and laser Doppler fluxmetry were performed to record mainly shunt flow and capi llaroscopy to study nailfold capillary blood flow. 3. The insulin-depe ndent diabetic patients with neuropathy had a higher baseline skin tem perature (mean+/-SEM; 30.0+/-0.6 degrees C) and laser Doppler fluxmetr y [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 con trol 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 lase r Doppler fluxmetry decrease in the neuropathic patients (31.4+/-4.6%) compared with non-neuropathic patients (48.2+/-5.1%, P <0.05) and con trol 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 mm(2)), when comp ared with non-neuropathic patients (8.7+/-1.2/0.5 mm(2), P <0.05) and control subjects (8.3+/-0.3/0.5 mm(2), 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+/-0.03mm/s, P <0.05) and control subjects (0.23+/-0.02 mm/s, P <0.01). 4. We conclu de that there is an overperfused nutritive capillary circulation in th e feet of patients with diabetic neuropathy, This is in contradiction to the capillary steal phenomenon and favours the hyperdynamic hypothe sis to explain the decreased healing potential in diabetic neuropathic foot ulceration.