The veno-arteriolar reflex in venous leg ulcer patients studied by laser Doppler imaging

Posture-induced microcirculatory changes in the lower leg were studied in venous leg ulcer patients and in control subjects by means of laser Doppler imaging (LDI), a technique which allows almost real-time mapping of the perfusion from a distance, each perfusion value constituting the mean of a number of measurements at separate sites. LDI values for intact skin with the subject supine were 0.39 (0.32, 0.47) V [geometric mean (gm -SD, gm +SD)] and 0.32 (0.15, 0.70) V in two age groups of controls and 0.91 (0.66, 1.24) V in patients (NS). Values were 2.04 (1.25, 3.35) V for skin at the ulcer margin, and 1.44 (0.72, 2.88) V in the ulcer proper. With the lower leg passively dependent, lower LDI values were obtained at all sites in all groups, the reduction in intact skin value being 62 +/- 11% (arithmetic mean +/- SD) (p < 0.01) in the younger controls, 43 +/- 24% (p < 0.01) in the older controls and 62 +/- 19% (p < 0.001) in the patient group, and the reduction in ulcer values being 45 +/- 27% (p < 0.05) for the margin and 52 +/- 23% (p < 0.001) for the ulcer proper. Thus, a high degree of postural vasoconstriction was present overall, even in the ulcer itself. Vasomotor tone in the skin of the lower leg was assessed by topical application of methyl nicotinate, a vasodilator. The skin perfusion value (supine position, no stimulus) was 71 +/- 31% (p < 0.01) of the drug-induced (assumed peak) hyperaemia value [0.60 (0.30, 1.10) V] in patients and 24 +/- 25% (p < 0.001) of the hyperaemia value (1.30 (0.64, 2.62) V] in the controls. It would appear that in ulcer patients the veno-arteriolar reflex, despite being comparable in magnitude to that in controls, may nonetheless be insufficient to reduce tone during dependency to a level similar to that in healthy controls.