PERIWOUND SKIN MICROCIRCULATION OF VENOUS LEG ULCERS

Chronic venous ulceration has an estimated prevalence of from 0.06 to 1.3% with about 57 to 80% of patients with leg ulcers having demonstra ble venous disease, The sequence of events whereby chronic venous insu fficiency leads to leg skin ulceration is not yet worked out. Venous h ypertension may set the stage for subsequent ulcer development via lin kages to observed changes in skin microvessel metrics, morphology, the ology, permeability, hemodynamics, and the interstitium. Periulcer mea surements show decreased transcutaneous oxygen and elevated carbon dio xide tensions, yet the skin blood perfusion measured with laser Dopple r fluxometry (LDF) is reported to be elevated. This elevated perfusion , (Q), could be due to independent changes in blood velocity (U), and volume (V), with different mechanistic implications depending on the m ode. Thus, we sought to determine the relative contributions of these two components with the aim of clarifying the mechanism responsible fo r the reported skin flow changes. Patients studied (n = 16) had unilat eral venous ulcers, an ankle/brachial BP index >0.8, and venous pathol ogy demonstrated by duplex imaging. Ulcer areas ranged from 0.6 to 76. 9 cm(2) (mean = 13.7 cm(2)) and were present for 2 to 144 months, mean = 32. With the patient supine, Q (ml/min/100 g), V (%), and U (mm/sec ) were measured by LDF (Vasamedics, BPM403A) at two to three sites on periulcer skin and compared with measurements at corresponding sites o n the nonulcerated limb at local skin temperatures of 35 and 44. Resul ts confirm an elevation in basal periulcer flow (7.0 vs 1.8 ml/min/100 g, P = 0.001) and show this to be due to elevations in both circulati ng blood volume (1.24 vs 0.62%, P < 0.001) and velocity (1.23 vs 0.65 mm/sec, P =.004). Maximal Q, V, and U were also higher on the ulcer le g, being for Q, 11.2 vs 6.42 ml/min/100 g, P = 0.03; for V, 1.49 vs 1. 13%, P = .002; and for U, 1.76 vs 1.33 mm/sec, P = 0.020. Expressing e ach leg's basal values as a percentage of its own maximal response sho ws the ulcerated leg to have higher values for Q, V, and U, with (ulce r leg/control leg) ratios being 2.5, 1.8, and 1.4, respectively. These findings show that the LDF perfusion increase is due to roughly equal increases in microvessel circulating blood volume and velocity. Based on the present functional data and the preponderance of in vivo micro vessel changes reported in the literature, a plausible and consistent characterization of the periulcer tissue is one of a tissue in which t he number of microvessels is reduced, with the remaining ones carrying a greater blood volume at an increased blood velocity. (C) 1994 Acade mic Press, Inc.