Spatial variation of the veno-arteriolar reflex (VAR) and effect of reconstructive surgery in limbs with chronic critical limb ischaemia (CLI)

 

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Abstract

Ischaemic ulcers and necrosis tend to appear first in the most distal part of the feet in patients with chronic critical limb ischaemia (CLI), indicating that derangements in local microcirculation are focally distributed. In the present study the veno-arteriolar response (VAR), as an indicator of microcirculatory regulation, was obtained in three different areas of critically ischaemic feet. Five women and seven men, mean age 75 years, with unilateral CLI were included. Two groups including young and age-matched healthy participants served as controls. Laser Doppler flux (LDF) was recorded simultaneously at the pulp of the first toe (site 1), the level of the second metatarsal body (site 2), and the anterolateral part of the ankle (site 3). LDF was recorded with the investigated limb in supine and dependent positions. Orthostatic response (OR) was calculated at all measuring sites as perfusion (LDF) in the dependent foot divided by perfusion in the supine position. There was no difference in OR between the control groups, or between sites within each group. Median OR was about 0.5, indicating that perfusion was reduced to 50% during dependency. In patients with CLI, VAR was not present in the afflicted foot and ankle, and OR at the three sites were significantly greater than in controls (p < 0.0005). Median OR at site 1 was 3.7, indicating considerably increased local perfusion when the foot was lowered. At site 2 the increase was moderate, and there was no increase present at site 3 (median OR=1.0). There was a significant trend towards normal values (OR < 0.8) after vascular reconstruction at all sites. Abolished VAR and increased local perfusion in ischaemic limbs assist in explaining why patients with ischaemic rest pain obtain relief of pain with dependency. The recovery of VAR following reconstructive surgery indicates that the microcirculatory derangement is reversible.