Background: Many of chronic critical limb ischaemia (CLI) patients have distal leg and foot oedema. Previous electronmicroscopic studies have shown that chronic severe ischaemia may cause hypoxic damage of the capillary endothelium, including morphological changes i.e. multiplicated/thickened basal lamina, and formation of interendothelial gaps. To assess the functional consequences of these morphologic derangements, where proteins can leak through, we investigated the composition of the interstitial fluid in oedematous ischaemic limbs.
Patients and methods: Nine female and 3 male patients with a mean age of 79 +/- 7.9 years were included. All had unilateral CLI and peripheral pitting oedema. Leg and foot volume was measured with water displacement volumetry. Blister suction technique was used to collect subcutaneous interstitial fluid. The concentration of albumin, transferrin, immunoglobulin G and alpha 2-macroglobulin in plasma and blister fluid was measured by immunoturbidimetry. Nine patients, 8 women and 1 man with a mean age of 83 +/- 5.5 years with a proximal femur fracture served as an age-matched control group.
Results: The mean concentration of albumin in blister fluid was significantly lower in the patients, whereas the mean concentration of alpha 2-macroglobulin in blister fluid did not differ between patients and controls. Mean ratio between concentrations in blister and serum of albumin, transferrin and immunoglobulin G in the limbs with CLI and oedema were significantly lower than respective values in the control group. However, there was no significant difference in the ratio of alpha 2-macroglobulin between these groups.
Conclusion: A higher transcapillary concentration gradient for proteins in CLI limbs signifies an increase in the net osmotic pressure gradient across the capillary wall, which may be a potential oedema limiting factor.