Transcapillary forces and the development of oedema in the lower limb of patients with chronic critical limb ischaemia (CLI)

Abstract

Objective: factors regulating transcapillary fluid transport were investigated to elucidate the causes of oedema in CLI.

Material: sixteen patients, 6 men and 10 women (mean age of 79+/-10.3 years) with unilateral CLI and peripheral pitting oedema.

Methods: measurements were performed in both limbs. Interstitial fluid was collected by applying blister suction cups on the dorsolateral part of the foot and colloid osmotic pressure of this fluid (COP if) was measured in a colloid oncometer. Plasma colloid osmotic pressure (COP pl) was obtained from venous blood. Interstitial fluid pressure (P if) was measured by wick-in-needle technique.

Results: mean COP if in the limbs with CLI was 2.3 S.D. 0.5 mmHg, significantly lower than in the limbs without CLI (3.1 S.D. 0.7 mmHg, p<0.0001). Mean COP pl was 21.1 S.D. 1.8 mmHg, which was lower than in healthy controls. Mean plasma albumin concentration was 30 S.D. 6 g/l which was lower than the reference values. Mean P if in the limbs with CLI was 0.7 S.D. 1.6 mmHg, significantly higher than in the limbs without CLI (-1.4 S.D. 1.4 mmHg, p<0.0001). The calculated mean reabsorption pressure (P r) in the limbs with CLI was 19.6 S.D. 1.7 mmHg, significantly higher than in the contralateral limbs (16.7 S.D. 2.1 mmHg, p<0.001).

Conclusion: a low plasma albumin concentration in patients with CLI agrees with the reduction in COP pl but cannot explain the oedema formation, since it is unilateral. The high P r may cause a high transcapillary filtration pressure, resulting in a relatively great net filtration and subsequent oedema formation.