Transcapillary forces in patients with lower limb ischemia

Abstract

Starling pressures (interstitial fluid pressure, plasma and interstitial fluid colloid osmotic pressures) were measured in subcutaneous tissue at the ankle in 20 healthy controls and 27 patients with lower limb atherosclerosis. Subcutaneous interstitial fluid pressure (P_if) of the leg was also measured in seven patients with arterial emboli of the lower limb. Interstitial fluid was collected by implantation of nylon wicks and P_if was measured by the ‘wick-in-needle’, technique.

The calculated reabsorption pressure (equal to capillary pressure if no net filtration occurs) was 18.3 mmHg in the group with atherosclerosis, which was higher than in controls (15.8 mmHg, P < 0.05).

Colloid osmotic pressure of interstitial fluid (COP_if) was significantly lower in patients with atherosclerosis than in controls (5.9 v. 9.2 mmHg). This finding in itself could make those patients more susceptible to edema formation postoperatively. On the other hand, there was no correlation between COP_if and ankle systolic blood pressure within the group of patients.

There was a slight, but statistically significant positive correlation between ankle systolic blood pressure and P_if in patients with lower limb atherosclerosis although mean P_if was not different from controls (-1.0 v. -0.8 mmHg). In patients with arterial emboli, however, P_if was lower (mean -4.5 mmHg).

Key Words:

• arterial occlusive disease
• colloid osmotic pressure
• interstitial fluid pressure
• wick method
• wick-in-needle technique