Transcapillary filtration in lower limbs with deep venous thrombosis; the role of the capillary filtration coefficient.

The capillary filtration coefficient (CFC) of the Starling equation was measured with strain gauge plethysmography at calf level of lower limbs with deep venous thrombosis (DVT). CFC was significantly elevated in limbs with DVT compared to the contralateral limb (0.0037(0.0005) ml min-1 100 g-1 mmHg-1 rise in filtration pressure and 0.0026(0.0010) ml min-1 100 g-1 mmHg-1 rise in filtration pressure, p less than 0.01) (Mean(SD]. Calf blood flow was also measured with strain-gauge plethysmography and was significantly increased in limbs with DVT compared to the contralateral (2.9(1.4)ml min-1 100 g-1 and 2.3(1.4) ml min-1 100 g-1, p less than 0.05). Increased venous pressure (Pv) found in lower limbs with DVT could be expected to lead to reduced blood flow. Our results point to an inflammatory reaction over-ruling increased venous resistance. No correlation was found between CFC and blood flow but this may have methodological explanations since increased Pv will influence both CFC and blood flow recordings obtained with plethysmography. Interstitial fluid hydrostatic pressure (Pif) measured with the 'wick-in-needle' technique in the deep posterior muscle compartment was significantly increased compared to the contralateral limb (6.3(3.5) mmHg and -1.2(3.4) mmHg, p less than 0.001). No correlation was found between CFC and Pif. Increase in CFC and blood flow at calf level is probably important in oedema in lower limbs with DVT.