Haemoconcentration and accumulation of white cells in the feet during venous stasis.

In experiments on eight healthy human subjects changes in the composition of the venous blood leaving the foot were examined during a 45-min period of sitting. Each subject reclined for 30-min before sitting with the foot approximately 1 m below the heart. Fluid filtration from the plasma into the tissues during sitting raised the haematocrit from an initial value of 41 +/- 0.6% to 49 +/- 1% after 20-min and to 51 +/- 1.5% at 40-min. The corresponding increase in plasma protein concentration was from 6.5 +/- 0.1 gdl-1 to 8.0 +/- 0.2 gdl-1 after 20 min and to 9.0 +/- 0.3 gdl after 40-min of sitting. Plasminogen activator levels in the foot venous blood during sitting were raised two to three fold over those found in venous blood taken from the arm at the start of the experiment. By contrast, after 20 min of sitting, white cell count of the venous blood of the foot was unchanged from the initial value of 7.4 +/- 0.8 X 10(-9) l-1 and increased to only 7.8 +/- 0.9 X 10(-9) l-1 at 40-min. This was in spite of an increase in the number of circulating white cells which, in blood taken from the arm at 45-min, had risen to 8.3 +/- 0.8 X 10(-9) l-1. The venous blood leaving the feet also failed to show an increase in platelet numbers. It is argued that approximately 15-20% of the white cells entering the feet during quiet sitting, do not leave in the venous blood. The possible significance of the results to the pathophysiology of venous hypertension is discussed.