Modifications of plasma levels of tissue factor pathway inhibitor and endothelin-1 induced by a reverse Trendelenburg position: influence of elastic compression--preliminary results.

PURPOSE The purpose of this study was to assess the effects of the passive 45-degree reverse Trendelenburg position and graduated compression stockings (GCS) on plasma tissue factor pathway inhibitor (TFPI) and endothelin-1 levels in a group of volunteers. METHODS Ten healthy subjects lay on an examining table for 30 minutes while baseline measurements were made. The table was then tilted to a 45-degree upright position for 60 minutes, and measurements were repeated. On a different day, subjects were tilted again, but on this occasion they wore thigh-length GCS. Blood was drawn before and 60 minutes after tilting during both sessions, and plasma TFPI and endothelin-1 were obtained. Cross-sectional areas of the calf medial gastrocnemius vein, before and after tilting, were measured by a duplex scanner. RESULTS Upright tilting induced a significant dilation of the medial gastrocnemius veins that was partially corrected by the use of elastic stockings. Similarly, endothelin-1 levels significantly increased after tilting. The use of GCS did not modify these differences. On the other hand, although TFPI levels were not affected by tilting without stockings, they were significantly elevated after tilting when GCS were used. CONCLUSIONS Upright passive tilting induces significant dilation of the deep calf veins and is associated with a significant increase in plasma levels of endothelin-1, whereas TFPI levels remain unchanged. The use of elastic stockings reduces the degree of calf distention but does not prevent an increase in endothelin-1. TFPI levels are significantly increased after tilting when GCS are used. This might represent a previously unknown mechanism of action of elastic stockings with interesting potential for deep vein thrombosis prophylaxis. More studies are warranted in a larger series to confirm these results.