Blood volume distribution in the Trendelenburg position.

The Trendelenburg position is used frequently in treating hypotensive patients. It is believed that placing patients in the Trendelenburg position causes an autotransfusion of blood to the central circulation. No published studies document the volume of blood displaced centrally. In our study ten volunteers were placed in the Trendelenburg position. Blood volumes were determined from body surface area, and radionuclide scanning was used to determine blood volume distribution. Placing normovolemic volunteers in the Trendelenburg resulted in a 1.8% (median) displacement of the total volume centrally. The autotransfusion of blood produced by the Trendelenburg position is small and is unlikely to have an important clinical effect.