The autotransfusion effect of external leg counterpressure in simulated mild hypovolemia.

We examined the cardiovascular response of external leg counterpressure in healthy volunteers at 100 mm Hg compression pressure. To stimulate mild hypovolemia, measurements were made with the subjects in a 60 degrees head-up tilt position. Left ventricular end-diastolic volume (LVEDV) and cardiac output (CO) were calculated from two-dimensional echocardiography. Flow through the inferior vena cava (IVC) below the origin of the hepatic veins was determined by the Doppler ultrasound technique. The application of counterpressure significantly increased LVEDV, CO, and arterial blood pressure over that seen with tilting without the device. These responses were accompanied by a small but significant increase in IVC flow. We therefore concluded that external leg counterpressure transferred blood to the central circulation by compression of the venous capacitance vessels (an autotransfusion effect) in mild hypovolemia, but such an effect may not benefit patients in a hypovolemic shock state because of the small amount of translocated blood.