MEASUREMENT OF ANTERIOR-POSTERIOR DIAMETER OF INFERIOR VENA-CAVA BY ULTRASONOGRAPHY - A NEW NONINVASIVE METHOD TO ASSESS ACUTE CHANGES IN VASCULAR FILLING STATE

Objective: The aim was to determine whether measurement of the anterio r-posterior diameter of the inferior vena cava (IVC) by ultrasonograph y, before and during deep inspiration, allows indirect information on baseline blood volume and changes in vascular filling state to be obta ined in healthy subjects. Methods: Blood volume was measured in 12 vol unteers by a standard radioactive isotope method. The IVC dimensions w ere measured by ultrasound in various positions. In addition, in 10 ma le subjects the effect on the IVC dimensions of volume loading was eva luated by rapid infusion of plasma expander. During and immediately fo llowing volume loading, the IVC dimensions and blood volume were remea sured. Results: Neither the baseline IVC diameters nor any combination of these variables correlated with the concomitant blood volume. Volu me loading increased the anterior-posterior IVC dimensions linearly, t he largest increase being observed with the maximum IVC diameter and t he subject in supine position. Conclusions: It follows that ultrasonic IVC indices cannot be used as accurate indirect estimate of baseline blood volume, but provide reliable information on acute changes of the subjects' vascular filling state.