Pressure Pulse Transmission Ratio (PPTR) of Inferior Vena Cava and the Blood Volume Status

Abstract

Estimation and correction of circulatory blood volume during surgery are the major parts of anesthesiologists’ interest. However, clinical observation are apparently subjective and misleading in some cases, while no objective and quantitative method of monitoring have been successfully established. Of the many studies concerning on the venous pressure, few were focused on the venous pressure pulsatility, and none of them was related to blood volume status. The venous pressure pulse waves, generated mainly in the right atrium as a result of cardiac pumping, are transmitted distally along the inferior vena cava. During the transmission, the waves are modified, and both the shape and the amplitude changes. It seems apparent that this modification is affected by the physical properties of the vein along which the waves were transmitted. If so, monitoring the magnitude of such modification to the pressure pulsatility can be expected to help observing the physical properties of the corresponding vein, thus leading to more accurate assessment of the blood volume status. The authors examined the changes of the pressure pulse sizes recorded at two large veins; central vein and abdominal inferior vena cava during surgery, in relation to the estimated amount of blood loss.