Right atrial pressure and venous return during cardiopulmonary bypass

The relevance of right atrial pressure (RAP) as the backpressure for venous return (QVR) and mean systemic filling pressure as upstream pressure is controversial during dynamic changes of circulation. To examine the immediate response of QVR (sum of caval vein flows) to changes in RAP and pump function, we used a closed-chest, central cannulation, heart bypass porcine preparation (n = 10) with venoarterial extracorporeal membrane oxygenation. Mean systemic filling pressure was determined by clamping extracorporeal membrane oxygenation tubing with open or closed arteriovenous shunt at euvolemia, volume expansion (9.75 ml/kg hydroxyethyl starch), and hypovolemia (bleeding 19.5 ml/kg after volume expansion). The responses of RAP and QVR were studied using variable pump speed at constant airway pressure (PAW) and constant pump speed at variable PAW. Within each volume state, the immediate changes in QVR and RAP could be described with a single linear regression, regardless of whether RAP was altered by pump speed or PAW (r2 = 0.586–0.984). RAP was inversely proportional to pump speed from zero to maximum flow (r2 = 0.859–0.999). Changing PAW caused immediate, transient, directionally opposite changes in RAP and QVR (RAP: P ≤ 0.002 and QVR: P ≤ 0.001), where the initial response was proportional to the change in QVR driving pressure. Changes in PAW generated volume shifts into and out of the right atrium, but their effect on upstream pressure was negligible. Our ...
Source: AJP: Heart and Circulatory Physiology - Category: Cardiology Authors: Tags: RESEARCH ARTICLE Source Type: research