Ventriculo-arterial uncoupling is associated with VO2 dependency in cardiac surgical patients

BackgroundThe clinical relevance of V-A (un)coupling in critically ill patients is under investigation. In this study we measured the association between V-A coupling and oxygen consumption (VO2) response in patients with acute circulatory instability following cardiac surgery.\n\nMethods and resultsSixty-one cardio-thoracic ICU patients who received fluid challenge or norepinephrine infusion were included. Arterial pressure, cardiac output (CO), heart rate (HR), arterial (EA), and ventricular elastances (EV), total indexed peripheral resistance (TPRi) were assessed before and after hemodynamic interventions. VO2 responders were defined as VO2 increase > 15 %. V-A coupling was evaluated by the ratio EA/EV. Left ventricle stroke work (SW) to pressure volume area (PVA) ratio was calculated. In the overall population, 24 patients (39%) were VO2 responders and 48 patients were uncoupled (i.e., EA/EV ratio > 1.3): 1.9 (1.6-2.4). Most of the uncoupled patients were classified as VO2 responders (28 of 31 patients, p=0.031). Changes in VO2 were correlated with those of TPRi, EA, EA/EV and CO. EA/EV ratio predicted VO2 increase with an AUC of 0.76 [95 % CI: 0.62-0.87]; p=0.001. In multivariate and principal component analyses, EA/EV and SW/PVA ratios were independently associated (P < 0.05) with VO2 response following interventions.\n\nConclusionsVO2 responders were characterized by baseline V-A uncoupling due to high EA and low EV. Baseline EA/EV and SW/PVA ratios were associated with VO2 changes independently of the hemodynamic intervention used. These results further underline the pathophysiological significance of V-A uncoupling in patients with hemodynamic instability.