The effects of zero-balance ultrafiltration on postoperative recovery after cardiopulmonary bypass: a meta-analysis of randomized controlled trials

Objective: Considered as a significant ultrafiltration technology during cardiopulmonary bypass (CPB), zero-balance ultrafiltration (Z-BUF) has always received controversial support regarding its effectiveness in reducing inflammatory mediators in plasma. Therefore, we conducted a meta-analysis to evaluate the clinical effect of Z-BUF through screening all relevant published randomized controlled trials (RCTs). Methods: A comprehensive search was conducted to screen all RCTs of Z-BUF. Three trained investigators searched databases, including PubMed, Embase, the Cochrane Library, Google scholar, and Chinese literature databases (CNKI, WanFang, WeiPu). RCTs that compared Z-BUF with non-ultrafiltration were included. We focused on clinical outcomes such as length of stay in ICU, duration of ventilation, hospital stay, total amount of chest tube drainage and mortality. Finally, a total of 7 studies containing appropriate criteria were divided into an adult group and a pediatric group. A random effects model was used to calculate weighted mean difference with 95% confidence intervals. Results: In the adult group, the benefits of Z-BUF in duration of ventilation (WMD=-2.77, 95% CI = [-6.26, 0.72], I2=71%, p=0.12) and the length of ICU stay (WMD=-4.13, 95% CI = [-10.09, 1.84], I2=77%, Z=1.36, p=0.17) were not apparent, with significant heterogeneity existing in the statistical results. The rest of the clinical parameters could not be evaluated due to insufficient data. In the pediatric group, combined analysis showed Z-BUF could reduce the duration of mechanical ventilation (WMD=3.07; 95%CI= [-7.56, -3.46], I2=17%, p=0.27). The advantage of Z-BUF was not observed in other clinical outcomes. Conclusion: The benefits of Z-BUF were not apparent, according to the report. Further studies involving combined ultrafiltration are expected to provide improved ultrafiltration during CPB.