Effects of urinary output at 2 hours after an initiation of continuous renal replacement therapy on mortality in septic patients with acute kidney injury

Objective Based on a secondary analysis of a retrospective cohort study, our study aimed to investigate the effects of urine output at 2-hours after initiation of continuous renal replacement therapy(CRRT)on the mortality at 28 and 90 days in sepsis patients with acute kidney injury(SAAKI). Methods This study was conducted using a retrospective cohort design, with secondary use of electronic medical records data which retrospectively collected SA-AKI patients undergoing CRRT in the ICU of Health System Severance Hospital and Ilsan Hospital in Korea from January 2009 to September 2016. Kaplan-Meier(K-M)curve, log-rank test, proportional hazard regression model(Cox)and trend test were performed to analyze the independent effects of UO2 h on mortality at 28 and 90 days. Also, stratified analysis and interaction test were conducted for subgroup analysis. Finally, we examined the possible nonlinear threshold effects of UO2 h on mortality by smooth curve fitting, piecewise linear model, recursive method et al. Results A total of 789 SA-AKI patients was included in our study. K-M curve and log-rank test found the mortality rate in patients with high UO2 h was significantly lower than that in patients with low UO2 h on 28 and 90 days. Adjusted Ⅱ Cox model revealed UO2 h was independently negatively associated with mortality at 28 and 90 days(mortality risk at 28 days:HR=0.84, 95% CI:0.75~0.94, P=0.003; mortality risk at 90 days:HR=0.88, 95% CI:0.79~0.97, P=0.009). In addition, there was a significant linear trend correlation between the two(P for trend <0.05). The stratification and interaction test indicated that serum albumin and UO2 h had a significant interaction effect on mortality at 90 days. The threshold effect analysis demonstrated that the nonlinear correlation between UO2 h and mortality was not significant and no threshold effect exist between them. Conclusions UO2 h was independently negatively correlated with mortality at 28 and 90 days in SA-AKI patients undergoing CRRT. No evidence of a non-linear relationship between them was detected.