The prognostic value of volume status assessment by bioelectrical impedance analysis and lung ultrasound on mortality in septic acute kidney injury patients undergoing continuous renal replacement therapy

Abstract

Background

Septic acute kidney injury (AKI) is one of the most common causes in critically ill patients requiring continuous renal replacement therapy (CRRT). The fluid status of the patient is known as a significant risk factor for mortality in those patients. Therefore, it is necessary to find an objective assessment of volume status. The aim of present study is to elucidate the impact of fluid status assessed by bioelectrical impedance analysis (BIA) and lung ultrasound on clinical outcomes in septic AKI patients with CRRT.

Methods

Septic AKI patients requiring CRRT between April 2014 and February 2015 at Yonsei University Health System were included. Surrogates of volume status were defined by 1) percent of body weight change between CRRT initiation and admission day, 2) over-hydration (OH)/extracellular water (ECW) measured by BIA, and 3) B-lines measured by lung ultrasound (US). Prognostic values of surrogates of volume status for 28-day mortality were evaluated.

Results

Among the 36 enrolled patients, 19 (52.8%) patients died during the follow-up duration. The mean percentage of weight change and OH/ECW measured by BIA was 5.3±20.7 % and 0.3±0.1 L/L. The median number of B-lines counted by lung US was 6 (interquartile range 4-10). Kaplan-Meier analysis showed that the risk for 28-day mortality was higher in patients with the highest OH/ECW tertile compared to patients with lower OH/ECW values (log-rank test, P=0.020). Percent of weight change and the number of B-lines were not significantly related with 28-day mortality risk (log-rank test, P=0.443 and P=0.450 respectively). Multivariate Cox proportional hazard regression analysis showed that higher OH/ECW measured by BIA was an independent risk factor for 28-day mortality after adjustment of confounding factors (HR=3.83, 95% CI=1.04-14.03, P=0.043).

Conclusion

Higher OH/ECW measured by BIA was an independent risk factor for 28-day mortality in septic AKI patients undergoing CRRT. Determining fluid status by BIA could be a useful method to stratify mortality risk in this patient group.