Background: Cross-sectional studies showed that fluid overload (FO) measured by bioimpedance spectroscopy (BIS) predicted adverse outcomes in patients on peritoneal dialysis (PD). We aimed to describe the longitudinal change in volume status in Chinese PD patients and determine its relation with clinical outcomes.
Methods: We performed a single-centre, retrospective analysis of all PD patients who underwent repeated BIS from 2010 to 2015. FO was defined by relative hydration index (RHI; volume of overhydration adjusted by extracellular water >7%). Variability of volume status (VVS) was denoted by the standard deviation of all RHI. The association of time-averaged RHI and VVS on patient and technique survival was explored by a competing risk model.
Results: A total of 269 patients were followed for a median of 47.1 months. Mean time-averaged RHI was 17.6 ± 10.2%. Multivariable mixed linear regression revealed that RHI was significantly associated with diabetes, time-varying systolic blood pressure, and inversely with time-varying albumin level, lean tissue index and fat tissue index (p <0.0001 for all). Time-averaged RHI independently predicted patient survival (subdistribution hazard ratio (SHR) 1.05, 95% CI 1.03-1.07, p <0.0001) and technique survival (SHR 1.04, 95% CI 1.02-1.06, p <0.0001), whereas VVS did not. The mortality risk for patients with persistent FO was consistently higher than the corresponding risk estimated from baseline FO of the same extent.
Conclusions: Persistent FO was a strong predictor of patient and technique failure. Repeated bioimpedance measurements to monitor volume status may provide additional prognostic information in PD patients.
Keywords: Bioimpedance; fluid overload; mortality; peritoneal dialysis; variability of volume status.