Implications of different fluid overload definitions in pediatric stem cell transplant patients requiring continuous renal replacement therapy

Abstract

In critically ill pediatric patients, fluid overload (FO) >10% has been identified as a threshold for possible interventions, including initiation of continuous renal replacement therapy (CRRT). However, multiple definitions have been reported, and there remains no consensus method for FO calculation. The goal of this study was to compare different methods of FO determination and to assess their relative value in predicting outcomes. This is a retrospective single-center review of 21 pediatric stem cell transplant patients (PSCT) that required CRRT from 2004 to 2009. We compared eight definitions (4 weight-based and 4 fluid-balance based) that varied by baseline weights. Outcome measures were pediatric intensive care unit (PICU) mortality and pediatric logistic organ dysfunction (PELOD) scores. The number of patients identified as having >10% FO varied significantly according to the definition used, from 14 to 48% (p = 0.002). Significant intra-subject variability was observed; the median difference between individual minimum and maximum %FO scores was 11.4% (IQR 6.8, 17.1%). %FO was not significantly associated with PICU mortality, but five of eight FO definitions were predictive of higher subsequent PELOD scores. Our study is one of the first to compare different FO definitions and the impact on predicting outcomes. Our findings suggest that depending on the FO definition used, there is significant variability in the calculated %FO in PSCT patients, and this has important implications for clinical decision-making. Further studies are necessary to determine an optimal FO definition that is clinically relevant and predictive of important outcomes.