Assessing the hydration status of children with chronic kidney disease and on dialysis: A comparison of techniques

Abstract

Background. Fluid balance is pivotal in the management of children with chronic kidney disease (CKD) and on dialysis. Although many techniques are available to assess fluid status, there are only a few studies for children, of which none have been comparable against cardiovascular outcome measures. Methods. We performed a longitudinal study in 30 children with CKD5-5D and 13 age-matched healthy controls (71 measurements) to determine a correlation between optimal weight by bioimpedance spectroscopy (Wt-BIS) and clinical assessment (Wt-CA). The accuracy ofWt-BIS [relative overhydration (Rel-OH)] was compared against indicators of fluid status and cardiovascularmeasures. Results. There was poor agreement between Wt-CA and Wt-BIS in children on dialysis (P0.01), but not in CKD5 or control subjects. We developed a modified chart to plot Rel-OH against systolic blood pressure (SBP) z-score for the appropriate representation of volume status and blood pressure (BP) in children. In total, 25% of measurements showed SBP>90th percentile but not with concurrent overhydration. Rel-OH correlated with peripheral pulse pressure (P0.03; R0.3), higher N-terminal pro-brain natriuretic peptide (P0.02; R0.33) and left ventricular end-diastolic diameter (P0.05; R0.38). Central aortic mean and pulse pressure significantly associated with the left ventricular end-diastolic diameter (P0.03; R0.47 and P0.01; R0.50, respectively), but not with Rel-OH. SBP was positively associated with pulse wave velocity z-score (P0.04). In total, 40% of children on haemodialysis and 30% on peritoneal dialysis had increased left ventricularmass index. Conclusions. BIS provides an objective method for the assessment of hydration status in children on dialysis. We noted a marked discrepancy between BP and hydration status in children on dialysis that warrants further investigation.