Calf Bioimpedance Analysis: A Novel Approach for Evaluating Hydration Status in Pediatric Dialysis Patients Under High Dialysate Sodium.

INTRODUCTION

Assessment  of  hydration  status  in  pediatric hemodialysis is complicated by dynamic fluid shifts and sodium variability.  Conventional  methods  such  as  clinical  evaluation and  whole-body  bioimpedance  analysis  (BIA)  lack  precision  for individual-level monitoring. This study introduces a calf impedance ratio (ΔZ₁₅ₖₕ / ΔZ₁₅₀ₖₕ) to classify fluid responses and evaluate the impact of high dialysate sodium (143 mEq/L) on fluid dynamics and blood pressure.

METHODS

A  cross-sectional  study  was  conducted  involving  14 children aged 5-12 years undergoing maintenance hemodialysis. Impedance was measured pre- and post-dialysis at two frequencies using  a  custom-built  device.  The  raw  impedance  changes  were analyzed  without  conversion  to  fluid  volumes,  allowing  for classification  into  three  physiological  response  groups  based  on the impedance ratio.

RESULTS

Three  distinct  physiological  profiles  emerged.  Group1  (ΔZΔZ150kh15kh > 1)  showed  effective  extracellular  fluid  removal  with stable  hemodynamics.  Group  2  (ratio  between  0  and  1)  reflected minimal  Extracellular  Water  (ECW)  ECW  changes,  potentially due  to  sodium-driven  redistribution,  with  additional  influence from  sodium-enhanced  tissue  conductivity.  Group  3  (ΔZ₁₅ₖₕ < 0) exhibited paradoxical impedance decreases despite fluid removal,along  with  sodium  increase  and  blood  pressure  elevation.  ΔZ₁₅ₖₕpositively correlated with ΔBP-sys (r = 0.650, P = .012).

CONCLUSION

The impedance ratio (ΔZΔZ150kh15kh ) provides a sensitive index for classifying fluid responses and identifying sodium-related effects in pediatric hemodialysis. It may support individualized dialysis prescriptions by guiding adjustments in ultrafiltration and dialysate sodium to improve hemodynamic stability and fluid balance.