Intra and extra cellular fluid shifts during the inter dialytic period in conventional and daily hemodialysis patients.

Previous studies indicate that fluid loss during dialysis occurs from the leg extracellular fluid (ECF) maintaining the central blood volume (CBV). Our goal was to determine change in ECF and intracellular fluid (ICF) volumes for the segments of the body throughout the inter-dialytic period. Six conventional and five daily subjects on hemodialysis (HD) had segmental bioimpedance (SBIA) performed using the Hydra ECF/ICF Spectrum Analyzer 4200. Measurements were taken pre/postdialysis and 1, 2, 4, and 24 hours after dialysis. The conventional dialysis patients had measurements 48 hours after dialysis. There were no differences in baseline characteristics noted between the conventional and daily HD patients. For both groups, from pre to postdialysis, there was a reduction in the ECF for each of the segments (leg, arm, and trunk) (p < 0.05). There was no change in ECF during the 4 hours after dialysis. ECF values at 24 hours for both groups returned closer to baseline. The conventional group's leg and arm ECF returned to baseline at 48 hours. This suggests that ECF is slowly refilled during the inter-dialytic period. The majority of fluid loss and refilling takes place in the extremities to maintaining the CBV. The increase in leg ECF mimics the consumption of fluid during the inter-dialytic period.