Changes in Total Protein Concentration Due to Fluid Removal During and Shortly after Hemodialysis

Abstract

Background: Changes in plasma volume during hemodialysis are complex and have been shown to depend on the rate of fluid removal and the degree of fluid overload. We examined changes in total protein concentration during and shortly after a dialysis treatment in archived data from the HEMO study. Methods: During follow-up months 4 and 36 of the HEMO study, additional blood samples were obtained during a typical dialysis session at 30 and 60 min after dialysis. In 315 studies from 282 patients where complete data were available, we calculated the concentration change in total protein and compared it to the modeled change in both total body water and extracellular fluid space as derived from 2-pool urea kinetic modeling. Results: The mean postdialysis modeled urea volume (V) was 31.1 ± 6.18 L. Mean fluid removal was 2.76 ± 1.27 kg, over a session length of 207 ± 28 min. The ratio of predialysis V to postdialysis V averaged 1.090 ± 0.040. The mean TP ratios (post/pre) at 0, 30, and 60 min postdialysis averaged 1.121 ± 0.070 (SD), 1.091 ± 0.090, and 1.091 ± 0.086. The dialysate to serum sodium gradient, studied in a different group of treatments where this information was available, had no impact on these findings, nor did the length of the interdialytic interval. Conclusions: On average, after equilibration, the change in plasma volume due to fluid removal is similar to the modeled change in total body water (urea space), irrespective of dialysate to serum sodium gradient. This supports previous observations that during dialysis with ultrafiltration, plasma volume contracts to a lesser degree than the interstitial volume and that some fluid may be removed from spaces other than the extracellular fluid.

An extended kinetic model-based correction factor equation to account hemodialysis post-treatment hemoconcentration

“…During the hemodialysis procedure, the overhydration status of renal patients is controlled by a forced filtration of plasma water which leads to a concomitant increase of the concentration on some blood components, the so called hemoconcentration. 1 This effect may conduct to a misleading interpretation of post-treatment concentration levels of several solutes and moieties which are characterized by a particular distribution among body tissues. Up to now there are only two main strategies to account the hemoconcentration effect, relating intra-dialysis plasma changes to solute kinetics.…”