Sodium removal and plasma tonicity balance are not different in hemodialysis and hemodiafiltration using high-flux membranes.

Background: The clinical benefits of on-line hemodiafiltration (HDF) versus high-flux membranes hemodialysis (hf-HD) are still debated. In fact, although a superiority of one treatment over the other, especially in terms of mortality, did not emerge from the analysis of clinical trials, improved intradialytic vascular stability and cardiovascular mortality have been observed in patients undergoing HDF rather than hf-HD; the lower removal of sodium (Na) during HDF seems to play a major role. The plasma concentration of Na is the major determinant of plasma tonicity, which, by determining the flow of water between the intracellular and the extracellular compartment, contributes to the vascular refilling process and the maintenance of blood pressure during the hemodialysis treatment.