Why does the choice of dialysate sodium concentration remain controversial?

The choice of the ideal dialysate sodium concentration remains controversial. Most dialysis centers have a standard dialysate concentration. In theory, choosing a dialysate sodium concentration lower than serum sodium should result in an additional loss of sodium by diffusion with a reduction in the prevalence of hypertension and interdialytic weight gains (IDWGs) on one hand, but with potential increased risk of intradialytic hypotension and cramps on the other hand, and the opposite effects may accompany the choice of dialysate sodium concentrations greater than serum concentration. Although most studies have reported a reduction in IDWG with lower dialysate sodium concentrations, the effects on blood pressure control, and adverse intradialytic events have been variable. Different outcomes between studies may be partially explained by patient selection, with differences in dietary sodium intake, urinary sodium losses, and sodium stores in the body. In addition, multicenter trials potentially introduce additional confounders, including differences in local quality control of delivered dialysate sodium concentration and sodium measurements. Although there may be advantages for lower dialysate sodium concentration, observational studies have reported a survival advantage for higher dialysate sodium concentrations for those patients with lower serum sodium concentrations pre-dialysis. As there is no current consensus for a universal dialysate sodium concentration, attention has turned to considering an individualized approach to choosing a dialysate sodium concentration.