Study Evaluating the Effect of Isonatremic Dialysis Treatment in Chronic Kidney Disease Patients on Dialysis

Aim of this study is to evaluate, in a population of chronic kidney disease patients on dialysis (Stage 5D), the effect of treatment with isonatremic dialysis (vs conventional dialysis), during an observational period of 2 months each, on: * control of interdialytic weight gain * perdialytic tolerance in terms of adverse events occurring during all of the sessions of the study * body composition and thirst measured monthly during the 4 months of follow-up. * tolerance to treatment.