The use of dialysate sodium that is markedly lower compared with the patient’s serum sodium results in rapid reduction in the plasma osmolality and intravascular volume, leading to disequilibrium symptoms and hypotension, however, when used at smaller gradients, sodium will not flux into the patient and, post dialysis thirst is prevented without undesireable hemodynamic events. Dialysate sodium higher than serum sodium may help to maintain blood pressure with ultrafiltration, but leads to post-dialytic thirst, fluid induced weigh gain and hypertension. Creating a positive intradialytic sodium balance is effective in acutely reducing the incidence of intradialytic symptoms, but it also sustains a vicious cycle hampering the attainment of dry weight and pre disposes the patient to an increased risk of intra dialytic complications during the following dialysis session. An isonatric hemodialysis may have a beneficial effect on blood pressure and dialysis tolerance. A biofeedback system using hemodialysis filtrations regeneration of ultrafiltrate has been specially developed with an isonatric mode maintaining an equal serum sodium concentration between the start and the end of the dialysis session, combined with ultrafiltration and conductivity profiles.