[Advantage of a high-sodium hemodialysis solution: theoretical bases].

In hemodialysis, an excessive oversimplification leads to confuse the transfer direction of a given solute (patient towards dialysate or dialysate towards patient) and the direction of transmembranar concentration gradient. Applied to sodium, this confusion leads to the usual iso- or hypotonic dialysate use, in order to eliminate the patient's sodium overload. We show here how the use of a high sodium dialysate allows the elimination of the sodium overload and makes the free water clearance (approached by the Na-free water clearance) positive, which is the necessary condition to restore an hydro-electrolytic equilibrium near from the normal. That allows a disappearance of hypovolemic symptoms during hemodialysis, a better general condition and a possible increase of water intake between sessions.