[Aspects of the on-line hemodiafiltration with regeneration and reinfusion of the ultrafiltrate (HFR): multicenter study].

: Despite technological advances in dialysis treatment, survival, morbidity and the quality of life in hemodialysis (HD) patients are affected by long-term complications, often related to the treatment itself. Among these complications, moderate protein and caloric malnutrition are present in approximately 30% of dialysis patients and are viewed as major contributors to increased mortality. In malnutrition pathogenesis, great importance is given to protein catabolism and to the loss of somatic protein and amino acids during dialysis. On the contrary, toxin clearance is believed to influence, positively, both protein anabolism and dietary protein intake. In hemodiafiltration (HDF), the clearance process is potentiated by three mechanisms (diffusion, convection and adsorption) and this could have a favorable effect on malnutrition. In addition, the reinfusion of regenerated ultrafiltrate (UF) would avoid the loss of large amounts of useful solutes as occurs with standard HD. In fact, all amino acids are present in the UF, which is not important in standard HD, but could be a problem in hemodiafiltration reinfusion (HFR). We treated 16 patients with HFR during the previous 3 months (the study will last for 12 months). Patients had been previously treated with bicarbonate dialysis for at least 6 months. The clinical tolerance of HFR was excellent and the technique appeared to be quite simple. The preliminary biochemical results demonstrated the stabilization of some parameters (such as urea and uric acid) with an adequate clearance of small molecules, while variables related to nutritional status (body weight, serum albumin and serum transferrin) did not change substantially. Surprisingly, the loss of both branched chain amino acids (BCAA) and essential amino acids (EAA) seemed slightly lower in HFR compared with standard HD. However, the reduced loss of amino acids (AA) observed with HFR should take into account other factors, such as absorption on adsorbent material and the basal plasma AA concentrations. Therefore, although each patient is in control of himself, it is difficult to draw any definite conclusions after only 3 months. However, it is evident that the loss of AA in HFR is quite modest and is not increased by the fact that it is a hemofiltration technique with all the consequent positive effects.