[Clinical dialysis: new problems and new prospects]

The main problem nephrologists have to face today is the very high patient morbidity and mortality. A number of traditional and non-traditional risk factors have a role; among these anaemia, hypertension, dislipidemia, abnormalities in calcium-phosphate metabolism, hyperhomocysteinemia and endothelial dysfunction. An important innovation in the field of hemodialysis has been the availability of high-permeable and high-flux membranes, characterized by a high biocompatibility and ultrafiltration coefficient. The development of automatic systems to control ultrafiltration has enabled the utilisation of these membranes in the clinical setting (high-flux hemodialysis, hemofiltration, hemodiafiltration). It is common opinion that high-flux membranes can positively influence cardiovascular instability, but this has not been confirmed by clinical trials. Although preliminary data indicated a favorable effect on the correction of anemia in patients treated with high-permeable membranes, randomized trials have not shown a significant effect. Better control of anemia could be possible by means of on-line treatments, given their higher removal of medium- and large molecules and reduced microbiological and pyrogenic contamination of the dialysate. A number of analyses showed a lower incidence of bone cysts and/or carpal tunnel syndrome in patients treated with high-flux membranes compared to low-flux ones. High-flux treatments could reduce morbidity and mortality in hemodialysis patients. However, despite its large sample size, the HEMO Study has not been capable of showing a statistically significant effect of higher dialysis dose and high-flux membranes on survival and morbidity. The MPO study has been expressively designed to do a prospective evaluation of the long-term effect of membrane permeability on clinical outcomes. These results are greatly awaited.