A prospective randomised European multicentre study of medium-long run mortality and morbidity comparing acetate-free biofiltration and bicarbonate dialysis.

In recent years, the progressive increase in the mean age of the population entering chronic dialysis treatment has been responsible, on the one hand, for the growing number of patients undergoing regular dialysis, and on the other, for the high number of "critical" patients, both as a result of their age and the presence of concomitant morbidity. Thus, dialysis treatment today is not only aimed at waste removal and water-electrolyte homeostasis, but also at a reduction in morbidity and mortality, and at improving the patients' quality of life, thanks to the use of biocompatible materials and the achievement of good cardiovascular tolerance to treatment. Consequently, diffusive-convective dialysis procedures have been on the increase, since they combine better depuration with the use of biocompatible high-flux membranes. Acetate-free biofiltration (AFB) is a diffusive-convective dialysis procedure which utilises a high-flux membrane, AN69, post-dilution infusion of a sodium bicarbonate solution (NaHCO3), and a dialysate which is completely free of any buffer, and thus also free of acetate, which may have various negative effects on the patient. A number of studies have already shown the better hemodynamic stability and the reduction of intradialytic side-effects during AFB. All these, however, were short-term studies. To verify the beneficial effects of AFB in the long run, a three year multicentre randomised European trial has been proposed to compare bicarbonate hemodialysis (BD), a technique used in nearly 80% of the world's dialysis population, and AFB. The specific aim of the investigation is to verify, in a large number of patients, the results of hemodialysis treatment in terms of morbidity, mortality and quality of life. The study involves 80 hemodialysis units across Italy, France, Germany, Spain, Slovenia and Croatia, with enrollment of about 400 patients considered "critical" for at least one of the following reasons: age, diabetes, dialysis cardiovascular instability. Fifty percent of the patients are to undergo AFB with the AN69 membrane and bicarbonate solution infusion (NaHCO3 145 or 167 mEq/lt), and the other fifty percent are to be treated by BD, with any membrane except the nonmodified cellulosic one. Biochemical, cardiological, and nutritional parameters will be considered throughout the study. Mortality, morbidity both in terms of intra- and interdialysis symptoms - and hospitalisation rate, as well as the patients' quality of life, evaluated by the SF36 questionnaire, will be analysed.

Clinical status and acid-base balance during biofiltration in patients with acetate dialysis intolerance.

Nine patients intolerant to acetate hemodialysis were treated with biofiltration. This consisted in a 4-h acetate hemodialysis during which an additional 2 liters of ultrafiltrate were replaced by a bicarbonate solution (100 mEq/l). Hypotensive episodes disappeared and six out of nine patients were symptom-free during the session. Compared to standard hemodialysis, arterial blood bicarbonate and pO2 did not drop during biofiltration. The anion gap did not change during standard hemodialysis, but was significantly reduced during biofiltration (24.5 +/- 2.9 vs 19.9 +/- 1.4 mEq/l). In our conditions clinical results were positive with biofiltration. On the basis of anion gap changes and preliminary results of plasma acetate determinations, it is suggested that a better cellular metabolism of acetate may be induced by bicarbonate infusion.