Acetate-free biofiltration: hemodiafiltration with base-free dialysate.

Bicarbonate dialysis has several clinical advantages compared to conventional acetate hemodialysis. However, the use of bicarbonate in the dialysate requires complicated hardware with considerable maintenance and servicing. We have developed a new dialysis technique, a modification of hemodiafiltration, called acetate-free biofiltration (AFBF), with no base replacement agents in the dialysate and with the infusion of bicarbonate solution in postdilution fluid. This study consisted of two parts, an acute phase (8 dialysis patients) and a chronic phase (4 patients) lasting up to 12 months. In the first phase we evaluated the effects of different amounts of infused bicarbonate (from 751 to 1,002 mEq per session) on acid-base balance. The best correction of uremic acidosis was obtained with the infusion of 900-1,000 HCO3 mEq during a 3-hour AFBF. There was a significant (p less than 0.0001) positive correlation between infused and gained bicarbonate. In the chronic part, 880-910 HCO3 mEq was infused per session and there was an increase in mean pretreatment plasma bicarbonate from 18.1 +/- 2.2 upon starting to 22.8 +/- 0.4 mEq/l by the end of the 12-month period. A very low incidence of intradialytic hypotension and stable serum chemistries were achieved with this technique as compared with standard hemodialysis despite a reduction of 3 h in weekly treatment time. AFBF is an easy-to-use, safe alternative to bicarbonate dialysis thanks to the absence of pyrogen reactions and comparatively low-cost maintenance.