ACETATE-FREE BIOFILTRATION (AFB) - A COOP ERATIVE STUDY IN 61 PATIENTS

AFB is a hemodiafiltration (HDF) technique without buffer in the aceta te-free dialysate, and with HCO3Na 1/6 M infusion in postdilution mode , using an AN69 filter. A retrospective and multicenter study was done in 61 patients with chronic renal failure on hemodialysis (HD), with more than three months follow-up on AFB.Before patients started on AFB , the mean time on dialysis was, 67 +/- 55 months, and previous dialys is techniques were: HDF in 33.5 % of patients, bicarbonate HD in 23.5 %, acetate HD in 36.5 % and hemofiltration (HF) in 6.5 %. Membranes pr oviously used were highly permeable membranes in 37 % and cuprophan in 63 %. Initially AFB technique was uniform in 49 patients, three times /week, 3hr/session, blood flow rate maintained about 350 ml/min, reinf usion rate of 2 l/hr postdilution of bicarbonate 1/6 M, polyacrylonitr ile hollow fiber hemodiafilter 1.3 sq.m. (F12), dialysis unit Monitral BSM2. Dialyzer was changed to polyacrylonitrile hollow fiber hemodiaf ilter 1.7 sq.m. (F16) and reinfusion 2.3 ml/h in 19 out of 49 patients . In 31 other patients the second AFB technique (AN69 1.7 s.q.) was us ed from the beginning. In the first group the follow-up was more than 12 months in all patients, mean time 14.6 months, in the last group th e mean follow-up was 8.8 months. Blood pressure, interdialytic wight g ain, incidence of hypotension and other symptoms of intolerance, phosp athe-calcium, lipid and nutritional metabolism parameters, acid-base s tatus, TAC, PCR, Kt/V and B2m were obtained and recorded at before and 1 and 12 months and when the study was finished. Session time was red uced in AFB technique with F12, from 204 to 184 min., without changes in the plasma concentrations of small molecules and maintained Kt/V, 1 .09-1.12. Serum B2m was significantly reduced (45 vs 39 mg/l, p <0.05) and predialytic bicarbonate increased significantly in AFB (p < 0.01) , from 19.5 to 21.3 mEq/l. PCR increased from 0.96 to 1.16 p/kg/d, alt hough without any change in other nutritional parameters. Serum calciu m, phosphate and PTH did not change during the study, but the increase in oral calcium salts ingested may be due to a negative Ca balance in AFB. Session time was also reduced in AFB technique with F16, from 20 4 to 189 min., without changes in levels of small molecules and mainta ined Kt/V (1.11-1.11). B2m was significantly reduced (50 vs 35 ng/l, p < 0.01) and predialytic bicarbonate increased significantly in AFB (p < 0,01), from 19.2 to 21.8 mEq/l. PCR increased from 1 to 1.19 g/kg/d , although without any change in other nutritional parameters. The inc idence of hypotension, headache muscle cramps and nausea was lower in patients on AFB (F12-16) than in other techniques. We conclude AFB is an adequate short dialysis technique which improves acidosis correctio n and increases the patient comfort and stability.