On-line hemodiafiltration:: Comparison of eleven different high-flux dialyzers

At present we have a great variety of high-flux dialyzers whose characteristics in vitro seem similar. On-line HDF is a technique which combines diffusion with elevated convection and uses dialysate as replacement fluid. On-line HDF provides the highest clearances for small, medium-sized and large molecules and gives the best performance from the dialyzers. Conscious of this wide choice of dialyzers we evaluated the performance of different dialyzers in renewing small and medium-large molecules. Eleven patients were included in this study 7 males and 4 females. Every patient received II on-line HDF sessions with Fresenius 4008B machine, Qi 100 ml/min or 6 Vh, QB 400 ml/min, QB 800 ml/min, UF 0.5 L/h and Td GO min. only the dialyzer was changed: 1.9 m(2) cellulose triacetate (Tricea 190G), 2.1 m(2) poly methyl methacrylate of PMMA (BK-2. 1P), 1.8 m(2) polyester-polymer Allol or PEPA (FLX-18GWS), 2,05 m(2) acrylonitrile (Filtral 20), 2.7 m(2) polyamide (Poliflux 2.1) and 1.8-2.4 m(2) polysulfones (HF 80, BS-1.85, APS-900, Arylane H9, Idemsa 2000, HdF 100). Arterial pressure, venous pressure and transmembrane pressure (TMP) were monitored. Plasma, urea, creatinine, phosphate, uric acid and beta(2)m concentrations were measured at the beginning and at the end dialysis from arterial and venous blood lines, and arterial blood line with the slow flow method. Recirculation, dialyzer solutes clearance and solute reduction rates were calculated. No significant differences were found in arterial pressure, venous pressure and recirculation. Small molecule removal was similar except in BK-2. 1P and HdF 100 dialyzers which were lower and higher respectively. There were differences in TMP and beta(2)m removal among dialyzers employed. Mean TMP, beta(2)m clearance and beta(2)m reduction ratio were: Tricea 190G (TMP 336 mmNg, beta(2)m K 79 ml/min and beta(2)m reduction ratio 44.9%), BK-2.1p (TMP 485, beta(2)m K 102 and beta(2)mRR 48.3%), FLX-18 GWS (TMP 195, beta(2)m K 140 and beta(2)mRR 54.6%), Filtral 20 (TMP 245, beta(2)m K 132 and beta(2)mRR 54.1%), Poliflux 2.1 (TMP 209, beta(2)m, K 158 and beta(2)mRR 56.0%), HF 80 (TMP 208, beta(2)mRR k 160 and beta(2)mRR 57.4%), BS-1.8S (TMP 186, beta(2)m K 179 and beta(2)mRR 59.6%), APS-900 (TMP 174, beta(2)m 176 and beta(2)mRR 64.8%), Arylane H9 (TMP 206, beta(2)m, K 171 and beta(2)mRR 59.9%), Idemsa 2000 (TMP 203, beta(2)m K 169 and beta(2)mRR 60.4%), HdF 700 (TMP 752, beta(2)m K rse and beta(2)mRR 64.6%).