Efficiency of different hollow-fiber hemofilters in continuous arteriovenous hemodiafiltration

Low dialysate to blood flow rate ratios are a unique characteristic of cont inuous arteriovenous hemodiafiltration (CAVHDF) that should allow complete saturation of dialysis fluid with small-molecular-weight blood solutes. The aim of the investigation was to evaluate the performance of different hemo filters in CAVHDF. In 10 critically ill patients with acute renal failure, the efficiency of four hollow-fiber hemofilters, polyamide 0.6 m(2), polyac rylonitrile (PAN) 0.3 and 0.6 m(2), acrylonitrile sodium methallylsulfonate (AN69HF) 0.6 m(2), has been evaluated. For comparison, dialysate flow rate s (Q(di)) were standardized to 16.6 and 25 ml/min. Samples for urea nitroge n were obtained from the arterial blood line (C-bi) and from the dialysate exit port (C-do) within 24-hour running time. Outflowing dialysate (Q(do)) was also measured at the same time. Blood flow (Q(b)) was calculated by the bubble transit time technique. Diffusive and total urea clearances were de termined. AN69HF and PAN hemofilters provided higher clearances than the po lyamide hemofilter. Despite the smaller surface area, PAN 0.3 m(2) had a to tal urea clearance comparable to that of PAN 0.6 m(2) and AN69HF at Q(di) = 16.6 ml/min. While at Q(di) = 16.6 ml/min equilibrium between blood and di alysate (C-do/C-bi congruent to 1) occurred with the AN69HF and PAN hemofil ters, at Q(di) = 25 ml/min the equilibrium was obtained only with the AN69H F hemofilter. In conclusion, almost complete urea saturation of dialysis fl uid has not been obtained with all hemofilters tested here. In our experien ce, membrane characteristics play an important role in determining diffusiv e efficiency in CAVHDF. Copyright (C) 2000 S. Karger AG, Basel.