Asymmetric polyamide hollow-fiber filters in the hemofiltration system.

We tested the asymmetric polyamide hollow fiber as the filter in the hemofiltration unit. Effective membrane thickness was 1mu, the diameter of the hollow fiber was 600mu, and the total surface was 1 m2. Membrane cutoff was determined at 13,000 daltons molecular weight. A fully automated system was used to replace the volume of ultrafiltrate with a balanced electrolyte solution. Clearance rates for BUN, creatinine, uric acid, and inorganic phosphate were calculated at 70-75 ml/min when prediluting (i.e., when balanced electrolyte solution is admitted to the arterial line of the extracorporeal circuit). Clearance rate for inulin was determined at 23 ml/min. Sieving coefficients for small molecular weight solutes were determined at 1.0 and for inulin 0.4. This decrease is explained by the development of a secondary protein layer and by unflavorable streaming conditions inside the hollow fiber. The ultrafiltrate remained free of protein.