Evaluation of bidirectional aluminum transfer across hollow fiber dialyzers

The ultrafiltrable fraction of plasma aluminum (UFAl) determined utilizing the hollow fiber dialyzer is variable and ranges from 10% to 50%. This extreme variability in UFAl led us to examine the possibility of Al binding to the hollow fiber dialyzer. Ultrafiltrate of aqueous Al solutions was obtained by applying a negative pressure of 250 mm Hg to a hollow fiber dialyzer (TriEx-1). In the first of three experimental protocols, Al was measured before and after recirculation of solutions containing 344 to 9244 micrograms/L Al through a hollow fiber dialyzer until the entire volume was collected as ultrafiltrate. UFAl ranged from 0.9% to 37.6% and did not correlate with the initial Al concentration. Total Al binding ranged from 42 micrograms to 1.3 mg. In the second, 16 L of aqueous AlCl3 solution (n = 3), containing from 205 to 411 micrograms/L Al were passed through the blood compartment of a hollow fiber dialyzer. The percentage of UFAl ranged from 4.1% to 17.3% during the first 20 minutes and 79.3% to 81.8% at 120 minutes. Finally, to investigate Al transfer from dialysate, 16 L of deionized distilled water were passed through the blood compartment while 16 L of AlCl3 solutions of 330 micrograms/L and 398 micrograms/L AI passed through the dialysate compartment. Samples were collected from blood and dialysate outflow ports every 20 minutes for 120 minutes. The transfer of Al from dialysate to blood compartment increased with time. However the concentration of Al at the blood outflow port never reached that at the dialysate outflow port.(ABSTRACT TRUNCATED AT 250 WORDS)