Beta 2-microglobulin kinetics during haemofiltration.

To study the kinetics of beta 2-microglobulin during haemofiltration, seven patients with end-stage renal failure were treated with the AN 69 (acrylonitrile), Duo-Flux (cellulose acetate) and F 60 (polysulphone) haemofilter. Low beta 2-microglobulin sieving coefficients and a highly negative filter mass balance error were observed during the initial phase of treatment with AN 69 but not with Duo-Flux or F 60, indicating a high degree of beta 2-microglobulin adsorption by AN 69. Total removal of beta 2-microglobulin was calculated by addition of the total amount adsorbed by the membrane and the total amount recovered in the collected ultrafiltrate. With AN 69 and F 60, total removal of beta 2-microglobulin amounted to 393 +/- 135 (SD) and 316 +/- 35 mg per treatment, while total removal with Duo-Flux was 242 +/- 79 mg per treatment. Thus, highly permeable membranes such as AN 69 or F 60 used in a haemofiltration mode may nearly balance the presumed generation of beta 2-microglobulin in uraemic patients. During treatment, an increase of the calculated beta 2-microglobulin distribution volume occurred with all three membranes, probably representing extra-to-intracellular water shifts. The water shifts occurring during haemofiltration reduce the value of precision of beta 2-microglobulin kinetics and limit the value of the plasma level decrease as an index of beta 2-microglobulin removal.