Elimination of beta 2-microglobulin by a new polyacrylonitrile membrane dialyser: mechanism and physiokinetics.

The performance and mechanism of beta 2-microglobulin (beta 2 M) removal by a new polyacrylonitrile membrane dialyser (CX2), and the physiokinetics of beta 2 M during treatment were studied. In vitro experiments showed that mean pore size of the CX2 membrane was 120 A, and the molecular cut-off point was less than 66,000 daltons. The diffusive capacity of the PAN 12CX2 dialyser (1.2 m2) for beta 2 M was calculated to be 27.3 ml/min at a blood flow of 200 ml/min, and it was considered that, compared to the elimination by local filtration induced by back-filtration and adsorption, diffusion was the major eliminating mechanism for beta 2 M. Although the elimination of beta 2 M increased linearly by augumentation of the ultrafiltration volume, diffusion was a major contributing factor for beta 2 M removal even in haemodiafiltration. Serum beta 2 M decreased to 51% and 44% of initial values after correction of haemoconcentration by a clinical haemodialysis or haemodiafiltration even under relatively low blood and filtrate flow conditions, and sieving coefficient and clearance of CX2 for beta 2 M compared well with in vitro results. The one-pool model simulation demonstrated that from 50 to 60 mg of beta 2 M was transferred from the intra- to the extracellular space during treatment. These results indicate that CX2 effectively eliminates beta 2 M mainly by diffusion, and that beta 2 M transfer to the plasma space during haemodialysis and haemodiafiltration may be accelerated.