Beta 2-microglobulin kinetics during haemodialysis and haemofiltration.

Since the identification of beta 2-microglobulin as a major component of 'dialysis amyloid', concern about its removal by different dialysis methods has been raised. Haemodialysis with regenerated cellulose membranes increases serum beta 2-microglobulin by 10-15%. Serial measurements show a very early increase during cuprophan haemodialysis, the mechanism of which is as yet unknown. After cuprophan haemodialysis, serum values return to the initial pretreatment concentrations by the time of the next haemodialysis. In contrast to regenerated cellulose, dialysis with polycarbonate lowers serum beta 2-microglobulin by 8%, and dialysis with polysulphone by 53%. As opposed to cuprophan, after polysulphone haemodialysis the serum concentrations have not returned to the initial pretreatment levels within 48 h. Comparison of beta 2-microglobulin removal using the same polysulphone membrane for haemodialysis and haemofiltration shows that beta 2-microglobulin is more effectively removed by convection than by diffusion when both treatment modes are matched for blood flow and urea clearance. Therefore, in contrast to haemodialysis with regenerated cellulose membranes, where a transient, intradialytic release of beta 2-microglobulin is induced, significant removal is observed using higher permeable membranes. These findings may have implications for the generation of 'dialysis amyloid'.

High-flux synthetic versus cellulosic membranes for beta 2-microglobulin removal during hemodialysis, hemodiafiltration and hemofiltration.

Efficient removal of beta 2 microglobulin (beta 2-M) in end-stage renal failure patients is a continuing preoccupation, as the incidence and severity of dialysis-associated amyloidosis are increasing. To evaluate comparative beta 2-M removal we studied six stable end-stage renal failure patients during high-flux 3-h haemodialysis, haemodia-filtration, and haemofiltration, using acrylonitrile, cellulose triacetate, polyamide and polysulphone capillary devices. The reduction of plasma beta 2-M, total removal in ultrafiltrate/dialysate, and beta 2-M sieving coefficients were measured by RIA. The results suggest that convection plays the major role in beta 2-M removal when high-flux synthetic membranes are used in combination with high blood flow rates. In contrast, using the cellulose triacetate membrane under investigation, beta 2-M removal is diminished when ultrafiltration rates are increased. Accordingly, in any future prospective study on the role of beta 2-M retention in the amyloidogenesis, it is recommended that high-flux synthetic membranes be employed rather than the type of high-flux cellulosic membranes used in this study. The modality with which these synthetic membranes are used is probably less important, as long as maximum convective transport rates are obtained. Under present conditions, this will imply haemofiltration or haemodiafiltration rather than haemodialysis.