Convective and adsorptive removal of beta2-microglobulin during predilutional and postdilutional hemofiltration.

BACKGROUND: Beta(2)-microglobulin (beta2-m) removal in patients with end-stage renal disease (ESRD) is maximal with convective techniques, such as hemofiltration (HF) or hemodiafiltration (HDF). Although the infusion mode of the replacement solution (predilution or postdilution) is expected to influence the efficiency of HF, experimental data in this respect are scanty. We therefore investigated the impact of the fluid reinfusion mode on the efficiency of HF in 11 ESRD patients who underwent both treatments. METHODS: The dialyzer (AK 200 ULTRA) was equipped with a 3-layer polyamide membrane (Poliflux 21 S, surface 2.1 m(2)) and blood flow was kept between 300 and 400 mL/min. beta2-m concentrations were measured in plasma water and ultrafiltrate at appropriate times during a 240-minute treatment. The following dialytic parameters were calculated: total amount of beta2-m removed (A(tot)), beta2-m removed by convection (A(con)) and by adsorption (A(ads)), percent reduction in beta2-m plasma water concentration (% Cpw(in)), total plasma water clearance (CLpw(tot)), convective plasma water clearance (CLpw(con)), adsorptive plasma water clearance (CLpw(ads)), and sieving coefficient (SC). RESULTS: CLpw(tot), CLpw(ads), and% Cpw(in) were similar in pre- and postdilutional conditions, whereas CLpw(con) and SC were higher and CLpw(ads) was lower in postdilution than in predilution HF. Since a significant inverse correlation was found between A(ads) and SC, predilution probably determines greater protein fouling than postdilution. CONCLUSION: The 2 techniques appear to be equivalent in terms of total beta2-m removal, although this final result is obtained by different contributions of convective and adsorptive elimination.