We studied the adsorption of anaphylatoxins C3a and C5a on acrylonitrile (AN69) hollow-fiber (AN69HF) and plate (AN69P) dialyzers in 8 patients during 4-hour hemodialyses (HD). Blood passed first through a cuprophan dialyzer and then through AN69 dialyzers that were not in contact with dialysis fluid. Plasma C3a and C5a were measured in samples taken from the afferent and efferent blood lines of the acrylonitrile dialyzers at 15, 60 and 240 min. Plasma C3a concentrations decreased significantly in blood that had passed through AN69 dialyzers. This decrease, indicating membrane adsorption, was maximal (by 65% in AN69HF and by 59% in AN69P) at 15 min and minimal (by 53% in AN69HF and by 18% in AN69P) at 240 min. The decrease in plasma C5a concentrations was smaller and significant throughout HD only with AN69HF. The amount of C3a adsorbed was at least 45,000 micrograms in AN69HF and 18,000 micrograms in AN69P. These findings demonstrate that acrylonitrile dialyzers adsorb more C3a and C5a than they produce. This membrane adsorption may explain why the increase of plasma C3a and C5a is inhibited during HD.
To check whether in vivo EDTA prevents complement activation resulting from blood contact with the dialyzer membrane, sham hemodialysis (HD) was performed in seven healthy volunteers using Cuprophan hollow-fiber dialyzers. Blood samples were drawn from the arterial and venous blood lines of the dialyzer before and after EDTA was infused into the arterial line. Venous line plasma C3a concentrations before EDTA infusion were significantly higher than after EDTA. Also, venous line plasma C3a concentrations before and after EDTA infusion were significantly higher than in the arterial line. These results indicate that complement activation can be attenuated by EDTA during sham HD. Technical improvements in the procedure may permit complete inhibition of complement activation.
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