On complement net generation in fast hemodialysis: are high blood flow rates bioincompatible?

Arterial and venous concentrations of complement (C3a) and leukocyte count were determined in 17 patients during 201 hemodialysis sessions by 12 different treatment modes executed in random order using cuprophan, hemophan, or polyamide membranes with small or large membrane areas and high blood flow (Qb) (400 mL/min) for 2 hours or low Qb (200 mL/min) for 4 hours. With all membrane types, the number of leukocytes was significantly higher after 120 minutes of dialysis and by the end of treatment at high Qb compared with low Qb. C3a concentrations (microgram/mL) in the arterial and venous blood lines were significantly higher during cuprophan dialysis compared with hemophan and polyamide dialyses (P < 0.001). In addition, the net generation of C3a (microgram/min) was significantly higher during hemodialysis with cuprophan compared with hemophan and polyamide (P < 0.001). After 2 hours at high Qb for each of the three membranes, the net generation of C3a was significantly higher compared with low Qb (P < 0.05 for all comparisons). Possible reasons for the increase in the net generation of C3a (microgram/min) at high Qb are less protein deposition on the membrane at high Qb or the fact that the protein coat is stripped off in the dialyzer, thereby recreating a less biocompatible surface. Hemodialysis at high Qb may thus be less biocompatible than dialysis at low Qb.