Cytokine production in haemodiafiltration: a multicentre study.

BACKGROUND Bacterial contamination of dialysate may enhance cytokine production in haemodialysis. We tested the hypothesis that intracellular cytokines could be enhanced in a large group of patients exposed to backfiltration of dialysate over a long period of observation. METHODS The intracellular cytokine (interleukin-1 receptor antagonist and interleukin-1beta) concentrations in chronic uraemic patients undergoing haemodiafiltration, which is known to be associated with backfiltration (Group II, 12 patients), were compared to those found in patients treated with a modified haemodiafiltration modality without backfiltration (Group I, 16 patients), in patients shifted from one modality to the other (Group III, 27 patients) and in 10 patients on haemodialysis (Group IV) in a 1-year multicentre study. Group V comprised 10 healthy volunteers. All dialysis monitors were equipped with dialysate ultrafiltration systems. Dialysate contamination was studied by the LAL and the peripheral mononuclear cell/interleukin-1beta assays in the presence or absence of polymyxin B. RESULTS Intracellular interleukin-1 receptor antagonist and interleukin-1beta both increased significantly (P < 0.002) but slowly (after 8 months) in Groups II vs I, and during the 4-month period in haemodiafiltration with backfiltration in Group III. The incidence of post/predialysis concentration ratio (over 1.5) increased two- to threefold in patients treated with haemodiafiltration with backfiltration with respect to haemodiafiltration without backfiltration. Results on the assays for LAL (< 0.5 E/ml) and interleukin-1beta (range 80.1-90.2 pg/5 x 10(6) cells; 70.2-81.3 pg/5 x 10(6) cells with polymyxin B) showed a moderate-to-low degree of dialysate contamination. CONCLUSIONS Backfiltration of dialysate with moderate-to-low degree of contamination may enhance cytokine synthesis in the long term. Thus, the relevance for dialytic strategies aiming at improving dialysate quality and/or at reducing backfiltration is highlighted.