Background: The influence of a dialysis session using hemodiafiltration with on-line regeneration of the ultrafiltrate (HFR) is compared with that of a conventional hemodialysis session with polysulfone (HD-PS) and with a group of healthy individuals. Methods: Total antioxidant capacity (TAC), antioxidants, i.e., superoxide dismutase (SOD) glutathione peroxidase (GPX), reduced glutathione (GSH) and catalase, and biomarkers of oxidative stress were evaluated in plasma, whole blood and lymphocytes. Results: The study showed decreased plasma TAC, decreased activities of antioxidant enzymes and decreased GSH levels along with increased thiobarbituric-acid-reactive substances and 8–hydroxy-2-deoxyguanosine (8-OHdG) levels in lymphocytes. The antioxidants and biomarkers of lipid and protein damage after dialysis sessions with HFR were similar or better than following HD-PS. Thus, the blood GPX activity was comparable to that of healthy controls and significantly better than following HD-PS. An increase in 8-OHdG levels was observed in the HD-PS group after dialysis but not in the HFR group. Conclusions: These results show that HFR induces less oxidative stress than HD-PS.

In the last few years haemodiafiltration with on-line regeneration of ultrafiltrate (HFR) has been shown to have a positive impact on inflammation and oxidative stress biomarkers, but its effect on antioxidant levels and on oxidative damage to biomolecules in the long-term is still unknown. This is a randomised clinical study over 12 months involving 40 patients on haemodialysis, comparing the effect of HFR (n=25) dialysis with haemodialysis with polysulfone (HD-PS, n=15) on oxidative stress. Total antioxidant capacity, enzymatic antioxidant [superoxide dismutase (SOD), catalase and glutathione peroxidase], non-enzymatic (GSH) and biomarkers of oxidative stress (TBARs, carbonyl groups and 8-OH-dG) were evaluated. The antioxidant activity decreased in the lymphocytes of patients dialysed with HFR, with a significant decrease in the enzyme SOD. In the oxidative stress biomarkers, an increase was seen in the levels of 8-OH-dG in patients on HD-PS dialysis but not in those treated with HFR. Throughout the year the changes in antioxidant levels and biomarkers of oxidative damage in patients dialysed with HFR were generally more modest and fluctuated less than those dialysed with HD-PS. Our study indicates that, in general, long-term dialysis with HFR does not modified antioxidant parameters or increases the oxidative damage to biomolecules. The HFR showed to be a biocompatible technique for long-term dialysis.