[Selective adsorption of homocysteine using HFR-on line technique]. / Estrazione di omocisteina in corso di HFR on-line.

Homocysteine (Hcy) is grossly elevated in hemodialysis (HD) patients. Treatment with folic acid and/or vitamin B12 fails to normalize Hcy levels in the majority of patients. Treatment with various dialyzers with different flux characteristics has produced contrasting results. Hemodiafiltration reinfusion (HFR) on-line (double chamber hemodiafiltration (HDF) with regenerated ultrafiltrate reinfusion) is a novel method combining the processes of diffusion, convection and absorbance. The ultrafiltrate is regenerated through a charcoal-resin device. Our aim was to observe the effect of the HFR on-line technique on removing Hcy. We investigated the effect of this treatment on Hcy levels in 10 patients with a mean Hcy level of 57.6 micromol/L (range 24.1-119.7). We measured Hcy, folate and vitamin B12 pre- and post-dialysis and in the ultrafiltrate pre- and post-cartridge at 10, 120 and 240 min. Mean Hcy levels were 57.6 and 35.3 micromol/L (range 9.9-80.3) (p=0.005) pre- and post-dialysis, respectively, while folate and vitamin B12 were unchanged. Pre- and post-cartridge Hcy levels were 11.6 vs 2.5 (p=0.005), 9.3 vs 3.9 (p=0.005), 7.7 vs 4.6 micromol/L (p=0.012) at three time points considered, while folate and vitamin B12 were essentially undetectable. These preliminary data, which need confirmation in a long-term study, seem to indicate that HFR on-line reduces Hcy levels, not only through a possible reduction in uremic toxins, but also through the actual removal of Hcy by absorbance on the charcoal-resin cartridge.