Effect of dialyser membrane pore size on plasma homocysteine levels in haemodialysis patients

Abstract

Background. Hyperhomocysteinaemia is a putative risk factor for atherothrombotic cardiovascular disease in the haemodialysis population. High-dose vitamin B therapy does not entirely normalize elevated plasma total homocysteine (tHcy) levels in haemodialysis patients. Alternative therapies to reduce tHcy further are therefore required. Modifications of the dialysis regimen may result in a better removal of Hey. We examined the effect of dialyser membrane pore size on tHcy levels in vitamin-replete chronic haemodialysis patients. Methods. Forty-five haemodialysis patients were dialysed during 4 weeks with a low-flux, a high-flux and a super-flux membrane, in random order. Pre-dialysis tHcy was determined at baseline and every 4 weeks. In 18 patients, plasma tHcy before and after dialysis and dialysate tHcy concentrations were measured. Results. Pre-dialysis tHcy decreased significantly during 4 weeks super-flux dialysis (-14.6 ± 2.8%), whereas it remained stable during high-flux (+0.5 ± 2.4%) and low-flux dialysis (+1.7 ± 3.2%). The homocysteine reduction ratio was not different for the three membranes: 0.39 ± 0.03 for the super-flux, 0.47 ± 0.02 for the high-flux and 0.39 ± 0.02 for the low-flux dialyser. The amount of Hey recovered in the dialysate during a single dialysis session was also similar: 117.5 ± 3.6 μmol during super-flux, 95.3± 11.5 μmol during high-flux and 116.5± 11.6 μmol during low-flux dialysis. Conclusion. Super-flux dialysis significantly lowers tHcy in chronic haemodialysis patients. Improved removal of middle-molecule uracmic toxins with inhibitory effects on Hcy-metabolizing enzymes, rather than better dialytic clearance of Hey itself, may explain the beneficial effect of the super-flux membrane.