Super high-flux membrane dialyzers and mortality in patients undergoing hemodialysis

Purpose of review Synthetic high-flux membranes are currently the most widely used dialyzers worldwide. In Japan, super high-flux membranes have been in widespread use for some time, but in recent years, S-type dialyzer membranes have also been reported to improve prognosis. Today, super high-flux membranes with a larger pore size make it possible to remove large-molecule toxins, such as α 1 -microglobulin. This review focuses on the prognostic benefit of super high-flux and S-type dialyzer membranes. Recent findings Until 2012, dialyzers in Japan were classified based on their β2-microglobulin (β2MG) clearance rate as type I (<10 ml/min), type II (≥10–30 ml/min), type III (≥30–50 ml/min), type IV (≥50–70), or type V (≥70 ml/min). It has been reported that type IV and V dialyzers are associated with a good prognosis. Dialyzers are now classified as type I-a, I-b, II-a, or II-b, based on a combination of β2MG clearance and the sieving coefficient for albumin. Moreover, the S-type dialyzer has been defined as having high biocompatibility, improving solute removal by adsorption, and having anti-inflammatory and antioxidant properties. Summary Type IV and V dialyzers with a β2MG clearance rate of ≥50 ml/min are considered to improve the prognosis of patients on dialysis. According to the present classification, super high-flux membranes with a β2MG clearance rate of ≥70 ml/min and S-type membranes contribute to a more favorable prognosis.