Hemodiafiltration - state of the art.

Many observational studies have consistently shown that high-flux hemodialysis (hf-HD) has positive effects on the survival and morbidity of chronic kidney disease stage 5 dialysis (CKD5D) patients when compared with low-flux hemodialysis, but the primary analysis of the prospective randomized Hemodialysis Outcomes (HEMO) study showed that the use of hf-HD was not associated with a significant reduction of the relative risk of mortality. More recently, the Membrane Permeability Outcome (MPO) study found that survival could be significantly improved by use hf-HD compared with low-flux dialysis in high-risk patients as identified by serum albumin ≤4 g/dl and, in a post-hoc analysis, in diabetic patients. Online hemodiafiltration (HDF) is reported as the most efficient technique of using high-flux membranes. Clearances of small solutes like urea are higher than in hemofiltration and of middle solutes like β(2)-microglobulin are higher than in hf-HD. As the number of randomized prospective trials comparing HDF and hf-HD is still very limited, no conclusive data are available concerning the effect of increased convection of online HDF on survival and morbidity in CKD5D patients. A large, randomized controlled study is needed to clinically confirm the theoretical advantages of online HDF.