Biocompatibility of predilution on-line hemodiafiltration

In the previous papers, we reported that predilution hemodiafiltration (HDF) has more beneficial effects on dialysis patients than postdilution HDF. The mechanism behind this has not yet been clarified, but some factors could explain the advantage, such as a well-balanced solute removal pattern, reduction in the small nutrient loss and biocompatibility. Generally, the efficacy of small solute and low-molecular-weight protein removal is better in postdilution HDF or hemodialysis than in predilution; however, the more efficient removal does not always lead to the improvement of patients' symptoms and feelings. This issue suggests that the biocompatibility is an essential aspect for evaluating the quality of dialysis modality. There are three possible mechanisms for the advantages of predilution on-line HDF in biocompatibility. First, a large amount of filtrate at the filter could drain away chemical-eluting substances from the dialysis membrane and some reactive proteins. Second, blood dilution could reduce the chance of blood cells to be in close contact with the dialysis membrane surface, and then it could reduce the sequential inflammatory response. Third, blood dilution itself reduces the production of free radicals. We believe the biocompatibility of predilution online HDF is closely related to the improvement of dialysis-related various symptoms.