RESUMEN
INTRODUCTION: Despite major advances in the field of dialysis, there are still some unmet needs such as reducing inflammation through adequate depuration. It is well known that the wide spectrum of pro-inflammatory and pro-atherosclerotic uremic toxins are inefficiently removed by current dialysis techniques. Adsorption seems to be an extra tool to remove toxins, but its effect and optimization have not been widely studied. The aim of this report was to present preliminary results regarding the possibility of performing hemodiafiltration with a highly adsorptive polymethylmethacrylate membrane. METHODS: The study was first conducted in 10 patients in which the safety and feasibility of hemodiafiltration with PMMA BG-U 2.1 membrane were tested through measurement of hemolysis indices, transmembrane pressures, and dialysis adequacy. Twenty patients were prospectively observed for 18-month period in which they consecutively underwent standard hemodialysis, standard post-dilution hemodiafiltration, and polymethylmethacrylate-based post-dilution hemodiafiltration. Protein-bound uremic toxins concentrations and inflammatory markers were measured throughout the observed period. RESULTS: HDF-PMMA was inferior to HDF in convective volume, but KT/V was similar, and no differences were noted in operating pressures during the two treatments. During HDF-PMMA period of treatment, we observed a significant reduction of CPR levels, and HDF-PMMA was superior to all other treatments in hepcidin removal even if this did not significantly affect hemoglobin levels. HDF-PMMA could significantly reduce indoxyl sulfate (indoxyl) concentration over a period of 6 months but not for p-cresyl sulfate (p-cresyl). CONCLUSION: PMMA BG-U 2.1 membrane can be safely and efficiently used in hemodiafiltration. Moreover, as these preliminary results show, adding adsorption properties to convection and diffusion enabled an increased removal of indoxyl uremic toxin associated to a reduction in inflammation markers as CRP and hepcidin without any negative impact on albumin levels.
RESUMEN
Dialysis urea removal metrics may not translate into proportional removal efficiency of non-urea solutes. We show that the Kt factor (plasma volume totally cleared of any solutes) differentiates removal efficiency of non-urea solutes in different technologies, and can easily be calculated by instant blood-dialysate collections. We performed mass balances of urea, creatinine, phosphorus and beta2-microglobulin by whole dialysate collection in 4 low-flux and 3 high-flux hemodialysis, 2 high-volume post-hemodiafiltration and 7 short-daily dialysis with the NxStage-One system. Instant dialysate/blood determinations were also performed at different times, and Kt was calculated as the product of the D/P ratio by volume of delivered dialysate plus UF. There were significant differences in single session and weekly Kt (whole dialysate and instant calculations) between methodologies, most notably for creatinine, phosphorus and beta2-microglobulin. Urea Kt messured in balance studies was almost equal to that derived from the usual plasma kinetic model-based Daugirdas' equation (eKt/V) and independent V calculation, indicating full correspondence. Non-urea solute Kt as a fraction of urea Kt (i.e. fractional removal relative to urea) showed significant differences between technologies, indicating non-proportional removal of non-urea solutes and urea. Instant Kt was higher than that in full balances, accounting for concentration disequilibrium between arterial and systemic blood, but measured and calculated quantitative solute removal were equal, as were qualitative Kt comparisons between technologies. Thus, we show that urea metrics may not reliably express removal efficiency of non-urea solutes, as indicated by Kt. Kt can easily be measured without whole dialysate collection, allowing to expand the metrics of dialytic efficiency to almost any non-urea solute removed by dialysis.