Protein-Bound Uremic Toxin Profiling as a Tool to Optimize Hemodialysis

AIM: We studied various hemodialysis strategies for the removal of protein-bound solutes, which are associated with cardiovascular damage. METHODS: This study included 10 patients on standard (3x4h/week) high-flux hemodialysis. Blood was collected at the dialyzer inlet and outlet at several time points during a midweek session. Total and free concentration of several protein-bound solutes was determined as well as urea concentration. Per solute, a two-compartment kinetic model was fitted to the measured concentrations, estimating plasmatic volume (V(1)), total distribution volume (V(tot)) and intercompartment clearance (K(21)). This calibrated model was then used to calculate which hemodialysis strategy offers optimal removal. Our own in vivo data, with the strategy variables entered into the mathematical simulations, was then validated against independent data from two other clinical studies. RESULTS: Dialyzer clearance K, V(1) and V(tot) correlated inversely with percentage of protein binding. All Ks were different from each other. Of all protein-bound solutes, K(21)was 2.7–5.3 times lower than that of urea. Longer and/or more frequent dialysis that processed the same amount of blood per week as standard 3x4h dialysis at 300mL/min blood flow showed no difference in removal of strongly bound solutes. However, longer and/or more frequent dialysis strategies that processed more blood per week than standard dialysis were markedly more adequate. These conclusions were successfully validated. CONCLUSION: When blood and dialysate flow per unit of time and type of hemodialyzer are kept the same, increasing the amount of processed blood per week by increasing frequency and/or duration of the sessions distinctly increases removal.