A method of comparison of different regimens for dialyzing single-pool solutes

Many points of reference have been used to compare and rationalize extracorporeal end-stage renal disease therapy. We address a specific part of the subject: the effect of the delivery schedule on a predetermined dose of dialysis, e.g., weekly Kt/V. Steady (time-invariant) application of dialysis absolutely minimizes time-averaged and peak concentrations of any extractable solute. However, such dosing is often impractical; we assess the effectiveness of achievable slow regimens relative to steady dosing, using the single-pool approximation, applicable to slow regimens. Dose scheduling has been previously considered. We combine and discuss prior observations and establish continuous dosing as an easily quantifiable reference point, and we emphasize fundamental patterns common to different schedules. Thus, we enable rapid comparison of the many "slow" dialysis regimens presently under consideration using two intuitive parameters to encompass dialysis dosing: intermittency and intensity. These parameters define any repetitive dialysis pattern. A method for evaluating any combination of them is given with formulae, graphically, and with examples. Intermittency increases average solute concentration only slightly, but the frequency and spacing of intermittent treatments strongly affect peak solute concentrations. With steadier solute removal, cycling of solvent (water) stores is likely to remain the dominant source of disequilibrium in patients.