Relationship between fill volume and transport in peritoneal dialysis-from bench to bedside

IntroductionLarger fill volumes in peritoneal dialysis (PD) typically improve small solute clearance and water removal, and vice versa-but the relationship between intraperitoneal volume and the capacities for solute and water transport in PD has been little studied. Here, it is proposed that this relative relationship is described by a simple ratio (Volume_new/Volume_old)^2/3 up to a critical break-point volume, beyond which further volume increase is less beneficial in terms of solute and water removal.MethodTo scrutinize this hypothesis, experiments were conducted in a rat model of PD alongside a retrospective analysis of data from a prior clinical study. Rats underwent PD with either three consecutive fills of 8 + 8 + 8 mL (n = 10) or 12 + 12 + 12 mL (n = 10), with 45-minute dwell time intervals. This approach yielded 60 estimations of water and solute transport, characterized by osmotic conductance to glucose and solute diffusion capacities, respectively.ResultsComparative analysis of the predictive efficacy of the two models-the simple ratio versus the break-point model-was performed using Monte Carlo cross-validation. The break-point model emerged as a superior predictor for both water and solute transfer, demonstrating its capability to characterize both experimental data from rats and clinical data from patients.ConclusionThe present analysis indicates that relatively simple calculations can be used to approximate clinical effects on solute and water removal when prescribing a lower or higher fill volume to patients with PD.