Novel Method for Osmotic Conductance to Glucose in Peritoneal Dialysis

Abstract Introduction The osmotic conductance to glucose (OCG) is a crucial determinant of ultrafiltration (UF) in peritoneal dialysis (PD) patients, and can be used to monitor membrane integrity in patients on long-term PD. It has been proposed that OCG can be assessed based on drained volumes in two consecutive 1-h glucose dwells, usually 1.5% and 4.25% glucose, in a so-called double mini-peritoneal equilibration test (dm-PET). However, recent data indicated that the dm-PET provides a poor estimate of OCG unless the residual volume (RV) is taken into account. Here we introduce an easy, robust and accurate method to measure OCG and compare it to conventional methods. Methods In a prospective cohort of 21 PD-patients, a modified version of the dm-PET was performed, along with determination of RV before, between and after dwells. Based on computer simulations derived from the three-pore model for membrane permeability, we developed and validated a novel single-dwell method to estimate OCG. We next validated the equation in an independent cohort consisting of 32 PD-patients. Results Single dwell OCG correlated more closely with actual ultrafiltration (r=0.94 versus r=0.07 for conventional dm-PET), sodium sieving and free-water transport compared to other methods. These findings were replicated in the validation cohort, in which OCG calculated using the single dwell method closely correlated with parameters of osmotic water transport, even when RV was not taken into account, using only drained volumes. Conclusion We propose a novel, easy and robust single dwell method to determine OCG in individual patients, and to monitor membrane integrity over time on PD.