Three-Pore Model Predictions of 24-Hour Automated Peritoneal Dialysis Therapy Using Bimodal Solutions

BackgroundRecently, bimodal peritoneal dialysis (PD) solutions containing low concentrations of Na have been shown to increase 24-hour ultrafiltration (UF) or UF efficiency (UF volume per gram of carbohydrate or CHO absorbed) and Na removal in high (“fast”) transport patients during automated PD therapy. We used computer simulations to compare UF efficiency and Na removal at equivalent 24-hour UF volumes using either a generic bimodal solution (2.27% glucose + 7.5% icodextrin) during the long dwell or an increase in the glucose concentration during the short dwells, with all solutions containing Na at the conventional concentration (132 mEq/L).MethodsThe 3-pore model has been shown to accurately predict peritoneal transport for PD solutions containing glucose or icodextrin, or both. Here, we used that model to calculate 24-hour UF volume, CHO absorption, and Na removal for high (H), high-average (HA), and low-average (LA) transport patients on automated PD. Nighttime therapy consisted of 1.36% or 2.27% glucose solution (or both), and daytime therapy consisted of either Extraneal (Baxter Healthcare Corporation, Deerfield, IL, USA) or a bimodal solution.ResultsAs expected, addition of glucose to either the long dwell or the short dwells resulted in increased UF volume and glucose absorption. The increase in UF was a function of patient transport type (bimodal range: 288 – 490 mL; short-dwell range: 323 – 350 mL), and the increase in CHO absorption was smaller with glucose added to short dwells than with bimodal solution (range: 18 – 30 g vs. 34 – 39 g). The 24-hour UF efficiency was higher when high glucose concentrations were used during short-dwell exchanges than when a bimodal PD solution was used for the long dwell (0.6 to 1.2 mL/g vs. –0.1 to 0.5 mL/g). By contrast, Na removal was lower with the short-dwell exchanges (28.3 – 30.7 mmol vs. 36.2 – 53.3 mmol), likely because of more pronounced Na sieving.ConclusionsOur modeling studies predict that generic bimodal PD solutions will provide higher Na removal but not higher 24-hour UF efficiency compared with current automated PD prescriptions using Extraneal for the long dwell and glucose-containing solutions for the short dwells. The modeling predictions from this study require clinical validation.