Fluid and Solute Transport using Different Sodium Concentrations in Peritoneal Dialysis Solutions

Abstract

Background Fluid and sodium balance is important for the success of long-term peritoneal dialysis. Convective transport is the major determinant for sodium removal during peritoneal dialysis using conventional dialysis solutions. However, recent studies showed that lower sodium concentration in dialysate could significantly increase sodium removal by increasing the diffusion gradient, thereby increasing diffusive transport. In the present study, we investigated the influence of the sodium concentration gradient on the diffusive transport coefficient, KBD for sodium. Methods A 4-hour dwell study was done in Sprague–Dawley rats using 25 mL 5% glucose (NS), 5% glucose + 0.3% NaCl (LS), 5% glucose + 0.6% NaCl (MS), or 5% glucose + 0.9% NaCl (HS), with frequent dialysate and blood sampling. Radiolabeled human albumin (RISA) was added to the solution as an intraperitoneal volume marker. The peritoneal fluid and sodium transport characteristics were evaluated. Results Significant ultrafiltration (both net ultrafiltration and transcapillary ultrafiltration) was observed in each group despite the osmolality of the 5% glucose solution being slightly lower than the plasma osmolality. There was no difference in peritoneal fluid absorption rate and direct lymphatic absorption among the four groups. With the sieving coefficient for sodium set to 0.55, a significantly higher KBD for sodium was found in the NS compared to the HS group. The KBD for sodium was 0.21 ± 0.01, 0.20 ± 0.01, 0.17 ± 0.01, and 0.09 ± 0.01 mL/min for the NS, LS, MS, and HS groups, respectively. The KBD values for glucose were significantly lower in the NS and LS groups compared to the MS and HS groups. Conclusions Our results suggest that ( 1 ) sodium concentration may affect peritoneal sodium KBD — as the sodium concentration gradient increased, the KBD decreased; ( 2 ) 5% glucose solution could induce significant peritoneal ultrafiltration in normal rats despite its initial hypo-osmotic nature, this was due to the significantly lower glucose transport rate than sodium transport rate; and ( 3 ) a lower dialysate sodium concentration may decrease peritoneal glucose absorption.

Fluid and Electrolyte Transport across the Peritoneal Membrane during CAPD According to the Three-pore Model

“…It should, however, be pointed out that if the (peritoneal) diffusion gradient for sodium is large then there seems to be a "normalization" of the PS value toward that predicted by the three-pore model. This was recently discussed at some length by Cheng et al (68). Actually, it was already found by Knochel (69) that peritoneal transport of Na + in dogs was as fast as that for urea and creatinine if the dialysis fluid (5% glucose) contained no Na + , that is, if the Na + gradient between plasma and dialysate was large.…”

Single-dwell treatment with a low-sodium solution in hypertensive peritoneal dialysis patients

“…6 However, although water and Na are removed continuously during PD, patients nevertheless remain in a state of overhydration related to net Na imbalance. 7,8 By lowering the Na concentration of the dialysis fluid, [9][10][11][12] Na elimination can be improved through diffusive transport from blood to the peritoneal cavity. A previous clinical study investigated the most adequate composition (Na/glucose) in a 2-month treatment with Na concentrations of 115 and 102 mmol/L, with and without the adjustment of glucose concentration.…”