Peritoneal Fluid and Solute Transport with Different Polyglucose Formulations

Abstract

Objective To study peritoneal fluid and solute transport characteristics using different polyglucose solutions with and without the addition of glucose. Design Thirty-one rats were divided into three groups. A 4-hour dwell study with frequent dialysate and blood samples was performed in each rat using 25 mL of 7.5% polyglucose solution (PG, n = 11),7.5% polyglucose + 0.35% glucose solution (PG1, n = 12), or 3.75% polyglucose + 1.93% glucose solution (PG2, n = 8). Radiolabeled human albumin (RISA) was added to the solutions as an intraperitoneal volume (IPV) marker. In addition, polyglucose degradation was evaluated ex vivo over 24 hours. Experimental Animals Thirty-one male Sprague Dawley rats (300 g) were used. Main Outcome Measures Fluid and solute (glucose, urea, sodium, potassium, and total protein) transport characteristics as well as changes in dialysate osmolality were evaluated. Results The IPV was higher in the PG1 and PG2 groups than in the PG group during the first 2 hours of the dwell. The IPV, in fact, decreased during the first hour of the dwell in the PG group. However, the net ultrafiltration at 4 hours tended to be lower in the PG2 (3.2 ± 1.5 mL) group compared to the PG (5.1 ± 2.3 mL) and the PG1 groups (5.2 ± 2.1 mL) (p = 0.07), and no significant difference was found between the PG and PG1 groups. Adding glucose to the PG solution increased the RISA elimination rate (KE, representing the fluid absorption rate from the peritoneal cavity): 25.5 ± 8.2, 37.5 ± 12.2, and 42.5 ± 8.9 μL/ min for the PG, PG1, and the PG2 group, respectively, p < 0.01. Dialysate osmolality (Dos) increased with the dwell time in the PG and PG1 groups but decreased in the PG2 group. The increase in Dos was partially due to the degradation of glucose polymer, which was supported by the marked increase in osmolality over 24 hours of incubation of PG solution with peritoneal fluid, ex vivo. The diffusive mass transport coefficient for the investigated solutes did not differ among the three groups (except for glucose, which was significantly lower in the PG group). The sieving coefficient for sodium was significantly higher in the PG group compared to the PG1 group (p < 0.05). Conclusion Our results suggest that, although there was an initial decrease in the intraperitoneal dialysate volume, significant amounts of fluid can be removed by polyglucose solution during a single 4-hour dwell in rats, despite the low osmolality of the solution. The positive fluid removal induced by the PG solution is partially due to the lower fluid absorption rate associated with this solution and may, to some extent, also be due to the degradation of glucose polymer within the peritoneal cavity, resulting in increased dialysate osmolality. The addition of glucose to the polyglucose solution does not seem to improve ultrafiltration in a 4-hour dwell in the rat model. However, the peritoneal fluid absorption rate may be increased, and peritoneal transport of glucose and sodium may be altered, by adding glucose to the polyglucose solution.

Ultrafiltration Characteristics of Glucose Polymers with Low Polydispersity

“…Rabbit models have been used for decades to evaluate PD solutions and peritoneal transport (15)(16)(17)(18)(19), but no such evaluations of dialysis solutions containing glucose polymers as osmotic agents have been published, except for our previous work in abstract form (10). There are two advantages to using a rabbit model, compared with a rat model, to evaluate dialysis solutions containing glucose polymers as osmotic agents: • The kinetics of UF in rat models of PD using icodextrin as the osmotic agent have been reported to differ significantly from those in human PD (13,(20)(21)(22).…”

Membrane Transport of Several Ions During Peritoneal Dialysis: Mathematical Modeling

“…In this study, we investigate a simple model of diffusive and convective transport of three ions, with the transport parameters and concentrations characteristic for PD. Mathematical modeling and computer simulation are introduced to explore and illustrate the importance of the ion–ion interaction in transmembrane transport during PD dwell and the impact of this type of interaction on estimated transport parameters that are often used to compare various group of patients or various PD fluids (23). As it is very difficult to measure the concentration profiles inside the membrane/tissue and there is no method to isolate several ions from other interactions in living tissues, this kind of modeling cannot be directly tested.…”

Long Peritoneal Dialysis Dwells With Icodextrin: Kinetics of Transperitoneal Fluid and Polyglucose Transport

“…Flame photometry measures the total sodium content in the sample and includes also the not dissociated sodium that is about 4% of total sodium, whereas our measurements performed with direct ion selective electrode report the concentration of diffusible sodium ion; the concentration of diffusible sodium ion in the study by Freida et al might be even lower than in our study. Unfortunately, the other studies discussed here did not provide measurements in fresh dialysis fluid (Wang et al, 1998a, 2000; Freida et al, 2007; Galach et al, 2009). During dwells with glucose based solutions, sodium in dialysate is also far from equilibration with plasma sodium after 360 min in patients and, furthermore, in rats after 240 min, no sodium equilibration is observed for both glucose- and icodextrin-based fluids (Wang et al, 1997, 2000).…”

“…After 12 h of the peritoneal dwell, the sodium concentration in dialysate was still by 5 mmol/L lower than that in plasma (Moberly et al, 2002). Experimental studies in rats demonstrated that the initial sodium concentration in dialysate (i.e., its concentration at third minute after fluid infusion) is similar for glucose and icodextrin based fluids in the control group and in the group with induced peritonitis separately (Wang et al, 2000), and the initial sodium dialysate to plasma ratio is not different if the mixture of icodextrin and glucose is applied as osmotic agent (Wang et al, 1998a). The initial sodium concentration was in the control group of animals around 131 mmol/L that was lower than the nominal concentration of sodium ions in icodextrin fluid of 133 mEq/L (Wang et al, 2000).…”

“…No tendency to equilibration between dialysate and plasma sodium up to 900 min of peritoneal dwell was observed (Freida et al, 2007; Galach et al, 2009). In all these studies, the sodium concentration was measured by flame photometry (Wang et al, 1998a, 2000; Freida et al, 2007; Galach et al, 2009), and in animal studies, plasma concentrations were corrected to plasma water (Waniewski et al, 1992; Wang et al, 1998a, 2000). Flame photometry measures the total sodium content in the sample and includes also the not dissociated sodium that is about 4% of total sodium, whereas our measurements performed with direct ion selective electrode report the concentration of diffusible sodium ion; the concentration of diffusible sodium ion in the study by Freida et al might be even lower than in our study.…”