MO715: The Role of Duration and Modality Choice on Sodium and Water Removal for Peritoneal Dialysis Patients
Authors: Theodoridis Marios , Serif-Damadoglou Humeyra , Kantartzi Konstantia , Tsalikidis Christos , Passadakis Ploumis , Thodis Elias , Panagoutsos Stylianos 
Published: May 2022

Abstract

BACKGROUND AND AIMS
Hypervolemia is common in peritoneal dialysis (PD) and contributes to hypertension and left ventricular hypertrophy, thus increasing the cardiovascular risk of these patients. The achievement of adequate water and sodium balance is considered a major determinant of dialysis adequacy and seems to have a greater effect on PD outcome than Kt/V and small solute clearances. However, the contribution of different PD modalities to dialytic sodium removal remains not well defined. The aim of this study was to explore the effect of different PD modalities on sodium and water removal.

METHOD
This is a single-center cohort study of 21 patients (m = 12, f = 9). They were examined according to their modality of PD: CAPD (continuous ambulatory PD n = 9) and APD (continuous cycler PD n = 12). CAPD patients’ median age was 74 years (66–79), median time on PD was 37 months (24–59), median Kt/V 2.4 (1.9–3.1) and median eGFR 9.9 mL/min (3.5–12.4). APD patients’ median age was 47 years (32–75), median time on PD 65 months (52–87), median Kt/V 2.439 (2.12–2.8) and median eGFR 2.3 mL/min (0–5). We used the modified peritoneal equilibration test (PET with DW 4.25%) and double mini-PET to calculate the small solute transport rate (D/P of creatinine), water removal (FWT—free water transport, ΔNa—sodium dip, OCG—osmotic conductance of glucose) and mesothelial cell integrity (CA125 appearance rate in dialysis effluent). We also calculate the total amount of sodium excretion from the 24 h PD effluent collection and urine collection. Using bioimpedance spectroscopy we calculate the patients’ total body water, the overhydration and the intracellular and extracellular volume (ECV).

RESULTS
We did not find between the two groups any statistically significant difference for water movement through the membrane (ΔNa P = 0.427; FWT P = 0.384; OCG P = 0.27), for the marker of mesothelial cell mass (CA125AR P &gt; 0.05) or for hydration status (OH, ECV). There was a statistically significant difference between the two groups for the small solute transport rate (Cr d/p, P = 0.025), for the total daily amount of sodium excretion through the membrane (P &lt; 0.001), i.e. patients on APD having faster solute movement and excrete more sodium during the day compared to CAPD patients. Additionally, from the regression analysis there was statistically significant correlation between the daily dialysis sodium excretion and solute movement (P = 0.007, r = 0.58) and total time on PD (P = 0.004, r = 0.612).

CONCLUSION
These results indicate that there is no inferiority of APD compared to CAPD for sodium excretion due to the smaller time duration of the cycles (sodium sieving). Additionally, we notice that even though the patients on APD remained longer on PD and received larger daily volumes of PD effluent there was not any difference in mesothelial cell marker or water transport indicators. Inevitable time probably through neo angiogenesis results in faster solute transport.