Small and Middle Molecular Weight Solute Clearance in Nocturnal Intermittent Peritoneal Dialysis

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Abstract
Objectives: To determine the dialysate-to-plasma (D/P) concentration ratios and peritoneal dialytic clearance (ClD) of substances with a wide range of molecular weights in subjects receiving a simulated nocturnal intermittent peritoneal dialysis (NIPD) session. Design: Open-label single-dose study. Subjects: Six end-stage renal disease patients undergoing peritoneal dialysis (PD). Setting: Clinical research center of a university-affiliated hospital. Interventions: Subjects received intravenous gentamicin and vancomycin on the first day of the study. Subjects received no PD until their return on the following day, when subjects underwent a simulated NIPD session utilizing four 2- to 2.5-L peritoneal dialysate dwells of 2 hours. Blood and dialysate samples were collected immediately before the session and after each dialysate dwell for determination of urea, creatinine, gentamicin, vancomycin, and β2-microglobulin (β2M) concentrations. Each solute's D/P concentration ratio and peritoneal ClD were calculated. Measurements and Main Results: The (mean ±SD) 2-hour D/P concentration ratios were 0.78 ± 0.05 (urea), 0.49 ± 0.11 (creatinine), 0.38 ± 0.08 (gentamicin), 0.11 ± 0.06 (vancomycin), and 0.07 ± 0.03 (β2M). Peritoneal ClD values (mL/min of dialysis) were 19.0 ± 2.8 (urea), 12.1 ± 3.5 (creatinine), 8.4 ± 2.8 (gentamicin), 2.7 ± 1.5 (vancomycin), and 1.7 ± 0.8 (β2M). The D/P concentration ratios and peritoneal ClD values for urea, creatinine, and gentamicin were significantly different from vancomycin and β2M (repeated measures ANOVA, p < 0.05). β2-Micro-globulin peritoneal ClD was strongly related to gentamicin peritoneal ClD ( r = 0.96, p < 0.05). Conclusion: Small molecular weight solutes have significantly greater D/P and peritoneal ClD than middle molecular weight solutes in NIPD. In NIPD, daily peritoneal ClD of β2M is lower than that reported in continuous ambulatory PD. NIPD also results in lower drug ClD than that reported in continuous ambulatory PD studies.