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The Relation Between Body Size and Normalized Small Solute Clearances in Continuous Ambulatory Peritoneal Dialysis

ANTONIOS H. TZAMALOUKAS^*, GLEN H. MURATA^*, BETH PIRAINO, DEEPAK MALHOTRA, JUDITH BERNARDINI, PANDURANGA RAO^§ and DIMITRIOS G. OREOPOULOS^§

^* Renal Section and General Internal Medicine Section, Veterans Affairs Medical Center and Department of Medicine, University of New Mexico School of Medicine, Albuquerque, New Mexico
Renal and Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
Division of Nephrology, Department of Medicine, Medical College of Ohio, Toledo, Ohio
^§ Division of Nephrology, The Toronto Hospital, University of Toronto, Toronto, Ontario, Canada.

Correspondence to Dr. Antonios H. Tzamaloukas, Renal Section (111C), VA Medical Center, 1501 San Pedro, SE, Albuquerque, NM 87108. Phone: 505-265-1711, ext. 2418; Fax: 505-256-2803; E-mail: Tzamaloukas.Antonios_H_{at}Albuquerque.va.gov

Abstract. The normalized peritoneal clearances of small solutes depend on the ratio of their concentration in dialysate and plasma (D/P) and the drain volume (Dv) corrected for some measure of body size such as body water (V) or body surface area (BSA). The clearance formulas (D/P) x (Dv/V) and (D/P) x (Dv/BSA) can be used to examine why large individuals tend to be underdialyzed. Large people have low normalized drain volumes (Dv/V, Dv/BSA). It is not known whether size affects the D/P ratios. The purpose of this study was to examine the relationship between normalized peritoneal clearances (Kt/V_urea, C_Cr per 1.73 m² BSA) and four size indicators (weight, height, V, BSA) in 301 patients on continuous ambulatory peritoneal dialysis (four daily exchanges with 2-L exchange volume) who underwent 613 clearance studies. Highly significant (P < 0.001) nonlinear relationships were found between Kt/V_urea and weight (r² = 0.371), height (r² = 0.289), BSA (r² = 0.436), and V (r² = 0.527); and between C_Cr and weight (r² = 0.178), height (r² = 0.115), BSA (r² = 0.199), and V (r² = 0.151). There were also significant negative correlations between the normalized drain volumes (Dv/V and Dv/BSA) and all four indicators of body size. Raw (not normalized) peritoneal clearances and drain volumes correlated positively with size. However, D/P_urea or D/P_creatinine did not vary with any size indicator except for a weak association between D/P_creatinine and V (r = 0.089, P = 0.028). This association was not confirmed when V was used to stratify subjects into quartiles, and group differences for D/P_creatinine were tested by one-way ANOVA. This study shows that the exclusive cause of the low normalized peritoneal clearances in large subjects on continuous ambulatory peritoneal dialysis is a low normalized drain volume. No evidence was found to indicate that body size influences the D/P ratio of small solutes. The portion of the variance in normalized clearance explained by size varies by size indicator and solute (urea versus creatinine).

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				S. J. Davies Peritoneal solute transport--we know it is important, but what is it? Nephrol. Dial. Transplant., August 1, 2000; 15(8): 1120 - 1123. [Full Text] [PDF]

Copyright © 2008 by the American Society of Nephrology. Online ISSN: 1533-3450 Print ISSN: 1046-6673