Journal Article

Sodium removal and sodium concentration during peritoneal dialysis: effects of three methods of sodium measurement

Vincenzo La Milia, Salvatore Di Filippo, Monica Crepaldi, Simeone Andrulli, Lucia Del Vecchio, Pietro Scaravilli, Giovambattista Virga and Francesco Locatelli

in Nephrology Dialysis Transplantation

Published on behalf of European Renal Association - European Dialysis and Transplant Assoc

Volume 19, issue 7, pages 1849-1855
Published in print July 2004 | ISSN: 0931-0509
Published online April 2004 | e-ISSN: 1460-2385 | DOI:
Sodium removal and sodium concentration during peritoneal dialysis: effects of three methods of sodium measurement

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Background. Sodium removal (NaR) may have a major impact on the survival of peritoneal dialysis patients. The dialysate/plasma sodium concentration ratio (D/PNa) is an indirect index of transcellular water transport by aquaporin channels, and thus of ultrafiltration. Sodium concentration can be assessed by means of flame photometry (F), and direct (D-ISE) or indirect ion-selective electrodes (I-ISE), but these methods have different properties. I-ISE is being used increasingly in clinical laboratories. The aim of this study was to evaluate NaR and D/PNa using the three different measurement methods.

Methods. We performed peritoneal equilibration tests (PETs) in 44 peritoneal dialysis patients and calculated the NaR. We also calculated D/PNa during the test; plasma and dialysate sodium concentrations were measured by F, D-ISE and I-ISE.

Results. NaR was lower (P<0.001) with D-ISE (69±29 mmol) than with F (81±29 mmol) or I-ISE (79±28 mmol). D/PNa was also lower at baseline (0.92±0.02 vs 0.95±0.02 and 0.95±0.02; P<0.001), after 60 min (0.87±0.03 vs 0.90±0.03 and 0.90±0.03; P<0.001) and at the end of PET (0.88±0.04 vs 0.92±0.04 and 0.92±0.04; P<0.001) when measured by D-ISE in comparison with F and I-ISE, respectively.

Conclusions. NaR and D/PNa were lower when measured by the D-ISE method compared with the F and I-ISE methods. NaR and D/PNa were similar when measured by F or I-ISE. I-ISE can be used reliably in the evaluation of NaR and D/PNa in everyday clinical practice of peritoneal dialysis.

Keywords: flame photometry; ion-selective electrode; peritoneal dialysis; sodium concentration; sodium removal; sodium gradient

Journal Article.  3951 words.  Illustrated.

Subjects: Nephrology

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