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Impact of total body water errors on Kt/V estimates in children on peritoneal dialysis

B Morgenstern1, K S Nair, G Lerner

  • 1Mayo Clinic, Rochester, Minnesota, USA.

Advances in Peritoneal Dialysis. Conference on Peritoneal Dialysis
|August 21, 2001
PubMed

Insights

Estimating total body water (TBW) is crucial for peritoneal dialysis (PD) adequacy in children. New Pediatric Peritoneal Dialysis Study Consortium (PPDSC) formulas using H2[18O] provide more accurate TBW measurements than older methods for children on PD.

Area of Science:

  • Pediatric Nephrology
  • Dialysis Adequacy
  • Biomarkers

Background:

  • Accurate estimation of total body water (TBW) is essential for determining peritoneal dialysis (PD) adequacy, particularly Kt/V, in pediatric patients.
  • Current Dialysis Outcomes Quality Initiative (DOQI) guidelines recommend the Mellits and Cheek (MC) formulas for pediatric TBW estimation, but these were derived from healthy children and may not be suitable for those on PD.
  • Previous TBW estimation methods may lead to inaccuracies in assessing PD adequacy in children.

Purpose of the Study:

  • To evaluate the impact of different total body water (TBW) estimation methods on the calculation of Kt/V in children undergoing peritoneal dialysis (PD).
  • To compare the accuracy of established formulas (Mellits and Cheek) and newly developed formulas against direct TBW measurements in pediatric PD patients.
  • To introduce and validate new TBW estimation formulas developed by the Pediatric Peritoneal Dialysis Study Consortium (PPDSC) for children on PD.

Main Methods:

  • Prospective study involving 24 children initiating PD.
  • Direct measurement of TBW using H2[18O] (O18) as the gold standard.
  • Calculation of Kt/V using TBW estimated by H2[18O] (O18), Mellits and Cheek (MCD) formulas, and new PPDSC (NEW) formulas.

Main Results:

  • Mean weekly Kt/V values differed significantly between methods: O18 (2.2), MCD (2.0), and NEW (2.0).
  • The O18 method showed significant variation compared to both MCD and NEW estimates (p < 0.001).
  • Deviations from O18-measured Kt/V were 9.5% (max 16%) with MCD and 7.8% (max 18%) with NEW formulas, indicating substantial impact of TBW estimation method.

Conclusions:

  • Determinations of Kt/V in pediatric PD patients are significantly influenced by the method used for estimating TBW.
  • The PPDSC formulas, based on H2[18O] measurements, offer a more accurate approach to calculating TBW in children on PD compared to formulas derived from healthy children.
  • The PPDSC formulas should be adopted to replace older formulas for TBW estimation in pediatric PD patients to ensure accurate assessment of dialysis adequacy. Further validation of Kt/V as an adequacy marker requires prospective studies.

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