ASN's Mission

To create a world without kidney diseases, the ASN Alliance for Kidney Health elevates care by educating and informing, driving breakthroughs and innovation, and advocating for policies that create transformative changes in kidney medicine throughout the world.

learn more

Contact ASN

1401 H St, NW, Ste 900, Washington, DC 20005

email@asn-online.org

202-640-4660

The Latest on X

Kidney Week

Please note that you are viewing an archived section from 2020 and some content may be unavailable. To unlock all content for 2020, please visit the archives.

Abstract: PO1430

Reconsidering the Edelman Equation: Impact of Individual Total Body Cation Content and Body Weight

Session Information

Category: Fluid, Electrolyte, and Acid-Base Disorders

  • 902 Fluid, Electrolyte, and Acid-Base Disorders: Clinical

Authors

  • Vuurboom, Mart D., Amsterdam UMC Locatie AMC, Amsterdam, North Holland, Netherlands
  • Wenstedt, Eliane, Amsterdam UMC Locatie AMC, Amsterdam, North Holland, Netherlands
  • Vogt, Liffert, Amsterdam UMC Locatie AMC, Amsterdam, North Holland, Netherlands
  • Olde Engberink, Rik Hg, Amsterdam UMC Locatie AMC, Amsterdam, North Holland, Netherlands
Background

Treatment of hypo- and hypernatremia is guided by formulas that are based on the Edelman equation, including Adrogue-Madias’ and others. This equation is the result of a unique study in which serum sodium concentration ([Na+]), total body exchangeable Na+ and potassium (K+) and total body water (TBW) were measured in a highly heterogeneous population. However, the Edelman equation does not account for the recently uncovered body compartment where Na+ can be temporarily stored and released without affecting TBW.

Methods

We performed a post-hoc analysis of original data from the Edelman study. In a linear regression model, the effects of important clinical characteristics on the relation between (Nae+Ke)/TBW and serum [Na+] were examined: sex, age, body weight and presence of edema. Using piecewise regression, we analyzed differences in slope and y-intercept for increasing values of (Nae+Ke)/TBW. Serum [Na+] was calculated by multiplying serum water [Na+] by 0.93.

Results

Data was available for 85 measurements in 82 patients; 57 males, 25 females, with a mean age of 57±15 years. Serum [Na+] ranged from 103 to 150 mmol/L. The association between serum [Na+] and (Nae+Ke)/TBW was different for high and low weight categories (table). Sex, age or presence of edema did not alter the association. In piecewise regression, a significant change in slope was found at 149 mmol/L (Nae+Ke)/TBW (figure; 1.12 vs 0.56, p = 0.01).

Conclusion

The coefficients of the Edelman equation are significantly affected by weight and total body cation content. The less steep slope for the higher (Nae+Ke)/TBW and high weight groups may reflect an increase in osmotically inactive Na+ storage. This may explain the inaccuracy of Edelman based formulas in daily clinical practice.