Total and ionized magnesium testing in the surgical intensive care unit – Opportunities for improved laboratory and pharmacy utilization

Daniel Dante Yeh, Nalin Chokengarmwong, Yuchiao Chang, Liyang Yu, Colleen Arsenault, Joseph Rudolf, Elizabeth Lee-Lewandrowski, Kent Lewandrowski

Research output: Contribution to journalArticlepeer-review

14 Scopus citations


Purpose Ionized fraction (iMg) is the physiologically active form of magnesium (Mg); total Mg may not accurately reflect iMg status. Erroneously “low” Mg levels may result in unnecessary repetitive testing. Materials and methods From 11/2015 to 01/2016, patients ordered for Mg from a pilot ICU also had iMg tested. Weighted kappa statistic was used to assess agreement between Mg categories (low, normal, high). Predictors of unnecessary repeated Mg testing and repletion using data were explored through logistic regression models using GEE techniques to account for repeated measurements in both bivariate and multivariable analyses. Results There were 470 Mg/iMg paired measurements from 173 patients. The weighted kappa statistic was 0.35 (95%CI 0.27–0.43) indicating poor agreement in assessment of magnesium status. Of the 34 Mg samples reported as “low”, only 6 (18%) were considered “low” using concurrent iMg testing. In the multivariable models, history of atrial fibrillation (aOR = 1.61, 95%CI 1.16–2.21, p = 0.004) and concomitant metoclopramide (aOR = 1.71, 95%CI 1.03–2.81, p = 0.036) were significant predictors of unnecessary repeat Mg testing. Conclusions In the surgical ICU, categorical agreement (low, normal, high) was poor between Mg and iMg. Over 80% of “low” total Mg values are erroneous and may result in unnecessary additional measurements and repletion.

Original languageEnglish (US)
Pages (from-to)147-151
Number of pages5
JournalJournal of Critical Care
StatePublished - Dec 2017
Externally publishedYes

Bibliographical note

Funding Information:
Funding: This work was supported by Nova Diagnostics (Waltham, MA, USA). The sponsor provided reagents and testing equipment but did not have any role in the design, execution, data collection, data analysis, or manuscript preparation.

Publisher Copyright:
© 2017 Elsevier Inc.

Copyright 2018 Elsevier B.V., All rights reserved.


  • Ionized magnesium
  • Magnesium
  • Metoclopramide


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