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VOLUME 26 , ISSUE 1 ( January, 2022 ) > List of Articles

Original Article

Utility of Stewart's Approach to Diagnose Missed Complex Acid–Base Disorders as Compared to Bicarbonate-anion Gap-based Methodology in Critically Ill Patients: An Observational Study

Rohit Paliwal, Adrian Pakavakis

Keywords : Albumin-corrected anion gap, Anion gap, Bicarbonate-based ABG analysis, Stewart's approach, Strong ion difference, Unidentified strong ions

Citation Information : Paliwal R, Pakavakis A. Utility of Stewart's Approach to Diagnose Missed Complex Acid–Base Disorders as Compared to Bicarbonate-anion Gap-based Methodology in Critically Ill Patients: An Observational Study. Indian J Crit Care Med 2022; 26 (1):23-32.

DOI: 10.5005/jp-journals-10071-24077

License: CC BY-NC 4.0

Published Online: 17-01-2022

Copyright Statement:  Copyright © 2022; The Author(s).


Background: Traditional arterial blood gas (ABG) analysis may miss out on some metabolic acid–base disorders. We prospectively compared Stewart's approach in critically ill patients to traditional bicarbonate-anion gap-based methods (with and without correction for albumin) to diagnose acid–base disorders. Patients and methods: Five hundred ABG samples from medical or surgical patients in the ICU were analyzed with traditional bicarbonate-anion gap-based methodology with and without correction for albumin and Stewart's biochemical approach. The primary outcome identification of additional metabolic disorders diagnosed with Stewart's approach in comparison to bicarbonate system-based approaches. We also looked at the correlation between the strong ion gap (SIG) and the albumin-corrected anion gap (acAnion Gap). Results: Stewart's approach detected missed metabolic disorders in 58 (11.6%) blood gas results reported as “within normal limits” with the bicarbonate-uncorrected anion gap approach. In 50 (10%) of these ABGs, the acAnion Gap approach was able to diagnose the missed metabolic disorders. Thus, the albumin-corrected anion gap method had a similar diagnostic performance to Stewart's approach, as it missed additional disorders in only eight (1.6%) blood gases. Conclusion: In this study, we found that the acAnion Gap approach was similar in diagnostic performance to Stewart's approach. We feel that the corrected anion gap approach can be safely used if a ready calculator for Stewart's approach is not available.

Supplementary Material

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