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VOLUME 17 , ISSUE 2 ( April, 2013 ) > List of Articles


Comparison of central venous saturation by standard ABG machine versus co-oximeter: Is 18 carat as good as the 24 carat gold standard?

Suchitra Ranjit, Gayathri Subramanian, V Anitha

Keywords : co-oximeter, goal directed therapy, septic shock,Central venous saturation

Citation Information : Ranjit S, Subramanian G, Anitha V. Comparison of central venous saturation by standard ABG machine versus co-oximeter: Is 18 carat as good as the 24 carat gold standard?. Indian J Crit Care Med 2013; 17 (2):82-86.

DOI: 10.4103/0972-5229.114824

License: CC BY-ND 3.0

Published Online: 00-04-2013

Copyright Statement:  Copyright © 2013; Jaypee Brothers Medical Publishers (P) Ltd.


Aims: Aggressive therapy aimed at desired end-points of Early Goal Directed Therapy (EGDT) is the cornerstone of septic shock management. A key endpoint that improves outcomes is achieving central venous saturation (ScvO 2 ) >70%. The gold standard to measure ScvO 2 is by a co-oximeter (co-ox). Settings and Design: This prospective, observational study from a multidisciplinary pediatric intensive care unit (PICU) was conducted to assess the validity of ScvO 2 levels by standard ABG (stand ABG) machine in comparison with co-ox in conditions that shifted the oxygen dissociation curve (ODC) to the right or left in sick children and controls. Materials and Methods: Data from paired samples was tested for correlation coefficient for pH, paCO 2, paO 2, and ScvO 2. Tests for correlation (Pearson′s coefficient) and agreement (Bland-Altman analysis) were performed on ScvO 2 values obtained in various subgroups. Sensitivity and specificity for ScvO 2 values determined by standard ABG machine versus co-ox were calculated in reference to EGDT endpoints. Results: A total of 141 paired samples were collected from 82 children. Despite a statistically significant difference in the pH and ScvO 2, there was good linear correlation between these parameters. Limits of agreement between ScvO 2 measured by standard ABG machine and co-ox by Bland-Altman gave 2.3% bias with 95% CI of -24.2% to 19.5%. Sensitivity and specificity of standard ABG machine in detecting low ScvO 2 in shock was 84.21% and 93.18% respectively, while it was false positive in 4 samples. Conclusions: The less expensive standard ABG machine showed satisfactory correlation with gold standard co-ox over a range of patient conditions; however, the wide range for agreement was of concern and it performed particularly poorly in anemic patients.

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