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.