Comparison of Simultaneously Obtained Central Venous Blood Gas and Arterial Blood Gas Analysis for pH, pCO2, BE and K+ in Patients Attending Emergency Medicine of Tertiary Care Centre

Bicarbonate (HCO3-) measurement in serum or plasma from a sample of venous blood is routinely practiced in hospital patient management. HCO3- status can also be assumed from Blood gas analysis requiring arterial blood as sample which is cumbersome for both patients and doctors. This study was undertaken to evaluate the extent of agreement among biocarbonate values obtained during venous, arterial blood gas analysis and conventionally measured serum bicarbonate levels in a group of intensive care unit (ICU) patients to determine whether conventionally measured serum HCO3- (from peripheral venous blood) and calculated HCO3-values (from arterial blood gas [ABG] analyzers) can be used interchangeably. A total of 51 adult patients with diverse medical conditions, presenting at a tertiary health centre ICU were enrolled in this study when deemed by the treating physician to have an ABG analysis. Arterial and venous samples were taken as close in time as possible for blood gas analysis and routine blood tests. Bland-Altman analyses were used to compare the three methods. The HCO3- levels from ABG, Venous Blood gas (VBG) and tconventionally measured serum HCO3- showed acceptably narrow 95% limits of agreement using the Bland-Altman method. VBG reveals higher level of agreement with the ABG bicarbonate values compared to measured serum HCO3-. Thus, venous blood can be an alternate for arterial blood where ABG analyzer is available. conventionaly serum HCO3- measurements can also be useful and used as substitute for an expensive ABG analyzer in resource constrained health care sectors when required. DOI: http://dx.doi.org/10.3329/bjmb.v5i1.13425 Bangladesh J Med Biochem 2012; 5(1): 12-15

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Comparison of measured Serum Total Carbon Dioxide with calculated Bicarbonate calculated from Arterial Blood Gas Analysis

Indian Journal of Medical Biochemistry ◽

10.5005/jp-journals-10054-0025 ◽

2017 ◽

Vol 21 (2) ◽

pp. 76-80

Author(s):

Thuthi Mohan ◽

B Vinodh Kumar

Keyword(s):

Carbon Dioxide ◽

Venous Blood ◽

Blood Gas Analysis ◽

Gas Analysis ◽

Total Carbon ◽

Blood Gas ◽

Arterial Blood Gas ◽

Arterial Blood ◽

Arterial Blood Gas Analysis ◽

Good Agreement

ABSTRACT Introduction Measured total carbon dioxide (TCO2) from venous sample and calculated bicarbonate from arterial blood gas (ABG) have shown good agreement in some studies, while conflicting results have been obtained in few other studies. The objective of this study is to compare and assess the degree of agreement between the measured TCO2 and calculated bicarbonate and also whether they can be used interchangeably in our laboratory. Materials and methods We prospectively analyzed 89 ABG samples requested for calculated bicarbonate and then measured TCO2 from venous blood samples drawn simultaneously from the same participants between November 2016 and April 2017. Results Measured TCO2 results ranged from 5.7 to 39.9 mmol/L (mean 23.45 mmol/L), while calculated bicarbonate ranged from 9 to 40 mmol/L (mean 24.36 mmol/L). The values of TCO2 and bicarbonate correlated well (r = 0.95, p < 0.001), with the correlation given by the equation, y = 0.884x + 3.605. The bias obtained was —0.9 mmol/L and the standard deviation (SD) was 1.62 mmol/L. The limits of agreement (LOA) were —4.1 to 2.3 mmol/L, with a span of 6.4 mmol/L. Out of the 89 values, 85 (95.05%) were within the LOA. Conclusion In majority of the cases, the calculated bicarbonate concentration from ABG showed a good correlation to the measured venous TCO2 concentration. Despite this excellent correlation, TCO2 did not show good agreement with calculated bicarbonate when Story and Poustie's criteria were applied, especially in cases of bicarbonate less than 20 mmol/L. Hence, clinicians should be aware of this discrepancy and be cautious when using measured TCO2 and calculated bicarbonate interchangeably in the assessment and management of acid—base disorders, especially in patients with metabolic acidosis. How to cite this article Mohan T, Kumar BV. Comparison of measured Serum Total Carbon Dioxide with calculated Bicarbonate calculated from Arterial Blood Gas Analysis. Indian J Med Biochem 2017;21(2):76-80.

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