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Comparative Study
. 2010 Mar;5(3):390-4.
doi: 10.2215/CJN.00330109. Epub 2009 Dec 17.

Agreement between central venous and arterial blood gas measurements in the intensive care unit

Richard Treger  1 , Shahriar Pirouz, Nader Kamangar, Dalila Corry
Affiliations
Comparative Study

Agreement between central venous and arterial blood gas measurements in the intensive care unit

Richard Treger et al. Clin J Am Soc Nephrol. 2010 Mar.

Abstract

Background and objectives: Venous blood gas (VBG) analysis is a safer procedure than arterial blood gas (ABG) analysis and may be an alternative for determining acid-base status. The objective of this study was to examine the agreement between ABG and central VBG samples for all commonly used parameters in a medical intensive care unit (ICU) population.

Design, setting, participants, & measurements: We performed a single-center, prospective trial to assess the agreement between arterial and central VBG measurements in a medical ICU. Adult patients who were admitted to the ICU and required both a central venous line and an arterial line were enrolled. When an ABG was performed, a central venous sample was obtained to examine the agreement among the pH, Pco(2), and bicarbonate. Data comparing central and peripheral VBG values were also obtained.

Results: The mean arterial minus venous difference for pH, Pco(2), and bicarbonate was 0.027, -3.8, and -0.80, respectively. Bland-Altman plots for agreement of pH, Pco(2), and bicarbonate showed 95% limits of agreement of -0.028 to 0.081, -12.3 to 4.8, and -4.0 to 2.4, respectively. Regression equations were derived to predict arterial values from venous values as follows: Arterial pH = -0.307 + 1.05 x venous pH, arterial Pco(2) = 0.805 + 0.936 x venous Pco(2), and arterial bicarbonate = 0.513 + 0.945 x venous bicarbonate. The mean central minus peripheral differences for pH, Pco(2), and bicarbonate were not clinically important.

Conclusions: Peripheral or central venous pH, Pco(2), and bicarbonate can replace their arterial equivalents in many clinical contexts encountered in the ICU.

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Figures

Figure 1.
Figure 1.
Bland-Altman plot of arterial and central venous blood pH showing the regression line (solid line) and the 95% limits of agreement of −0.028 to 0.081 (dotted lines) for the A-V difference. r = 0.296, R2 = 0.088.
Figure 2.
Figure 2.
Bland-Altman plot of arterial and central venous blood Pco2 showing the regression line (solid line) and the 95% limits of agreement of −12.3 to 4.8 mmHg (dotted lines) for the A-V difference. r = −0.01, R2 = 0.0001.
Figure 3.
Figure 3.
Bland-Altman plot of arterial and central venous blood HCO3 showing the regression line (solid line) and the 95% limits of agreement of −4.0 to 2.4 mEq/L (dotted lines) for the A-V difference. r = −0.136, R2 = 0.018.
Figure 4.
Figure 4.
Correlation between central venous and arterial blood gas values for pH. R2 = 0.95.
Figure 5.
Figure 5.
Correlation between central venous and arterial blood gas values for Pco2. R2 = 0.88.
Figure 6.
Figure 6.
Correlation between central venous and arterial blood gas values for HCO3. R2 = 0.95.
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