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

  • Author(s): Treger, R
  • Pirouz, S
  • Kamangar, N
  • Corry, D
  • et al.
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, PCO2, and bicarbonate. Data comparing central and peripheral VBG values were also obtained. Results: The mean arterial minus venous difference for pH, PCO2, and bicarbonate was 0.027, -3.8, and -0.80, respectively. Bland-Altman plots for agreement of pH, PCO2, 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 PCO2= 0.805 + 0.936 x venous PCO2, and arterial bicarbonate = 0.513 + 0.945 x venous bicarbonate. The mean central minus peripheral differences for pH, PCO2, and bicarbonate were not clinically important. Conclusions: Peripheral or central venous pH, PCO2, and bicarbonate can replace their arterial equivalents in many clinical contexts encountered in the ICU. Copyright © 2010 by the American Society of Nephrology.

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