UMEM Educational Pearls

Title: ABG vs. VBG

Posted: 12/27/2011 by Mike Winters, MBA, MD (Updated: 11/25/2024)
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VBG to Assess Respiratory Function?

Arterial blood gas (ABG) analysis is often used in to evaluate pulmonary function in critically ill ED patients.
In recent years, venous blood gas (VBG) analysis has replaced ABG analysis for assessing acid-base status (pH, HCO₃^-) in conditions such as DKA.
Some key points about the VBG for assessing pulmonary function:
- VBG does not replace an ABG in determining the exact P_aO₂
- The agreement between the VBG and ABG PCO₂ is often poor and unpredictable
- There is emerging literature on the use of VBG PCO₂ as a screen for hypercarbia but more data is needed
Bottom line: With the possible exception of screening for hypercarbia, VBG has limited utility in the assessment of pulmonary function.

Kelly AM. Can venous blood gas analysis replace arterial in emergency medical care? Emerg Med Australasia 2010;22:493-498.