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VBGs will not replace ABGs




  • 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 PaO2
    • 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
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