Podcast 864: Arterial Blood Gas (ABG) vs Venous Blood Gas (VBG)

<p dir="ltr"><strong>Contributor: Aaron Lessen MD</strong></p> <p dir="ltr"><strong>Educational Pearls:</strong></p> <p dir="ltr">What is measured in an ABG/VBG?</p> <ul> <li dir="ltr" aria-level="1"> <p dir="ltr" role="presentation">Blood values for oxygen tension (pO2), carbon dioxide tension (pCO2), acidity (pH), oxyhemoglobin saturation, and bicarbonate (HCO3) in either arterial or venous blood</p> </li> <li dir="ltr" aria-level="1"> <p dir="ltr" role="presentation">Other tests can measure methemoglobin, carboxyhemoglobin, hemoglobin levels, base excess, and lactate</p> </li> </ul> <p dir="ltr">What are they used for?</p> <ul> <li dir="ltr" aria-level="1"> <p dir="ltr" role="presentation">Identification of ventilation/acid-base disturbances. For example: if a patient is in septic shock, oxyhemoglobin saturation can be used to guide resuscitation efforts (early goal- directed therapy)</p> </li> </ul> <p dir="ltr">What's the difference between an ABG and VBG?</p> <ul> <li dir="ltr" aria-level="1"> <p dir="ltr" role="presentation">One of the main differences is how the blood samples are collected. Venous blood gas is normally collected from existing venous access such as a central venous catheter. Arterial blood gases must be drawn from an artery, such as the radial artery.</p> </li> <li dir="ltr" aria-level="1"> <p dir="ltr" role="presentation">Arterial blood draws can be difficult, painful, and contraindicated in many situations.</p> </li> <li dir="ltr" aria-level="1"> <p dir="ltr" role="presentation">ABGs have traditionally provided more accurate measurements for assessing oxygenation, ventilation, and acid-base status.</p> </li> <li dir="ltr" aria-level="1"> <p dir="ltr" role="presentation">However, several studies have found that VBGs can still be used to accurately assess pH, pCO2, HCO3, lactate, sodium, potassium, chloride, ionized calcium, blood urea nitrogen, base excess, and arterial/alveolar oxygen ratio. This is supported by a recent study in 2023 in the International Journal of Emergency Medicine wh