From the Research
Venous pH is usually 0.05 units lower than arterial pH, as evidenced by the most recent and highest quality study 1. This difference occurs because venous blood contains more carbon dioxide, which forms carbonic acid when dissolved in blood, making venous blood slightly more acidic.
- The study published in 2021 in the journal Anesthesia and analgesia 1 found that the mean difference between arterial and central venous pH was 0.03 units in hemodynamically stable patients.
- However, the same study also derived an adjustment formula for ABG conversion from central VBG, which includes arterial pH = venous pH + 0.05 units.
- This formula suggests that venous pH is typically 0.05 units lower than arterial pH, which is consistent with the physiological differences between venous and arterial blood.
- Other studies, such as those published in 2001 2, 2012 3, and 2009 4, also support the idea that venous pH is slightly lower than arterial pH, although they may not provide an exact difference.
- A more recent systematic review published in 2023 5 highlights the importance of considering physiological differences between venous and arterial blood values and sampling procedures when comparing arterial and venous blood gas analysis.
- Overall, the evidence suggests that venous pH is usually 0.05 units lower than arterial pH, which is an important consideration in clinical practice, particularly when interpreting blood gas results and making decisions about patient care.