The Role of Venous Blood Gas Analysis in Critical Care: A Narrative Review

ABG analysis is the gold standard for assessing acid–base balance, oxygenation, and ventilation in critically ill patients, but it is invasive and associated with patient discomfort and potential complications. Venous blood gas (VBG) analysis offers a less invasive alternative, although its clinical utility remains debated. This review evaluates the current evidence on VBG analysis, exploring its correlation with ABG, clinical applications, and limitations. Studies show a strong correlation between ABG and VBG for pH and a good correlation for bicarbonate and base excess in most cases, while the correlation for pCO2 remains controversial. Predictably, pO2 values differ significantly due to oxygen consumption gradients between the arterial and venous blood. VBG analysis is especially valuable for initial assessments, monitoring therapeutic responses, and guiding resuscitation in intensive care settings. It is not merely an alternative to ABG but a complementary tool that can provide unique insights, such as mixed venous oxygen saturation (SvO2) or indices that require combined ABG and VBG data, like the pCO2 gap. This review highlights the diagnostic equivalence of VBG in appropriate contexts and advocates for its use when arterial sampling is unnecessary or impractical. Furthermore, VBG analysis could enhance patient care by enabling the timely, less invasive assessment of hemodynamic and metabolic conditions. Future research should focus on refining interpretation algorithms and expanding the clinical applications of VBG to fully realize its potential in critical care practice.