Venous-to-arterial CO₂ differences and the quest for bedside point-of-care monitoring to assess the microcirculation during shock

The microcirculation is the anatomical location of perfusion and substrate exchange, and its functional impairment is of paramount importance during the state of shock. The difference in venous-to-arterial carbon dioxide partial pressures (Pv-aCO₂) has recently been reported to correlate with microcirculatory dysfunction during early septic shock with greater fidelity than global hemodynamic parameters. This makes it a potential candidate as a point-of-care test in goal directed therapy that aims to restore microcirculatory function in an emergency clinical context. This early work needs to be explored further, and a better understanding of Pv-aCO₂ during the resuscitation and subsequent patient progression is required. The quest for an ideal bedside point-of-care test for microcirculatory behavior is ongoing, and is likely to consist of a combination of non-invasive sublingual microcirculatory monitoring and biochemical tests that reflect tissue perfusion. These tools have the potential to provide more accurate and clinically relevant data with regards to the microcirculation that more conventional resuscitative monitoring such as blood pressure, cardiac output, and serum lactate.