Venous-to-arterial carbon dioxide difference: an experimental model or a bedside clinical tool?

Excerpt

In the present issue of Intensive Care Medicine, Ospina-Tascón et al. present an intriguing observational study in which they assessed the association between venous-to-arterial carbon dioxide difference (Pv-aCO₂) and microvascular perfusion in patients with early septic shock [1]. A total of 75 adult patients with septic shock from a 60-bed mixed ICU in Columbia were included in the study. Potentially eligible patients with septic shock in the ICU were screened, and those eligible had a pulmonary artery catheter (PAC) inserted and were included in the study. Arterial and mixed venous blood samples were collected at the insertion of the PAC (T0) and at 6 h (T6), and Pv-aCO₂ was defined as the difference between mixed-venous and arterial CO₂ partial pressures. A sidestream dark-field imaging device was used to evaluate the microcirculation of the tongue at T0 and T6, and the association between Pv-aCO₂ and the microcirculation of the tongue was assessed. Furthermore, the association between Pv-aCO₂ and global haemodynamic variables was evaluated. The authors conclude that Pv-aCO₂ was closely related to microcirculatory blood flow parameters during the early phase of septic shock, whereas Pv-aCO₂ was poorly related to systemic haemodynamic variables [1]. …