Hemodynamic management of cardiovascular failure by using PCO₂ venous-arterial difference

The difference between mixed venous blood carbon dioxide tension (PvCO₂) and arterial carbon dioxide tension (PaCO₂), called ∆PCO₂ has been proposed to better characterize the hemodynamic status. It depends on the global carbon dioxide (CO₂) production, on cardiac output and on the complex relation between CO₂ tension and CO₂ content. The aim of this review is to detail the physiological background allowing adequate interpretation of ∆PCO₂ at the bedside. Clinical and experimental data support the use of ∆PCO₂ as a valuable help in the decision-making process in patients with hemodynamic instability. The difference between central venous CO₂ tension and arterial CO₂ tension, which is easy to obtain can substitute for ∆PCO₂ to assess the adequacy of cardiac output. Differences between local tissue CO₂ tension and arterial CO₂ tension can also be obtained and provide data on the adequacy of local blood flow to the local metabolic conditions.