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

The difference between mixed venous blood carbon dioxide tension (PvCO(2)) and arterial carbon dioxide tension (PaCO2), called a dagger 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 a dagger PCO2 at the bedside. Clinical and experimental data support the use of a dagger 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 a dagger 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.