A review of using CO₂-derived variables to detect tissue hypoperfusion during cardiopulmonary bypass

Complications after cardiac surgery with cardiopulmonary bypass (CPB) are associated with increased morbidity and mortality. Early detection and prompt reversion of tissue hypoperfusion during CPB are key factors to reduce organ dysfunction after cardiac surgery. CO2 (carbon dioxide)-derived variables which are easy to assess and routinely available to evaluate the adequacy of macro- and microcirculation may offer important information on the adequacy of the perfusion during CPB. However, since some practical issues remain unsolved in providing a reliable measurement of CO2 removal from the patient, CO2-derived variables are not widely monitoring during CPB. This review aims to demonstrate the basic principles of CO2-derived variables during CPB, the available techniques to assess CO2-derived variables on CPB and the clinically relevant applications.