• Karina Takesaki Miyaji, Roberto Iara Buscati, Antônio José Arraiz Rodriguez, Luciano Brandão Machado, Luiz Marcelo Sá Malbouisson, and Maria José Carvalho Carmona.
• Faculdade de Medicina, Universidade de São Paulo.
• Rev Bras Anestesiol. 2004 Oct 1; 54 (5): 625-33.

Background And ObjectivesEnd-tidal carbon dioxide (P ET CO2) not only reflects pulmonary ventilation but also carbon dioxide production (metabolism) and pulmonary blood supply (circulation). During constant metabolism and ventilation, P ET CO2 reflects pulmonary blood perfusion, thus cardiac output (CO). This study aimed at evaluating the correlation between P ET CO2 levels and CO during cardiac surgery with cardiopulmonary bypass (CPB).MethodsParticipated in this study 25 patients submitted to coronary artery bypass grafting (CABG) with CPB. End-tidal CO2 monitoring started after tracheal intubation. Cardiac output was determined by thermodilution with pulmonary artery catheter (Swan-Ganz). Carbon dioxide partial blood pressure (PaCO2) was obtained with arterial blood gases analysis. Studied parameters were evaluated in the following moments: immediately after general anesthesia induction, before cardiopulmonary bypass, at cardiopulmonary bypass completion and at surgery completion.ResultsStatistical analysis has not shown correlation between P ET CO2 and CO2, or between P ET CO2-PaCO2 gradient (Ga-eCO2) and CO. There has been correlation between P ET CO2, Ga-eCO2 and CO values variation as compared to baseline values before CPB, with loss of correlation after CPB until surgery completion.ConclusionsIn this study, where patients submitted to cardiac surgery with CPB were evaluated, ventilation/perfusion changes throughout the procedure might have been the factors determining decreased correlation between cardiac output and end tidal CO2.

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