Capnography has been recommended as an anesthetic technique and the end-tidal carbon dioxide tension (PETCO2) is available in the operating room. PETCO2 is governed by metabolism, ventilation and circulation. When the first two parameters are controlled, PETCO2 reflects the lung flow, therefore the cardiac output. Studies have shown that PETCO2 lower than 20 mmHg is invariably associated with a cardiac output less than 2 L/min, even if other hemodynamic parameters are appropriate. Further increases in the preload, reduction of the afterload, establishment of an appropriate atrioventricular synchrony or increasing inotropy is necessary to increase PETCO2 above 25 mmHg. A considerable body of literature describes the use of PETCO2 to assess the adequacy of cardiopulmonary resuscitation after cardiac arrest. Besides, attempts have been made to use PETCO2 as an alternative to the thermodilution technique for determining cardiac output. Little has been reported of its use in cardiac surgery. From June 1996 to June 1997 we have studied 200 patients, submitted to CPB suggesting that PETCO2 around 27 mmHg would indicate a cardiac output good enough to wean the patients on the cardiopulmonary circulation so long as other hemodynamic and metabolic parameters were adequate. None of the patients required CPB giving us the impression that end-tidal carbon dioxide tension generally indicates an appropriate cardiac output.
Extracorporeal circulation; Carbon dioxide; Cardiac output; Myocardial revascularization