Study on the Repeatability of Cardiac Output Measurements Dependence of Temperature of Injectate

This study tests the reliability of thermodilution cardiac output measurements with pulmonary artery catheters in immediate connection with heart surgery. In accordance with our clinical practice, thermal indicator injections are synchronized with respiration. The impact on measurement repeatability of spontaneous vs artificial ventilation and the effect of the injectate temperature is tested. The study hypothesis is that when injections are synchronized with the respiration, only three injections at room temperature are needed to be within 5 % of the "true" cardiac output in mechanically ventilated patients.