Measurement of the cardiac output is one of the important hemodynamic monitoring tools in cardiac surgery. It helps determine the type of medications needed to maintain optimal hemodynamic status in the entire perioperative period. Thermodilution method using pulmonary artery catheter is considered has the gold standard for the measurement of cardiac output. Investigators would like to compare the most popular minimally-invasive devices used to measure cardiac output using arterial waveform: LiDCO Rapid and TEE with the thermodilution method at various phases of the cardiac surgery.

Measurement of the cardiac output is one of the important hemodynamic monitoring tools in cardiac surgery. It helps determine the type of medications needed to maintain optimal hemodynamic status in the entire perioperative period. Thermodilution method using pulmonary artery catheter is considered has the gold standard for the measurement of cardiac output, however over the past 10 to 15 years it has been questioned about its safety and efficacy. There has been a surge in recent years of less invasive devices capable of measuring cardiac output by various means, including bioimpedance, transpulmonary thermodilution, transthoracic and transesophageal echocardiography, and arterial waveform analysis.

There is a variety of devices currently available for cardiac output measurement by arterial-waveform analysis. These devices have been compared to each other, and to the pulmonary artery catheter as the gold standard. However, the companies manufacturing these devices have made software upgrades that they believe improves their performance. No studies have been performed comparing the uncalibrated arterial waveform based cardiac output measurement device,LiDCORapid since the software upgrades. In addition to baseline cardiac output measurements, Investigators intend to study the effect of volume loading (by trendelenburg position), sympathetic stimulus (incision), a vasodilated state (15 minutes after separation from CPB) and chest closure on cardiac output measured by the three different techniques.

In addition to cardiac output the investigators would like to measure stroke volume ,Systemic Vascular Resistance, stroke volume variation with LiDCO . The main purpose is to validate the accuracy of measurements by these two minimally-invasive methods in comparison with thermodilution method in various hemodynamic states.

Inclusion Criteria:

• Elective cardiac procedures other than those specified in the exclusion criteria

Exclusion Criteria:

• All emergency cardiac procedures, prisoners and pregnant women, patients who are scheduled for ventricular assist devices and those with severe aortic, mitral and tricuspid insufficiency will be excluded.

All elective adult cardiac surgery patients who are scheduled in UIHC from Sep 2012 to August 2015 will be included.