Monitoring of cardiac output and cardiac work during anaesthesia by means of pulsed ultrasound Doppler

Abstract

During anaesthesia haemodynamic measurements were performed with pulsed ultrasound Doppler in six patients with a Swan-Ganz catheter. Cardiac output (CO), heart rate (HR), arterial blood pressure (AP), systemic vascular resistance (SVR) and left cardiac work (LCW) were measured simultaneously with the velocity measurements of the bloodstream in the ascending aorta. Six to fourteen (median 9) simultaneous measurements were done in each patient. Sixty-two measurements were made. The velocity (V) and the product of velocity and heart rate (VHR) were compared with CO in order to establish a non-invasive index of the cardiac output. The product of velocity, the heart rate and the arterial blood pressure (VHRAP) was compared with LCW, showing a good correlation between VHR and CO (V = maximum velocity) (rho = median 0.85), as was the case between VHRAP and LCW (rho = 0.88). Furthermore, a negative correlation between V and SVR was found, illustrating that the velocity of the bloodstream in the aorta obviously depends on the afterload. It is concluded that pulsed ultrasound Doppler in combination with HR and AP can measure relative changes in CO and LCW.