Cardiac output determination by thermodilution and arterial pulse waveform analysis in patients undergoing aortic valve replacement

Abstract

Purpose: To compare the accuracy of cardiac output (CO) measurement by arterial pulse waveform analysis (COPW) to thermodilution assessments in patients with aortic stenosis, a high-risk patient group who may benefit from extended hemodynamic monitoring. Methods: In 30 patients with aortic stenosis, CO was assessed in triplicate by thermodilution via pulmonary artery catheterization (COPAC), and by arterial pulse waveform analysis (COPW), before and after valve replacement. The techniques were compared by assessing the repeatability coefficient of each method and by calculating the percentage error, bias, and the limits of agreement between methods. Results: The repeatability coefficients of COPAC and CO PW were 0.89 L·min-1 and 1.04 L·min -1 respectively after induction of anesthesia, which corresponded to 24% of COPAC and 26% of COPW, and increased to 33% of COPAC and 32% of COPW immediately after extracorporeal circulation. A systematic error between methods was not observed. The limits of agreement were bias ± 1.42 L·min-1 after anesthesia induction, corresponding to a 36% percentage error. The scattering of differences between methods increased markedly after termination of extracorporeal circulation (percentage error 56%). Conclusion: The repeatability of COPAC, as well as of COPW, is reduced in patients with aortic stenosis. The repeatability of both methods, as well as the agreement between methods, decreased markedly immediately after termination of cardiopulmonary bypass.