Esophageal Doppler monitor determinations of cardiac output and preload during cardiac operations

Abstract

Background. Perioperative management of cardiac surgical patients frequently mandates measurements of cardiac output and left ventricular filling. This study compared cardiac output and left ventricular filling measured by pulmonary artery (PA) catheter and esophageal Doppler monitor (EDM). Methods. Thirty-four patients undergoing coronary artery bypass grafting were prepared by implanting a PA catheter, an EDM, and a transit-time ultrasonic flow probe around the ascending aorta. In 20 patients, left ventricular end-diastolic short-axis area (EDA) was measured by transesophageal echocardiography. At five time points, cardiac output was measured from the flow probe, the EDM, and the PA catheter (by thermodilution), and left ventricular filling was assessed from the PA catheter (as PA diastolic pressure), the EDM (corrected flow time), and the EDA. For cardiac output, concordance correlations relating EDM to flow probe and PA catheter to flow probe were calculated, transformed (Fisher’s z transformation), and compared by Student’s t test. For left ventricular filling, regression coefficients were created between corrected flow time and EDA and between PA diastolic pressure and EDA. Spearman correlations were compared by Wilcoxon rank sum test. Results. The EDM and the PA catheter exhibited similar relationships to the flow probe (concordance correlations, 0.55 ± 0.35 [mean ± standard deviation] and 0.49 ± 0.34, respectively; p = 0.088). The correlation between corrected flow time and EDA was better than the correlation between PA diastolic pressure and EDA (concordance correlations, 0.49 ± 0.55 versus 0.10 ± 0.43, respectively; p < 0.01). Conclusions. These data suggest that the EDM may offer a less invasive technique for evaluating cardiac output and a more accurate estimate for preload compared with the PA catheter.