Esophageal Doppler and thermodilution are not interchangeable for determination of cardiac output.

Purpose: This study compares thermodilution cardiac output (TD-CO) and esophageal Doppler cardiac output (ED-CO) during periods of hemodynamic stability and after heart stabilization during off-pump coronary artery bypass (OPCAB) surgery.

Methods: After Institutional Review Board approval, 58 patients undergoing OPCAB had simultaneous comparison of TD-CO and ED-CO at three time periods. Measurements were recorded, in a blinded manner, after probe insertion (T0), immediately before and after (T1,T2) heart displacement and before starting any pharmacological treatment (if needed) to maintain systolic blood pressure to its value before heart mobilization. Measurements were also taken before sternal closure (Tfinal).

Results: Three hundred and two pairs of data were analyzed using the Bland and Altman method. Bias, standard deviation (SD) of the bias (precision), and degree of agreement (bias +/- 2 SD) were calculated. Based on published literature, we considered that the highest degree of agreement should be < 0.5 L.min(-1) to consider both methods as interchangeable. At T0, bias and SD of bias between TD-CO and ED-CO were -0.1 +/- 1.0 L.min(-1). Immediately before heart stabilization, bias +/- SD was 0.6 +/- 1.0 L.min(-1) and after heart displacement, 0.5 +/- 0.8 L.min(-1). At Tfinal, bias +/- SD was 0.7+/- 0.7 L.min(-1).

Conclusion: Because the degree of agreement was > 0.5 L.min(-1) at all measurement periods except T0, we conclude that TD and ED are not interchangeable at any time during OPCAB surgery.