Transthoracic echocardiographic assessment of cardiac output in mechanically ventilated critically ill patients by intensive care unit physicians

Background and objectives: Transthoracic echocardiography may potentially be useful to obtain a prompt, accurate and non‐invasive estimation of cardiac output. We evaluated whether non‐cardiologist intensivists may obtain accurate and reproducible cardiac output determination in hemodynamically unstable mechanically ventilated patients. Methods: We studied 25 hemodynamically unstable mechanically ventilated intensive care unit patients with a pulmonary artery catheter in place. Cardiac output was calculated using the pulsed Doppler transthoracic echocardiography technique applied to the left ventricular outflow tract in apical 5 chamber view by two intensive care unit physicians who had received a basic Transthoracic Echocardiography training plus a specific training focused on Doppler, left ventricular outflow tract and velocity‐time integral determination. Results: Cardiac output assessment by transthoracic echocardiography was feasible in 20 out of 25 enrolled patients (80%) and showed an excellent inter‐operator reproducibility (Pearson correlation test r = 0.987; Cohen's K = 0.840). Overall, the mean bias was 0.03 L.min⁻¹, with limits of agreement −0.52 and +0.57 L.min⁻¹. The concordance correlation coefficient (ρ_c) was 0.986 (95% IC 0.966–0.995) and 0.995 (95% IC 0.986–0.998) for physician 1 and 2, respectively. The value of accuracy (C_b) of CO_TTE measurement was 0.999 for both observers. The value of precision (ρ) of CO_TTE measurement was 0.986 and 0.995 for observer 1 and 2, respectively. Conclusions: A specific training focused on Doppler and VTI determination added to the standard basic transthoracic echocardiography training allowed non‐cardiologist intensive care unit physicians to achieve a quick, reproducible and accurate snapshot cardiac output assessment in the majority of mechanically ventilated intensive care unit patients.