Comparison of noninvasive electrical cardiometry and transpulmonary thermodilution for cardiac output measurement in critically ill patients: a prospective observational study.

Abstract

Background: Cardiac output (CO) monitoring is essential for diagnosing and managing critically ill patients. Recently, a non-invasive haemodynamic monitoring technique, electrical cardiometry (EC), has gathered increasing interest among ICU physicians. This study aimed to explore the accuracy of CO estimated by non-invasive EC (CO_EC) compared to CO determined by transpulmonary thermodilution (CO_TPTD) and to evaluate the ability of CO_EC to track CO_TPTD changes (ΔCO_TPTD).

Methods: This prospective, observational, single-center study was conducted from April 2021 to April 2023, involving patients who required haemodynamic monitoring using a transpulmonary thermodilution device (PiCCO). CO_TPTD and CO_EC were recorded simultaneously, with the investigators obtaining the CO_EC measurements were blinded to the CO_TPTD results and vice versa. Agreement between the methods was evaluated using Bland-Altman analysis and percentage error (PE). The ability of CO_EC to track changes in CO_TPTD was examined using four-quadrant and polar plots.

Results: Seventy-two patients with PiCCO haemodynamic monitoring were included, yielding 285 paired CO measurements. The bias between CO_EC and CO_TPTD was 0.47 L/min, with a limit of agreement (LoA) ranging from -2.91 to 3.85 L/min and a PE of 54.0%. Among 212 pairs of ΔCO data, excluding a central zone of 15% in the four-quadrant plot, the concordance rate between ΔCO_EC % and ΔCO_TPTD % was 70%. In the polar plot, excluding a central zone with a radius of 0.625 L/min (10% of the mean CO_TPTD), the mean polar angle for ΔCO_EC was 2.2°, with a radial LoA of 56.0°. Exploratory subgroup analysis indicated a PE of 47.0% between CO_EC and CO_TPTD and a concordance rate of 72% between ΔCO_EC% and ΔCO_TPTD% in patients with normal CO (CO ≥ 4 L/min). In patients with elevated thoracic fluid content (TFC > 35 kΩ), the PE between CO_EC and CO_TPTD was 45.0%, with a concordance rate of 64% between ΔCO_EC% and ΔCO_TPTD%. Additionally, in patients receiving low-dose norepinephrine equivalents (NEE ≤ 0.25 μg/kg/min), CO_EC and CO_TPTD exhibited a PE of 45.0%, while ΔCO_EC% and ΔCO_TPTD% achieved a concordance rate of 75% and a radial LoA of 44.2°.

Conclusion: In critically ill patients, non-invasive EC indicated limited accuracy in measuring CO, along with a restricted ability to reliably track CO changes. These findings suggested that EC may not be interchangeable with TPTD in the general ICU population.