Fourth Generation FloTrac Software Pulse Contour Analysis for Measuring and Trending Cardiac Output: A Method Comparison Study.

Background: Accurate cardiac output assessment is crucial for evaluating hemodynamic status and guiding therapeutic interventions. The fourth generation FloTrac software (the FloTrac method) provides minimally invasive, continuous, and real-time cardiac output estimations. This study aimed to evaluate the accuracy, precision, and trending performance of cardiac output measurements using the FloTrac method compared to bolus thermodilution cardiac output derived from a pulmonary artery catheter (the thermodilution method).

Methods: This prospective clinical interventional study included 41 cardiac surgery patients from September 2023 to September 2024 at Aarhus University Hospital, Denmark. Cardiac output was measured simultaneously using both the FloTrac method and thermodilution method, before and after two preload-increasing interventions: a modified Trendelenburg maneuver and a fluid bolus administration. Bias, limits of agreement, and percentage error between the methods were assessed for each time point. Trending ability was evaluated using four-quadrant plots and concordance rates. Interchangeability of the two methods was accepted with a bias within the range of ±0.5 L/min, PE < 30%, and concordance rates ≥ 90%.

Results: Bias ranged from -0.36 to 0.79 L/min depending on the intervention, with consistently wide limits of agreement. Percentage errors were 37% and 35% before and after fluid administration, and 37% and 42% before and after the Trendelenburg maneuver. The concordance rate was 85% after fluid administration and 72% after the modified Trendelenburg maneuver. The FloTrac method identified fluid responders with a sensitivity of 23% and specificity of 84% with the thermodilution method as reference.

Conclusion: The FloTrac method did not meet the criteria for interchangeability with the thermodilution method for measuring cardiac output in patients after cardiac surgery. Percentage errors were unacceptable for all time points.

Editorial Comment: This study assessed an updated version of the FlowTrac cardiac output estimation system, comparing results in clinical cases with some modest preload variation to same time cardiac output measurement with pulmonary artery-based thermodilution measurements. The findings showed that there was limited agreement between these two methods in these settings, suggesting that they do not appear to be interchangeable.