Evaluation of a modified FloTrac™ algorithm for cardiac output measurement in cardiac surgery patients

Introduction

The first evaluation studies of the FloTrac™ device (Edwards Lifesciences, USA) for cardiac output (CO) measurement revealed conflicting results [1, 2]. The initially used software version may in part be responsible for these findings. The aim of this study was to compare the CO determined by FloTrac™ using software versions 1.03 and 1.07 (aFCO and bFCO) with the CO measured by PiCCOplus™ (Pulsion Medical Systems, Germany) (PCO) and the CO assessed by intermittent thermodilution (ICO).

Methods

With ethics committee approval, CO was assessed after cardiac surgery. For one set of data (dataset A) aFCO and for one set (dataset B) bFCO was used. After PiCCO calibration the mean of triplicate FCO, PCO and ICO values were recorded 15 minutes after inducing CO changes by different body positions (supine, 30° head-up, 30° head-down, supine). Statistical analysis was performed using the t test, ANOVA and Bland–Altman analysis for absolute values and percentage changes (Δ). P < 0.05 was considered significant.

Results

Data were obtained from 25 patients and 22 patients for dataset A and dataset B, respectively. Significant changes of FCO, PCO and ICO between measurement points were observed in datasets A and B. During dataset A, ΔaFCO was significantly greater and ΔPCO was significantly smaller than ΔICO induced by head-down positioning (P = 0.017 and P < 0.001, respectively). During dataset B no significant difference was observed between ΔbFCO and ΔICO. ΔPCO was significantly smaller than ΔICO during dataset B. Increased limits of agreement for aFCO-ICO and ΔaFCO-ΔICO (dataset A) were found when compared with PCO-ICO (Table 1). For dataset B the mean bias and limits of agreement were comparable.

Table 1 Bland–Altman analysis of absolute cardiac output (CO) values and percentage CO changes (Δ)

Conclusion

These results indicate that the new FloTrac software version (reduced time window for vascular compliance adjustment) improved performance of CO measurement in patients after cardiac surgery.