Bioreactance and fourth-generation pulse contour methods in monitoring cardiac index during off-pump coronary artery bypass surgery

Validation of cardiac output estimation using the fourth-generation FloTrac/EV1000™ system in patients undergoing robotic-assisted off-pump coronary artery bypass surgery

The pulmonary artery catheter (PAC)-despite its invasiveness-remains the gold standard for cardiac output (CO) monitoring. The FloTrac system, a less invasive hemodynamic monitor has been developed, which estimates CO using arterial pressure waveform analysis without external calibration. Recently, an upgraded version of FloTrac system with improved algorithm to follow changes in vascular resistance was introduced into the market. The aim of this study was to assess the reliability of the CO estimated from the fourth-generation FloTrac/EV1000 system (CO_FT) compared to that measured with PAC using the thermodilution method (CO_PAC) during robotic-assisted off-pump coronary artery bypass (OPCAB) surgery. CO_FT and CO_PAC were obtained simultaneously at 4 predefined time points during robotic-assisted OPCAB: 5 min after the induction of general anesthesia (T1), after starting one-lung ventilation (T2), after capnothorax (T3), and after mini-thoracotomy was performed (T4). The agreement of data was investigated by Bland-Altman analysis. Thirty-four patients were initially enrolled. After exclusion, 32 patients and a total of 128 paired CO measurements were obtained. The overall bias was 1.46 L/min, the 95% limits of agreements were - 3.40 to 6.33 L/min, and the percentage error was 72.98%. Regression analysis of the systemic vascular resistance index (SVRI) and the bias between CO_PAC and CO_FT showed that the bias was moderately correlated with the SVRI (r² = 0.43; p < 0.0001). Despite a software upgrade, the reliability of the fourth-generation FloTrac/EV1000™ system during robotic-assisted OPCAB to estimate CO was not acceptable, especially in patients with low SVRI.

Comparison between Fourth-Generation FloTrac/Vigileo System and Continuous Thermodilution Technique for Cardiac Output Estimation after Time Adjustment during Off-Pump Coronary Artery Bypass Graft Surgery: A Retrospective Cohort Study

(1) Background: Previous studies reported limited performance of arterial pressure waveform-based cardiac output (CO) estimation (FloTrac/Vigileo system; CO-FloTrac) compared with the intermittent thermodilution technique (CO_int). However, errors due to bolus maneuver and intermittent measurements of CO_int could limit its use as a reference. The continuous thermodilution technique (CO_cont) may relieve such limitations. (2) Methods: The performance of CO-FloTrac was retrospectively assessed using continuous recordings of intraoperative physiological data acquired from patients who underwent off-pump coronary artery bypass graft (OPCAB) surgery with CO monitoring using both CO-FloTrac and CO_cont. Optimal time adjustments between the two measurements were determined based on R-squared values. (3) Results: A total of 134.2 h of data from 30 patients was included in the final analysis. The mean bias was -0.94 (95% CI, -1.35 to -0.52) L/min and the limits of agreements were -3.64 (95% CI, -4.44 to -3.08) L/min and 1.77 (95% CI, 1.21 to 2.57) L/min. The percentage error was 66.1% (95% CI, 52.4 to 85.8%). Depending on the time scale and the size of the exclusion zone, concordance rates ranged from 61.0% to 75.0%. (4) Conclusion: Despite the time adjustments, CO-FloTrac showed non-negligible overestimation, clinically unacceptable precision, and poor trending ability during OPCAB surgery.

Reliability of Bioreactance and Pulse-Power Analysis in Measuring Cardiac Index in Patients Undergoing Cardiac Surgery With Cardiopulmonary Bypass

OBJECTIVES

Less-invasive and continuous cardiac output monitors recently have been developed to monitor patient hemodynamics. The aim of this study was to compare the accuracy, precision, and trending ability of noninvasive bioreactance-based Starling SV and miniinvasive pulse-power device LiDCOrapid to bolus thermodilution technique with a pulmonary artery catheter (TDCO) when measuring cardiac index in the setting of cardiac surgery with cardiopulmonary bypass (CPB).

DESIGN

A prospective method-comparison study.

SETTING

Oulu University Hospital, Finland.

PARTICIPANTS

Twenty patients undergoing cardiac surgery with CPB.

INTERVENTIONS

Cardiac index measurements were obtained simultaneously with TDCO intraoperatively and postoperatively, resulting in 498 measurements with Starling SV and 444 with LiDCOrapid.

MEASUREMENTS AND MAIN RESULTS

The authors used the Bland-Altman method to investigate the agreement between the devices and four-quadrant plots with error grids to assess the trending ability. The agreement between TDCO and Starling SV was qualified with a bias of 0.43 L/min/m² (95% confidence interval [CI], 0.37-0.50), wide limits of agreement (LOA, -1.07 to 1.94 L/min/m²), and a percentage error (PE) of 66.3%. The agreement between TDCO and LiDCOrapid was qualified, with a bias of 0.22 L/min/m² (95% CI 0.16-0.27), wide LOA (-0.93 to 1.43), and a PE of 53.2%. With both devices, trending ability was insufficient.

CONCLUSION

The reliability of bioreactance-based Starling SV and pulse-power analyzer LiDCOrapid was not interchangeable with TDCO, thus limiting their usefulness in cardiac surgery with CPB.