Comparison of Uncalibrated Arterial Pressure Waveform Analysis with Continuous Thermodilution Cardiac Output Measurements in Patients Undergoing Elective Off-Pump Coronary Artery Bypass Surgery

Objective Monitoring of cardiac output is required during anesthesia for off-pump coronary artery bypass (OPCAB) surgery. Recently, FloTrac, a new device for arterial pressure waveform analysis for cardiac output (APCO) monitoring without external calibration, was developed. The authors have compared APCO with STAT-mode continuous cardiac output (SCCO) in patients undergoing OPCAB surgery. Design A clinical study. Setting A university hospital (single institution). Participants Thirty consecutive patients undergoing elective OPCAB surgery. Interventions Arterial pressure measurement with FloTrac, pulmonary arterial catheter insertion. Measurements and Main Results APCO and SCCO measurements were recorded after pulmonary artery catheter insertion (T1), after sternotomy (T2), after heart positioning for left anterior descending artery anastomosis (T3, T4), after heart positioning for obtuse marginal artery anastomosis (T5, T6), after heart positioning for posterior descending artery anastomosis (T7, T8), and after sternal closure (T9). APCO and SCCO were compared using the Bland-Altman method and the percentage error by Critchley's criteria. SCCO and APCO ranged from 2.1 to 6.9 L/min and 1.2 to 7.4 L/min, respectively, and showed low correlation (r = 0.29). The overall bias by the Bland-Altman method between SCCO and APCO was −0.23 L/min, with a precision of −1.4 to 0.9 L/min, and the overall limits of agreement were −2.5 to 2.0 L/min. The overall mean CO was 4.0 ± 0.95 L/min. The overall percentage error between SCCO and APCO measurements was 57%. Conclusions Uncalibrated APCO values do not agree with thermodilution SCCO and significantly overestimated the SCCO in patients undergoing OPCAB surgery. Further evaluation is required to verify the clinical acceptance of FloTrac APCO in OPCAB surgery.