To compare the accuracy and trending ability of the cardiac index (CI) measured by FloTrac/Vigileo™ (CIFT) or derived by the Fick equation (CIFick) using E-CAiOVX (enables continuous monitoring of oxygen consumption) with that measured by thermodilution (CITD) in patients with off-pump coronary artery bypass surgery. Twenty-two patients undergoing elective off-pump coronary artery bypass surgery were included. CIFT and CIFick were determined simultaneously at six time-points during off-pump coronary artery bypass surgery. At each time-point, phenylephrine (50 µg) was administered to increase systematic vascular resistance, with CI measured before and after administration (CITD used as reference method). Agreement of each method was evaluated by Bland-Altman analysis, while trending ability was evaluated by four-quadrant plot analysis and polar plot analysis. By Bland-Altman analysis, CIFT and CIFick showed percentage errors of 49.5% and 78.6%, respectively, compared with CITD. Subgroup analysis showed a percentage error between COFT and COTD of 28.9% in patients with a CI ≥ 2.4 L/min/m2, and 78.1% in patients with a CI ≥ 2.4 L/min/m2. The concordance rate of four-quadrant plot analysis was 93.3% for CIFT and 66.7% for CIFick in datasets where CITD ≥ 2.4 L/min/m2 before and after phenylephrine administration were included. CIFT and CIFick had wide limits of agreement with CITD, and were below acceptable limits for tracking phenylephrine-induced CI changes. However, subgroup analysis showed improved accuracy and trending ability of CIFT when only points where CITD ≥ 2.4 L/min/m2 were included, while there was no improvement in CIFick accuracy or trending ability.
Keywords: Blood pressure monitor; Cardiac output; Fick principle; Thermodilution.