Comparison of a Non-Invasive with Two Minimally Invasive Cardiac Output Monitors During Off-Pump Coronary Artery Bypass Surgery

Title Comparison of a non-invasive with two minimally invasive cardiac output monitors during off-pump coronary artery bypass surgery. Background Cardiac index (CI) can be measured using arterial pressure curve analysis, which can be derived either minimally invasive from the radial artery (e.g. FloTrac/Vigileo™ (CIFTV) or ProAQT-Pulsioflex™ (CIPA)) or completely non-invasively with a finger cuff (e.g. ccNexfin™ (CINF)). Assuming that CIFTV and CIPA are clinically interchangeable, we compared CIFTV and CIPA with each other and the average of the minimal invasive CIFTV and CIPA (CIAVR) with non-invasive CINF. Methods In 70 patients undergoing off-pump coronary artery bypass surgery, CI was compared at predefined events during anesthesia (before and after induction of anesthesia, before and after sternotomy). Values were compared by Bland-Altman analysis for repeated measures. Four-quadrant plots and polar plot methodology were used to evaluate CI trending ability. Results Agreement analysis of CIFTV versus CIPA showed a bias of -0.2 l min-1 m-2, limits of agreement (LOA) of ± 1.5 l min-1 m-2 and percentage error (PE) of 103% (fig A). CINF slightly underestimated CI compared to CIAVR with a bias of 0.6 l min-1 m-2, LOA of ± 1.6 l min-1 m-2 (p<0.001), PE of 102% (fig. B). Polar plot analysis revealed moderate concordance to track CI changes comparing CIFTV to CIPA and CIAVR to CINF (83% and 90% within 30o limits of agreement) (fig. C, D). Conclusions The arterial pressure curve derived CIFTV and CIPA reveal a similar agreement and trending ability with each other as with noninvasive CINF. Therefore, noninvasive CINF can be considered as interchangeable with the minimal invasive arterial pressure curve based CI monitors.