Comparison of cardiac output in OPCAB: bolus thermodilution technique versus pulse contour analysis

The study was designed to evaluate the clinical agreement between intermittent bolus thermodilution technique and pulse contour analysis technique. Sixty patients with normal left ventricular function undergoing elective off-pump coronary bypass surgery were included in this prospective study. In addition to routine monitoring, a 7.5F pulmonary artery thermodilution catheter via right internal jugular vein and a 4F arterial thermodilution catheter into femoral artery were also placed. Cardiac output measurements were compared before induction, after induction, after sternotomy, during the various anastomoses, post-protamine and post-sternal closure. Statistical analysis was performed using analysis of agreement to assure bias distribution of differences between the two methods by using Bland and Altman analysis. The cardiac output values obtained at preinduction, post-induction, and post-sternal closure time points showed good agreement, whereas the values obtained during the various anastomoses showed significant differences (p <0.05). Therefore it was concluded that pulse contour analysis cannot be relied upon completely whenever there is a change in the position of heart or alteration in systemic vascular resistance. But the trends in cardiac output were in complete agreement during the entire procedure.