Comparison of cardiac output assessed by pulse-contour analysis and thermodilution in patients undergoing minimally invasive direct coronary artery bypass grafting

Objective: To investigate the precision and accuracy of continuous pulse contour cardiac output (PCCO) compared with intermittent transcardiopulmonary (TCPCO) and pulmonary artery thermodilution (TDCO) measurements in patients undergoing minimally invasive coronary bypass surgery (MIDCAB). Design: Prospective, controlled, clinical study. Setting: University hospital. Participants: Twelve patients undergoing MIDCAB. Interventions: Thirty-six measurements of PCCO and thermodilution cardiac output (CO) were simultaneously performed after the start of surgery, during bypass grafting, and at the end of surgery. TCPCO and TDCO were simultaneously assessed by three injections of ice-cold saline randomly spread over the respiratory cycle. The pulse contour device was initially calibrated with an additional set of aortic thermodilution measurements. Measurements and Main Results: Absolute values of CO ranged between 1.6 and 9.2 L/min. A close agreement among the three techniques was observed at all measurements. Mean bias between PCCO and TDCO and TCPCO was 0.003 L/min (2 SD of differences between methods = 1.26 L/min) and 0.27 L/min (2 SD of differences between methods = 1.16 L/min), respectively. The correlation coefficients were r(2) = 0.90 for TCPCO versus PCCO and r(2) = 0.88 for TDCO versus PCCO. Conclusion: The results of the present study show that compared with thermodilution CO, pulse contour analysis enables accurate measurement of continuous CO in patients undergoing MIDCAB. Copyright (C) 1999 by W.B. Saunders Company.