Pulse contour analysis after normothermic cardiopulmonary bypass in cardiac surgery patients

Monitoring of the cardiac output by continuous arterial pulse contour (CO PiCCOpulse ) analysis is a clinically validated procedure proved to be an alternative to the pulmonary artery catheter thermodilution cardiac output (CO PACtherm ) in cardiac surgical patients. There is ongoing debate, however, of whether the CO PiCCOpulse is accurate after profound hemodynamic changes. The aim of this study was therefore to compare the CO PiCCOpulse after cardiopulmonary bypass (CPB) with a simultaneous measurement of the CO PACtherm . Methods After ethical approval and written informed consent, data of 45 patients were analyzed during this prospective study. During coronary artery bypass graft surgery, the aortic transpulmonary thermodilution cardiac output (CO PiCCOtherm ) and the CO PACtherm were determined in all patients. Prior to surgery, the CO PiCCOpulse was calibrated by triple transpulmonary thermodilution measurement of the CO PiCCOtherm . After termination of CPB, the CO PiCCOpulse was documented. Both CO PACtherm and CO PiCCOtherm were also simultaneously determined and documented. Results Regression analysis between CO PACtherm and CO PiCCOtherm prior to CPB showed a correlation coefficient of 0.95 ( P < 0.001), and after CPB showed a correlation coefficient of 0.82 ( P < 0.001). Bland-Altman analysis showed a mean bias and limits of agreement of 0.0 l/minute and -1.4 to +1.4 l/minute prior to CPB and of 0.3 l/minute and -1.9 to +2.5 l/minute after CPB, respectively. Regression analysis of CO PiCCOpulse versus CO PiCCOtherm and of CO PiCCOpulse versus CO PACtherm after CPB showed a correlation coefficient of 0.67 ( P < 0.001) and 0.63 ( P < 0.001), respectively. Bland-Altman analysis showed a mean bias and limits of agreement of -1.1 l/minute and -1.9 to +4.1 l/minute versus -1.4 l/minute and -4.8 to +2.0 l/minute, respectively. Conclusion We observed an excellent correlation of CO PiCCOtherm and CO PACtherm measurement prior to CPB. Pulse contour analysis did not yield reliable results with acceptable accuracy and limits of agreement under difficult conditions after weaning from CPB in cardiac surgical patients. The pulse contour analysis thus should be re-calibrated as soon as possible, to prevent false therapeutic consequences.