Pulse contour analysis versus thermodilution in cardiac surgery patients

BACKGROUND: Previous studies have demonstrated that there is a lack of agreement between intermittent cold bolus thermodilution (ICO) and a semicontinuous method with dilution of heat (CCO) in cardiac surgical patients following hypothermic extracorporeal circulation (HCPB). Therefore, the aim of the present study was to compare both ICO and CCO with continuous pulse contour analysis (PCCO): a method based on a fundamentally different principle of determining cardiac output (CO). METHODS: A prospective criterion standard study of 25 cardiac surgery patients undergoing HCPB. Cardiac output was determined using the three methods (ICO, CCO, and PCCO) before and after HCPB up to 12 h after arrival on the ICU. Bias and precision were evaluated. RESULTS: A total of 380 triple determinations of CO could be analyzed. During the entire study period bias PCCO-ICO was -0.14 l*/min (precision 1.16 l*/min) and bias CCO-ICO was -0.40 l*/min (precision 1.25 l*/min). Up to 45 min after bypass PCCO agreed with ICO (bias -0.21 l*/min, precision 1.37 l*/min), while bias CCO-ICO was -1.30 l*/min (precision 1.45 l*/min). CONCLUSION: The agreement between PCCO and ICO in contrast to CCO in the first 45 min after HCPB indicates that CCO underestimates CO during this period.