Continuous pulse contour analysis after cardiopulmonary bypass in cardiac surgery

Introduction

Continous pulse contour analysis is an alternative to the pulmonary artery catheter for continous cardiac index (CI) measurement after cardiac surgery. However, it remains to be determined whether pulse contour analysis has to be re-calibrated after cardiopulmonary bypass (CPB). The aim of the study was to compare continous pulse contour CI analysis after CPB and a period of initial stabilisation with a simultaneous transpulmonary thermodilution measurement of CI.

Method

After ethical approval and written informed consent 50 patients were included into this prospective study. During aortocoronary bypass surgery, CI was determined by a PiCCO monitor (Pulsion Medical AG, Munich, Germany) in all patients. Prior to surgery the continous pulse contour analysis was calibrated by triple transpulmonary thermodilution measurement of CI. In case of a deviation >10% of a measurement, five measurements were performed and the highest and lowest were rejected. After termination of CPB and initial stabilisation of the patient (20 ± 2 min) continuous pulse contour CI was documented. Simultaneously, the PiCCO monitor was re-calibrated by transpulmonary thermodilution measurement and this CI was documented as well. Statistical analysis was performed by the method described by Bland and Altman.

Results

After termination of CPB and initial stabilisation of the patient, continous pulse contour analysis determined a CI of 3.1 ± 0.9 l/min/m². After re-calibration, a CI of 3.6 ± 0.7 l/min/m² was measured (P < 0.01). The mean bias between continous pulse contour analysis CI and transpulmonary thermodilution measurement of CI after CPB was -0.5 l/min/m². Precision (2SD) was 1.5 l/min/m².

Conclusion

Due to the broad distribution and the underestimation of the CI after CPB, a re-calibration of the continous pulse contour analysis is essential after weaning from CPB to prevent false therapeutic consequences.