Accuracy of beat-to-beat cardiac output monitoring by pulse contour analysis in hemodynamical unstable patients.

BACKGROUND: Continuous determination of cardiac output (CO) by transpulmonary thermodilution calibrated pulse-contour analysis is gaining clinicical acceptance. However there is doubt, whether this method is reliable in hemodynamic instable patients. We compared pulse-contour analysis to thermodilution in patients with profound changes of CO.

MATERIAL AND METHODS: 24 patients were investigated. CO was measured by thransthoracic thermodilution and pulse-contour analysis in intervals of 60 min during study periods of 8-44 h without recalibration of the pulse-contour computer. Results of 517 measurements were compared by regression, structural regression and Bland-Altman analyses.

RESULTS: Mean change of CO was 40 +/- 27% (range 20-139%), range of systemic vascular resistance was 450 dyn x s/cm(-5) - 2360 dyn x s/cm(-5). Correlation of pulse-contour analysis CO to thermodilution CO was r=0.88 with p=0.0001, bias was 0.2 l/min with 1.2 l/min standard deviation. Mean CO by pulse-contour analysis did not differ significantly from CO by thermodilution during the study period. There were no influences of heart rate or arterial pressure on the difference between both methods.

CONCLUSIONS: CO measurement by arterial pulse-contour analysis is reliable even in patients with profound changes of CO or during hemodynamic instability.