No abstract

A pulse-contour-based method for continuous measurement of cardiac output (CO) and systemic vascular resistance (SVR) was tested and arterial thermodilution, used for calibration, was compared to pulmonary artery thermodilution. In 30 patients CO and SVR were measured by pulse contour analysis (COpc, SVRpc) 270 times in 24 h and compared to arterial (COart, SVRart) and pulmonary arterial (COpa, SVRpa) thermodilution measurements. The mean difference between COpa and COart was 0.26 L/min (3.6%) with a standard deviation (SD) of 0.7 L/min, the correlation coefficient was 0.96, and the coefficient of variation was 5.0% and 5.9% respectively. COpc did differ from COpa by 0.11 L/min (1.5%, SD = 0.6 L/min) and from COart by 0.15 L/min (2.1%, SD = 0.7 L/min). Correlation of COpc with COpa was 0.91, correlation of COpc with COart was 0.90. SVRpc did correlate with SVRpa, a coefficient of 0.94, and with SVRart, a coefficient of 0.92. Mean COpc and SVRpc did not differ significantly from COpa or COart and SVRpa or SVRart during the 24 h study period. It is concluded that COart correlates well with COpa and can be used to calibrate COpc. COpc and SVRpc agree with thermodilution-based CO and SVR without recalibration for 24 hours.

The continuous measurement of cardiac output (CO) appears to be a significant improvement in monitoring critically ill patients, espec~lly in cardiac surgery intensive care. Compared to common thermal dilution with a pulmonary artery cathether, computing of CO from the arterial pulse contour is less invasive and qualifies therefore as a routine method. Our device, (prototype, Pulsion Comp.) computes CO by analysis of the arterial pressure waveform (pulse contour, PC). For calibration of this system, a single arterial CO measurement by thermal dilution is necessary: 10ml iced saline solution are injected via central venous cathether and measured by the arterial PC cathether, that serves for pressure measurement too. Placing of a pulmonary artery cathether is not necessary.In 20 cardiac surgical patients CO was measured with pulmonary arterial and arterial thermal dilution 1, 2, 3, 4, 5, 6, 9, 12 and 24 hours postoperatively and compared to the corresponding CO derived from the PC method. Relative difference (precision) was +14.1% and +17.3% repectively. A significant difference between the variouos methods at the 24 hours point was not found. These results show, that the less invasive measurement of CO by pulse contour is a reliable, reproducible and continuously available alternative to pulmonary arterial thermal dilution.