Estimation of cardiac output in a pharmacological trial using a simple method based on arterial blood pressure signal waveform: a comparison with pulmonary thermodilution and echocardiographic methods.
OBJECTIVE: Cardiac output (CO) has traditionally been measured using invasive techniques, which involve an element of risk. Thus, a reliable less-invasive method for determining CO would be very valuable for research use. We tested whether simple analysis of the arterial pulse waveform, not requiring large-vessel catheterisation or expensive equipment, could provide an estimate of CO that is accurate enough for pharmacological studies. METHODS: We measured CO in 11 healthy male subjects who received low and high doses of dexmedetomidine (alpha2-adrenoceptor agonist), using pulse contour analysis, echocardiography and pulmonary thermodilution techniques. RESULTS: At baseline, these methods gave the following mean (SD) values of CO: 6.18 (1.59), 5.22 (1.35) and 7.03 (1.54) l/min, respectively. High-dose dexmedetomidine reduced CO to 4.50 (0.68), 3.65 (0.65) and 4.80 (0.89) l/min, corresponding to -25 (14) %, -28 (12) % and -30 (14) % reductions from baseline, respectively. The pulse contour method described these dexmedetomidine-induced changes in CO very similarly to the thermodilution and echocardiographic methods. The limits of agreement [bias (2SD)] were 0.55 (2.55) and -0.10 (2.04) l/min, respectively. CONCLUSION: The minimally invasive pulse contour analysis technique might be suitable for pharmacological studies for the detection of major drug-induced reductions in CO.