Background: Cardiac function, including cardiac index (CI), traditionally has been measured by a pulmonary artery catheter (PAC). A noninvasive alternative for measuring cardiac function would offer obvious advantages.
Methods: A prospective study of trauma and nontrauma patients was performed in a surgical intensive care unit over a 3-month period. CI was determined using both a standard PAC and a continuous-wave Doppler ultrasound (UTS). The study had 2 phases: phase I was nonblinded and phase II was blinded; the correlation between UTS- and PAC-derived CI was assessed.
Results: A total of 120 paired measurements of CI were observed in 31 patients. The UTS-derived CI measurements showed agreement with PAC measurements in both phase I and phase II of the study with a bias of .06 L/min/m(2) +/- .4 L/min/m(2). Paired measurements correlated well in both phase I (r = .97, R2 = .95, P < .0001) and phase II (r = .93, R2 = .86, P < .0001) of the study.
Conclusions: Doppler UTS correlates well with PAC measurements of CI. This noninvasive modality is an accurate and safe alternative to PAC.