Cardiac index measurements by transcutaneous Doppler ultrasound and transthoracic echocardiography in adult and pediatric emergency patients.

INTRODUCTION: Non-invasive hemodynamic monitoring may facilitate resuscitation in critically ill patients. Validation studies examining a transcutaneous Doppler ultrasound technology, USCOM-1A, using pulmonary artery catheter as the reference standard showed varying results. In this study, we compared non-invasive cardiac index (CI) measurements by USCOM-1A with transthoracic echocardiography (TTE).

METHODS: This study was a prospective, observational cohort study at a university tertiary-care emergency department, enrolling a convenience sample of adult and pediatric patients. Paired measures of CI, stroke volume index (SVI), aortic outflow tract diameter (OTD), velocity time integral (VTI) were obtained using USCOM-1A and TTE. Pearson's correlation and Bland-Altman analyses were performed.

RESULTS: One-hundred and sixteen subjects were enrolled, with obtainable USCOM-1A CI measurements for 99 subjects (55 adults age 50 +/- 20 years and 44 children age 11 +/- 4 years) in the final analysis. Cardiac, gastrointestinal and infectious illnesses were the most common presenting diagnostic categories. The reference standard TTE measurements of CI, SVI, OTD, and VTI in all subjects were 3.08 +/- 1.18 L/min/m(2), 37.10 +/- 10.91 mL/m(2), 1.92 +/- 0.36 cm, and 20.36 +/- 4.53 cm, respectively. Intra-operator reliability of USCOM-1A CI measurements showed a correlation coefficient of r = 0.79, with 11 +/- 22% difference between repeated measures. The bias and limits of agreement of USCOM-1A compared to TTE CI were 0.58 (-1.48 to 2.63) L/min/m(2). The percent difference in CI measurements with USCOM-1A was 31 +/- 28% relative to TTE measurements.

CONCLUSIONS: The USCOM-1A hemodynamic monitoring technology showed poor correlation and agreement to standard transthoracic echocardiography measures of cardiac function. The utility of USCOM-1A in the management of critically ill patients remains to be determined.