The aim of our study was to determine the validity of cardiac output (CO) measurements taken with the ultrasonic cardiac output monitor (USCOM) by comparing to CO measured by pulmonary arterial catheter (PAC) thermodilution during cardiac catheterization. We enrolled thirty-one children (<18 years) undergoing cardiac catheterization in this double-blinded, prospective, observational study. The median CO measured by USCOM was 4.37 L/min (IQR 3.73, 5.60 L/min) compared to 4.28 L/min (IQR 3.52, 5.26 L/min) by PAC thermodilution. The bias (mean difference) between the two methods was 0.2 L/min, and the 95% limits of agreement were -1.2 to 1.6 L/min. The mean percentage error of CO between USCOM and PAC thermodilution was 11%. When excluding a sole outlier, the bias between the two measures decreased to 0.1 L/min (95% limits of agreement -0.6 to 0.9 L/min), and the percentage error was reduced to 8%. The median SVRI measured by USCOM was 22.0 Wood Units (IQR 17.0, 26.8 Wood Units) compared to 22.1 Wood Units (IQR 17.6, 27.4 Wood Units) by PAC thermodilution. Bias (mean difference) between the two methods was -0.6 Wood Units, and the 95% limits of agreement were -8.2 to 6.9 Wood Units. We found that the estimation of CO and by extension SVRI with USCOM is reliable against pulmonary artery catheter thermodilution in children with normal cardiac anatomy. Given the noninvasive nature of USCOM, speed of measurement, and relative ease of use, it may be useful as a bedside tool for pediatric patients.
Keywords: Cardiac catheterization; Cardiac output; Child; Pediatrics; Thermodilution; Ultrasonics.