Assessment of portable continuous wave Doppler ultrasound (ultrasonic cardiac output monitor) for cardiac output measurements in neonates

Abstract

Background and study purpose: The ultrasonic cardiac output monitoring (USCOM, USCOM Pty Ltd, Coffs Harbour, NSW, Australia) device provides a new method of non-invasively assessing cardiac output (CO). It has been successfully used in adults, but there have been few studies in neonates. Aims: To study the inter-operator reliability, and to compare the aortic (systemic) CO and pulmonary CO in a neonatal population. Patient and methods: In a study using the USCOM device, we have determined: (i) the inter-operator (rater) agreement for aortic (left ventricular output) and pulmonary (right ventricular output) CO; and (ii) by combining the measurements of aortic and pulmonary CO from each operator to obtain average aortic and pulmonary CO in neonates admitted to the neonatal unit during the first 8 days of life. Neonates with congenital heart disease were excluded from the study. Results: Twelve neonates were enrolled in the study, and their mean gestational age was 34.1 ± 3.7 weeks, mean birth weight 2.268 ± 0.872 kg with eight boys and four girls. There was no significant difference in CO measurements between the two operators (inter-rater correlation = 0.93 (0.86-0.97 (95% CI), P < 0.0001). However, the mean aortic CO was significantly lower than the mean pulmonary CO (228 mL/kg/min (202-254 (95% CI)) versus 282 mL/kg/min (256-309 (95% CI), P = 0.006). Conclusions: Although there was a good correlation between operators, further investigations are required to study the discrepancy between aortic (systemic)/pulmonary CO in this population. Other than this discrepancy, the validity of this technique in neonates requires further detailed studies as it uses continuous wave Doppler for the measurements.