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 Ϯ 3.7 weeks, mean birth weight 2.268 Ϯ 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.

Non-invasive cardiac output monitoring in neonates

“…Of note, a difference in LVO and RVO was also seen when assessed by conventional echocardiography. This is in line with the results of our study using the USCOM technique in neonates (LVO: 228.3 (95% CI 202.1 to 254.5) ml/kg/min) vs RVO 282.3 (95% CI 256.0 to 308.5) ml/kg/min; p =0.006) 2. Of interest, this imbalance was not substantially modulated by the presence of a persistent ductus arteriosus in our cohort.…”

“…There may also be a systemic error in the calculation of the cross-sectional area of aortic and pulmonary values (from the Nidorf equations4), and as the weight of the baby increases, the error increases as well, as demonstrated in our study 2. The Nidorf equations for these neonates are also based on a small number of measurements, and this is also a limitation of the method.…”

Measurement of systemic oxygen delivery and inotropy in healthy term neonates with the Ultrasonic Cardiac Output Monitor (USCOM)

“…The USCOM is a relatively new continuous-wave Doppler (CWD) device for measuring hemodynamics noninvasively at the bedside, which appears to be both accurate and reproducible [20][21][22][23][24]. The USCOM calculates DO 2 from the standard formula (see Subjects and methods), and the Smith-Madigan method calculates the SmithMadigan inotropy (SMI) value and inotropy index (SMII) [25].…”

Monitoring the Neonate: Basic Science

“…The authors concluded that echo-based measures and USCOM measures were not interchangeable. As in the term infants, the USCOM-measured RV output was signifi cantly greater than the LV output in a group of preterm infants suggesting the device systematically overestimates RV output [ 17 ]. In a subsequent publication, Meyer et al suggested that the USCOM device undergo further controlled clinical trials before its wide application in the neonatal ICU [ 18 ].…”