Comparison between a suprasternal or high parasternal approach and an abdominal approach for measuring superior vena cava Doppler velocity in neonates.

OBJECTIVES: Superior vena cava (SVC) flow is becoming an important hemodynamic measurement in neonates through its use in targeted neonatal echocardiography. Previous studies measured the flow velocity in the SVC through an abdominal approach. In adults and children, the abdominal and the suprasternal or high parasternal window are considered equivalent. We compared the two approaches in neonates. Our hypothesis was that the two echocardiographic approaches would yield similar results.
METHODS: We conducted a prospective observational study of 40 neonates with gestational ages of 23 to 40 weeks and weights of 540 to 3805 g. Interventions included measurements of SVC flow velocity from an abdominal approach and a suprasternal or high parasternal approach. The main outcome measure was the SVC velocity time integral.
RESULTS: The SVC velocity time integral was able to be measured from both approaches in all patients. The abdominal velocity time integral yielded on average slightly higher values by 5.1% (95% confidence interval, 0.6% to 9.8%). This finding was statistically significant for the whole sample (P = .025). The median of the absolute percent difference between measurements was 9.7% (range, 1.6% to 28.8%). The individual results were within the 95% confidence interval for intraobserver variability of the thoracic velocity time integral in 36 of 40 neonates. Times to completion were similar in both groups, with a slight advantage for the thoracic approach in larger neonates.
CONCLUSIONS: The suprasternal or high parasternal approach is feasible and an acceptable alternative to the abdominal approach for measuring SVC flow velocity in the context of targeted neonatal echocardiography. Angle correction is usually necessary.