Echocardiographic assessment of blood flow volume in the SVC and descending aorta in the newborn infant

Abstract

Background:Clinical methods of assessing adequacy of the circulation are poor predictors of volume of blood flow in the newborn preterm. Doppler echocardiography can be used to assess perfusion at various sites in the circulation.

Objective:To assess repeatability of measurement of volume of superior vena caval (SVC) and descending aortic (DAo) flow.

Design:SVC and DAo flow volume were assessed four times in the first 48 hours of postnatal life in a cohort of preterm (<31 weeks) infants. Within and between observer repeatability was assessed in a subgroup of preterm infants. Normative values were derived from 14 preterm infants who required <48 hours respiratory support, and in 13 healthy term infants.

Results:Within-observer repeatability coefficient was 30 ml/kg/min for quantification of SVC flow, and 2.2 cm for DAo stroke distance. Measurement of DAo diameter had poor repeatability. Between-observer repeatability was significantly worse than within-observer. The 5th centile for volume of SVC flow in healthy preterm infants was 55 ml/kg/min. The 5th centile for DAo stroke distance was 4.5 cm.

Conclusions:Echocardiographic assessments of volume of SVC flow and velocity of DAo flow have similar within-observer repeatability to other neonatal haemodynamic measurements. Between-observer repeatability for both measurements was poor, reflecting the difficulty of standardising these novel techniques. In this small cohort of preterm infants, SVC flow volume <55 ml/kg/minute and DAo stroke distance <4.5 cm represent low or borderline systemic perfusion in the first 48 hours of postnatal life.