Ultrasonographic measurements of the inferior vena cava diameter in newborns: is it a useful tool for choosing an umbilical venous catheter?

Objectives: The primary outcomes of this study were to evaluate the diameters of the inferior vena cava (IVC) in a cohort of newborns and the correlation between newborn weight and IVC diameter. The secondary outcome was to evaluate the concordance between the measurements performed by the two investigators.

Methods: Two blind examiners performed an ultrasonographic (US) evaluation of the IVC diameter in neonates with a weight ranging from 2 to 4 kg. The exclusion criteria included hemodynamic instability, known vascular malformations, and major congenital malformations.

Results: A total of 143 neonates were enrolled between June 2019 and January 2021. All the US examinations were performed in the first 3 days of life. After dividing the patients into two groups according to their weight at the time of examination (2.0-2.99 kg and 3.0-4.0 kg), the median IVC diameters measured by examiner 1 were 3.1 mm (interquartile range 2.8-3.4) and 3.4 mm (interquartile range 2.9-3.8) ( = 0.003) for the two groups, respectively. The median IVC diameters measured by examiner 2 were 3.1 mm (interquartile range 2.6-3.3) and 3.3 mm (interquartile range 2.8-3.8) ( = 0.004) for the two groups, respectively. The intraclass correlation coefficient was 0.93 (95% CI: 0.90-0.95).

Conclusion: The IVC diameter values varied widely from 1.2 to 5.2 mm in newborns weighing 2-4 kg, and a low correlation between newborn weight and IVC diameter was found, so measuring IVC diameter may be a recommended step prior to inserting a umbilical venous catheter (UVC). The concordance between operators was good. We contemplated that the IVC diameter could be a potentially useful tool to identify the most appropriate UVC, thus reducing the risk of catheter-related thrombosis.