Point-of-Care Ultrasound Assessment of the Inferior Vena Cava in Mechanically Ventilated Critically Ill Children

Objectives The objective of this study was to compare the ultrasound-measured inferior vena cava distensibility index (IVCdi), inferior vena cava distensibility variability (IVCdv), and inferior vena cava-to-aorta ratio (IVC/Ao) to other common methods to assess fluid status in mechanically ventilated pediatric critically ill patients. These methods include central venous pressure (CVP), percent fluid overload by weight (%FOw), and percent fluid overload by volume (%FOv). Methods This was a prospective observational study of a convenience sample of 50 mechanically ventilated pediatric patients. Ultrasound measurements of the inferior vena cava and aorta were obtained, and the IVCdi, IVCdv, and IVC/Ao were calculated and compared to CVP, %FOw, and %FOv. Results The median %FOw was 5%, and the median %FOv was 10%. The mean CVP +/- SD was 8.6 +/- 4 mm Hg. The CVP had no significant correlation with %FOw or %FOv. There was no significant correlation of the IVCdi with CVP (r = -0.145; P = .325) or %FOv (r = 0.119; P = .420); however, the IVCdi had a significant correlation with %FOw (P = .012). There was also no significant relationship of the IVCdv with CVP (r = -0.135; P = .36) or %FOv (r = 0.128; P = .385); however, there was a significant correlation between the IVCdv and %FOw (P = .012). There was no relationship between the IVC/Ao and any other measures of fluid status. Conclusions In this cohort of mechanically ventilated pediatric intensive care unit patients, many commonly used markers of fluid status showed weak correlations with each other. The IVCdi and IVCdv significantly correlated with %FOw and may have potential as markers for fluid overload in this patient population.