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.