Central Venous Pressure Estimation by Ultrasound Measurement of Inferior Vena Cava and Aorta Diameters in Pediatric Critical Patients: An Observational Study

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Abstract
Objectives: To evaluate the ability to predict central venous pressure by ultrasound measured inferior vena cava and aortic diameters in a PICU population and to assess interoperator concordance. Design: Noninterventional observational study. Setting: PICU of a tertiary-care academic center. Patients: Eighty-eight pediatric patients (0–16 yr old) with a central venous catheter in place were studied. Sixty-nine percent of the patients received positive-pressure ventilation. Interventions: None. Measurements and Main Results: An experienced and a nonexperienced operator used ultrasound to measure the maximal diameter of inferior vena cava and minimal diameter of the inferior vena cava and the maximum diameter of the abdominal aorta from the subxiphoid window. The inferior vena cava collapsibility index and the ratio of maximal diameter of inferior vena cava/maximum diameter of the abdominal aorta were then derived. The central venous pressure was measured using a central venous catheter and recorded. Twenty-three patients had low central venous pressure values (≤ 4 mm Hg), 35 patients a value in the range of 5–9 mm Hg, and 30 patients high values (≥ 10 mm Hg). Both inferior vena cava collapsibility index and ratio of maximal diameter of inferior vena cava/maximum diameter of the abdominal aorta were predictive of high (≥ 10 mm Hg) or low (≤ 4 mm Hg) central venous pressure. The test accuracy showed the best results in predicting low central venous pressure with an inferior vena cava collapsibility index greater than or equal to 35% and ratio of maximal diameter of inferior vena cava/maximum diameter of the abdominal aorta less than or equal to 0.8, and in predicting high central venous pressure with an inferior vena cava collapsibility index less than or equal to 20% and ratio of maximal diameter of inferior vena cava/maximum diameter of the abdominal aorta greater than or equal to 1.3. Inferior vena cava collapsibility index returned generally higher accuracy values than ratio of maximal diameter of inferior vena cava/maximum diameter of the abdominal aorta. Lin’s coefficient of concordance between the operators was 0.78 for inferior vena cava collapsibility index and 0.86 for ratio of maximal diameter of inferior vena cava/maximum diameter of the abdominal aorta. Conclusions: Inferior vena cava collapsibility index and ratio of maximal diameter of inferior vena cava/maximum diameter of the abdominal aorta correlate well with central venous pressure measurements in this PICU population, and specific inferior vena cava collapsibility index or ratio of maximal diameter of inferior vena cava/maximum diameter of the abdominal aorta thresholds appear to be able to differentiate children with high or low central venous pressure. However, the actual clinical application of these statistically significant results remains limited, especially by the intrinsic flaws of the procedure.

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