85 - Sizing Up the IVC: A Prospective POCUS Study of Diameter and Collapsibility in Healthy Pediatric Populations

Publication Number: 2081.85

Abigail McKenzie, University of South Carolina School of Medicine Columbia, Columbia, SC, United States; Hannah L. Green, University of South Carolina School of Medicine Columbia, Lexington, SC, United States; Kevin Weinberger, Prisma Children's Hospital/ University of SOuth Carolina, Columbia, SC, United States; Duncan L. Norton, University of South Carolina School of Medicine Columbia, Columbia, South Carolina, SC, United States; Kristopher Dixon, Prisma Children's Hospital - Midlands, Columbia, SC, United States; Jeffrey Holloway, University of South Carolina School of Medicine Columbia, Columbia, SC, United States; Abigail McKenzie, University of South Carolina School of Medicine Columbia, Columbia, SC, United States

Background: Point of care ultrasound (POCUS) is a noninvasive, low-cost, and painless approach used across pediatrics in emergency and critical care evaluations. The diameter of the inferior vena cava (IVC) and its respiratory variation have been explored as indicators for evaluating hypovolemia, predicting fluid responsiveness, and evaluating the risk of fluid overload, with limited reference values for pediatric IVC diameters and collapsibility index (CI) in healthy patients.

Objective: This study aims to establish normative reference values for IVC diameters and CIs in healthy pediatric patients aged 0 to 18 years using POCUS.

Design/Methods: We performed a prospective observational study of 135 healthy patients between the ages of 0 and 18 years who presented to PRISMA Children’s Hospital Outpatient Clinic for well-child visits. Patients with any chronic or acute illness were excluded. Ultrasound measurements of the IVC were performed according to American Society of Echocardiography recommendations by utilizing curvilinear 1.4-5.7-megahertz probe. We obtained time-lapsed imaging of the IVC for at least three tidal breaths approximately 2 cm away from the inferior cavoatrial junction. Using M-mode on the GE Venue Go 4 ultrasound machine, three maximum and minimum diameters were manually measured and used to calculate the IVC CI.

Results: In this preliminary study of 135 healthy pediatric patients, IVC maximum diameter demonstrated a positive correlation with age, increasing across age groups ( < 6 months to 13–18 years), with an R² value of 0.53. IVC minimum diameter showed a similar trend (R² = 0.496). In contrast, CI values remained stable across age groups (R² = 0.017). BMI had limited predictive value for IVC dimensions or CI (all R² < 0.12).

Conclusion(s): These early findings suggest that age, rather than BMI, is a more reliable predictor of normative IVC size in healthy pediatric patients. The consistency of CI values across age groups aligns with adult data, supporting CI ranges of 20–50% as normative regardless of age. These results reinforce the utility of POCUS-derived IVC measurements as a tool for assessing volume status in children across emergency and critical care settings. However, as this is an early study conducted in healthy patients, the findings may not fully extrapolate to acutely ill populations. Additionally, this study focuses solely on the CI, which applies only to spontaneously breathing patients not receiving positive-pressure ventilation. These findings, therefore, provide valuable baseline data for comparison in patients without respiratory distress or support requirements.