Inferior Vena Cava Ultrasound for Assessing Volume Status and Fluid Responsiveness in Critically ill Patients: A Systematic Review

Abstract

Background: The assessment of intravascular volume and fluid responsiveness is challenging in the management of critically ill patients. Diagnostic methods of hemodynamic monitoring must be safe, reproducible, and practical. Objective: To describe the applicability of ultrasound indices of the inferior vena cava in the assessment of intravascular volume and prediction of fluid responsiveness in critically ill patients. Method: A systematic review performed of the PubMed®, Latin American and Caribbean Health Sciences Literature, and Scientific Electronic Library Online databases for articles published in the previous five years. The descriptors used were “inferior vena cava,” “ultrasonography,” “fluid responsiveness,” and “volume status.” Results: The search identified 13 relevant articles. The collapsibility index of the inferior vena cava was 25%–50% as the cutoff point for defining hypovolemia and showed applicability in predicting fluid responsiveness in patients breathing spontaneously with cutoff points of 25%–57%. In mechanical ventilation scenarios, the distensibility index of the inferior vena cava was more effective at predicting fluid responsiveness than the other measurements with variation of 10.2%–20.5%. The inferior vena cava/aorta diameter index was especially useful in the pediatric population for defining intravascular volume; however, in adults, there were many divergences in its applicability. Conclusion: The assessment of intravascular volume and fluid responsiveness through ultrasound indices of the inferior vena cava is applicable and safe for diagnosing and monitoring hemodynamic instability. However, studies of value standardization are necessary due to divergences in the cutoff points used in each index.