Image Acquisition Method for the Sonographic Assessment of the Inferior Vena Cava

Summary

Point-of-care ultrasound evaluation of the inferior vena cava (IVC) is commonly utilized to identify, among other things, the volume status. Imaging should be performed systematically to ensure repeatability. This manuscript reviews the methods and pitfalls of sonographic IVC examination.

Abstract

Over the past several decades, clinicians have incorporated several applications of diagnostic point-of-care ultrasound (POCUS) into medical decision-making. Among the applications of POCUS, imaging the inferior vena cava (IVC) is practiced by a wide variety of specialties, such as nephrology, emergency medicine, internal medicine, critical care, anesthesiology, pulmonology, and cardiology. Although each specialty uses IVC data in slightly different ways, most medical specialties, at minimum, attempt to use IVC data to make predictions about intravascular volume status. While the relationship between IVC sonographic data and intravascular volume status is complex and highly context-dependent, all clinicians should collect the sonographic data in standardized ways to ensure repeatability. This paper describes standardized IVC image acquisition including patient positioning, transducer selection, probe placement, image optimization, and the pitfalls and limitations of IVC sonographic imaging. This paper also describes the commonly performed anterior IVC long-axis view and three other views of the IVC that can each provide helpful diagnostic information when the anterior long-axis view is difficult to obtain or interpret.

Introduction

Over the last several decades, the accessibility of point-of-care ultrasound (POCUS) has increased dramatically. Providers across medical disciplines can now integrate POCUS into their bedside exams and more readily identify important contributors to patients' conditions¹. For example, in acute care settings, one of the most important areas of focus is the assessment and management of volume status². Inadequate fluid resuscitation can result in tissue hypoperfusion, end-organ dysfunction, and severe acid-base abnormalities. However, overzealous fluid administration is associated with worsened mortality

Protocol

All procedures performed in the studies involving human participants were conducted in accordance with the ethical standards of the Duke University Health System Institutional Research Committee and with the 1964 Declaration of Helsinki and its later amendments or comparable ethical standards. The protocol was performed using input from several peer-reviewed papers in the academic literature^2,13,14,15. Imaging was performed on the authors themselves for the normal images and as part of routine educational ultrasound scans done for teaching p....

Results

Adequate exam
There is no single caliber or respirophasic behavior of the IVC that can be considered universally normal in all circumstances. For instance, the IVC seen in Videos 1-4 and Figure 3 was imaged in a healthy, hydrated male experiencing no acute illness. However, notably, this patient's "normal" IVC has a relatively large AP diameter, >2 cm in the ANT IVC LAX view, and shows minimal respiroph.......

Discussion

Even when properly imaged, information garnered from the IVC should not be the sole data point used for guiding treatment. The exact same IVC size and respirophasic changes can be seen in both normal states and in pathologic conditions. Therefore, the clinical context is critically important for guiding how to interpret the IVC data. Further, when using ultrasound to assess a patient's intravascular volume status, the published literature is mixed as to what thresholds of IVC size and respirophasic change accurately .......

Materials

Name	Company	Catalog Number	Comments
Edge 1 ultrasound machine	SonoSite	n/a	Used to obtain all adequate and inadequate images/clips