The inferior vena cava (IVC) can be assessed with POCUS to estimate intravascular volume status and right atrial pressure. IVC size and respiratory variation can help guide fluid management. A small, collapsing IVC may suggest low right atrial pressure and potential hypovolemia while a dilated, non-collapsing IVC may suggest elevated right atrial pressure, seen in conditions like fluid overload, right heart failure, or pulmonary hypertension.
While IVC assessment can be useful, it has its limitations. Factors like elevated intra-abdominal pressure (e.g., ascites), positive pressure ventilation (e.g., PEEP, NIV), right sided valve disease, and body habitus, among many other others can affect IVC measurements. Always interpret IVC findings alongside other parameters and the clinical context.
Probe(s): Curvilinear or Phased array
Preset: Abdominal or cardiac
View: Supxiphoid
Pitfalls: Mistaking IVC and aorta, not measuring IVC within intrahepatic portion, cutting the IVC at incorrect angle and not at max diameter, not accounting for ascites, not accounting for positive pressure ventilation.
Steps for Image Acquisition:
The video shown is an indeterminate IVC. The IVC is collapsing > 5% and is greater than 1cm in max diameter
In spontaneously breathing patients, ask them to sniff or take a deep breath. The IVC diameter is largest during expiration and smallest during inspiration. In ventilated patients, this pattern reverses due to positive pressure: the IVC is largest during inspiration and smallest during expiration.
Interpretation of RA pressure relative to IVC
💡 Tip: In mechanically ventilated patients, interpretation is more complex and IVC distention may occur without clear collapsibility.
💡 Tip #2: IVC scanning is a surrogate measure for right atrial pressure, and so we are making the assumption when looking at that the patient has a normal right atrial pressure at baseline