IVC Assessment

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Probe(s): Curvilinear or Phased array 

Preset: Abdominal or cardiac

1. Start with a subxiphoid cardiac view to visualize the heart
2. Identify the IVC as it enters the right atrium and center it on the screen
3. Slide side-to-side to locate the IVC at its largest intrahepatic diameter
4. Once centered, rotate the probe clockwise (indicator toward the feet) to obtain a longitudinal view of the IVC entering the right atrium

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.

Dry: Max diameter < 1 cm or collapses > 50% with inspiration.

Indeterminate: Max diameter > 1 cm and collapses 5–50%.

Full: Max diameter > 1 cm and collapses < 5%.

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 alongside other clinical parameters.