4. Cardiac Ultrasound (Echo) Pathology

Central Venus pressure (CVP) estimation

Ultrasound of the Inferior Vena Cava (IVC) can be used to estimate the central venous pressure (CVP) of a patient by looking at the size (diameter) and collapsibility of the IVC. This is especially useful when you are trying to evaluate fluid tolerance or the presence of venous congestion in your patients.

Here is a simplified and practical table you can use to interpret your IVC findings.

IVC SizeIVC CollapsibilityInterpretation (CVP)
< 1.5cm>50% collapsibility0-5 mm Hg (Low CVP)
< 1.5-2.5cm>50% collapsibility6-10 mm Hg
1.5-2.5cm<50% collapsibility11-15 mm Hg
>2.5cm<50% collapsibility16-20 mm Hg (High CVP)

Adapted from Kircher et al.

The caveat about IVC measurements is that it just gives you a static measurement to estimate the central venous pressure. So all of the limitations of using CVP will also pertain to IVC measurements.

We find it most useful when the IVC either estimates a low CVP or high CVP. The measurements in between can be considered indeterminate and more advanced hemodynamics measurements should be obtained to assess for venous congestion and fluid responsiveness (change in cardiac output)

Collapsible IVC Long Axis cardiac ultrasound echocardiography
Small and Collapsible IVC
Dilated Non-Collapsible IVC Long axis cardiac ultrasound echocardiography
Dilated and Non-collapsible IVC and hepatic vein

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