Subcostal inferior vena cava view
From Echocardiography in ICU
How to get the inferior vena cava (IVC):
From the subcostal 4 chamber view, you will direct your probe medially to get the right atrium on the right of the screen and see a large part of the liver. Then you will rotate the probe 90° counterclockwise, till you see the long axis of the IVC through the liver and merging into the RA.
+++ It is very important to visualize the merging of the IVC with the RA: since the IVC is parallel to the abdominal aorta and has almost the same diameter and appearance, it can be very difficult to distinguish one from the other. To see the merging with the RA is the only way to be 100% sure that you are looking at the IVC and that you are not looking at the aorta.
Measurement of IVC diameter and respiratory variations
The measurement of the IVC diameter and its respiratory variation is the cornerstone of the evaluation of the patient's volume status.
You will measure the IVC diameter 2 to 3 cm before its merging in the RA, at the interface with the blood.
To assess the respiratory variations, you will measure and compare the smallest and the largest IVC diameter. One easy way to determine the extreme diameters is to use Mmode imaging. On the same image you will see the evolution of the IVC diameter with the respiration.