The subcostal view of the inferior vena cava (IVC) is used to assess IVC diameter and respirophasic variation to gauge “volume status.” However, in my clinical practice, I find this technique fairly useless outside of the extremes. For example, an IVC diameter of 28 mm makes me less inclined to give volume and more concerned about right-heart dysfunction, hypervolemia leading to venous congestion, etc.
I obtain this view by palpating the xiphoid process, moving just inferior to it, and aiming my ultrasound probe straight down to the spine with the probe indicator facing the patient’s head.
The superior and inferior vena cavas are “right-sided” structures, whereas the thoracoabdominal aorta is a “left-sided” structure. Because the IVC and aorta both run longitudinally in this view, it’s important to distinguish one structure from the other. Panning the ultrasound beam rightward will reveal the IVC with the hepatic vein(s) draining into it as well as the IVC-right atrium (RA) junction. Panning the ultrasound beam leftward will reveal the thicker-walled aorta, which runs alongside the spine and does not show respiratory variation. Remember, pulsatility alone is unreliable (think about patients on mechanical circulatory support, severe tricuspid regurgitation, etc.)!
In this video, I pan back and forth between the IVC and descending aorta on my Butterfly iQ+ to show the subtle but important differences between these structures. I often use point-of-care ultrasound (POCUS) as a cardiothoracic anesthesiologist and intensivist in my OR and ICU practices.
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