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Lean Left – IVC Compression in Pregnancy

May 1, 2019

Written by Clay Smith

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A 30° left tilt in late pregnancy was most effective in reducing uterine compression of the IVC in this MRI study. However, nearly a quarter of women achieved the greatest IVC volume with a 30° right tilt.

Why does this matter?
When late third trimester pregnant patients are placed supine, they may become hypotensive, with compression of the IVC by the gravid uterus, impaired venous return, and decreased cardiac output. The usual solution is to tilt the patient 15° to the left in order to move the uterus off the IVC, which runs to the right of the midline. However, some studies have suggested a right tilt or a 30° left tilt may be better. So, which is it?

No puns on the advantage of leaning left based on this study…
This was a clever MRI study in 13 pregnant women between 31-39 weeks gestation. They were tilted 15° or 30° to the left or right; IVC and aortic volumes were calculated. There was no significant change in aortic volume with any position. A 30° left tilt was the best position on average, with the biggest reduction of gravid uterine compression of the IVC compared to supine and right 30° tilt. A 15° left tilt was not statistically better than supine. In all, 70% (9/13) had the greatest IVC volume in the 30° left tilt position. Oddly enough, 23% (3/13) had the greatest IVC volume in the 30° right lateral tilt position. This has immediate clinical implications. If a third trimester pregnant patient comes in supine, tilt her 30° to the left; 15° is likely not enough. If she remains unstable (hypotensive), try tilting her 30° to the right. Tilt to the left. Tilt to the right. Stand up. Sit down…well you get the idea.


Supine. IVC compressed (white arrow outline). Solid arrow, aorta. Modified from cited article.

Supine. IVC compressed (white arrow outline). Solid arrow, aorta. Modified from cited article.


Zoomed in on compressed IVC while supine. Gee, it’s smushed. Modified from original

Zoomed in on compressed IVC while supine. Gee, it’s smushed. Modified from original


30° left tilt, larger IVC. Solid arrow, aorta. Modified from cited article.

30° left tilt, larger IVC. Solid arrow, aorta. Modified from cited article.


Zoomed in on larger IVC, 30° left tilt. Modified from cited article.

Zoomed in on larger IVC, 30° left tilt. Modified from cited article.

Source
Effect of Right-Lateral Versus Left-Lateral Tilt Position on Compression of the Inferior Vena Cava in Pregnant Women Determined by Magnetic Resonance Imaging. Anesth Analg. 2019 Apr 3. doi: 10.1213/ANE.0000000000004166. [Epub ahead of print]

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