So yesterday had a case that really brought out this issue. One of my ICU patients didn’t have a great urine output, so instead of playing a guessing game looking at urea, creatinine, ins & outs, etc, etc (hopefully no one is thinking CVP…), I did what any self-respecting bedside sonographer would and went for a direct look.
Here is what his IVC in standard long axis looked like:
So…it looks like its about 20mm, and not a whole lot of variation seen. Hmm, maybe he’s on the “fuller” side. Some may even consider that he wouldn’t be volume-responsive.
Before we go on, lets just have a brief physiological review. What we are looking for when assessing IVC is an idea of its volumetric change with respiratory swings. So ideally we should be obtaining a 3D volume measurement, but maybe the traditional 2 point diameter may suffice, assuming that the IVC is a near perfect cylinder. Assuming?
I’ve mentioned this in a previous IVC post (http://wp.me/p1avUV-8E).
So let’s get back to yesterday’s patient. Short axis:
Yes, the IVC is that tall, skinny sliver that collapses completely with (gentle) inspiration. Still think that this patient is in the full side? Maybe not. Gave him some fluid and the urine output picked up.
This is why I think much of the IVC literature is imperfect. Unfortunately the appealing idea of standardizing IVC assessment to a single two-point measurement is inherently flawed, due once again to individual patient variation. It would be great to see all those studies re-done with a global IVC assessment strategy. In the end, it isn’t any more time-consuming – just like the Simpson’s disks vs eyeballing.
Oh yeah, again, if you are an acute care doc, and you like the cutting edge, donate forget to register for CCUS 2015, Montreal, may 1-3! www.ccusinstitute.org!