Zaven Sargsyan
Zaven Sargsyan

@sargsyanz

5 Tweets 1 reads Jan 17, 2023
Many medicine procedures involve (1) pushing a needle into a fluid-filled space, (2) advancing a plastic catheter over the needle into the space, (3) pulling the needle out, and (4) leaving the catheter in either for drainage or infusion.
Things often go wrong at (2).
1/5
When you first get a β€œflash” (enter the fluid filled space with your needle), only the very tip/distal part of the needle/bevel is in the target space.
Let’s use paracentesis as an example.
In these photos, the paper is the peritoneum, with views from both sides of it.
2/
If you try to advance the catheter now, it will hit up against the peritoneum and you will feel resistance. The extra force you exert might even make the needle come out of the peritoneum completely, and you might end up advancing the catheter into subcutaneous tissue.
3/
What you need to do instead is to advance the *needle* (with the catheter) a little bit more after you get the flash, until the entire bevel and catheter tip are in the desired space. It’s usually just a few more millimeters, like this.
4/
Now when you hold the needle still and push the white plastic catheter over it, the catheter will go in with minimal resistance, and you can proceed to steps 3 and 4.
Same principle applies to IVs, art lines, central lines, thoras, etc.
5/5

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