If the pressures aren’t stable and almost always about the same, then the most likely scenario is that the tip of the needle is not in the centre of the vein. It’s touching or very close to the wall of the vein. In addition to altering the flow into the needle, it will also make your fistula spasm, plus every time you bend your arm a bit during the treatment, this tip of the needle will touch the wall even more, sending your pressure out of limits and triggering an alarm.
If your upper arm fistula is anything like mine, everything changes if your arm isn’t held exactly the same way each time you are putting a needle in. I have to make sure I alway hold my arm out straight, and my hand palm up. Otherwise, even if I can get the dull needle in, the angle won’t be the same.
Yes, getting the scabs off can be difficult. Sometimes there really isn’t a scab. Don’t dig for it. If there isn’t a scab on the surface, just break the entry point a bit with the tip of the syringe needle you are using. This will ensure the dull needle goes in at the right spot exactly. If you draw blood, sponge it off with a gauze so you can clearly see your entry point (I then use an alcohol swab just to ensure it’s clean).
It doesn’t sound like I’m using exactly the same procedure as some others on this forum. I’m not sure what Gus means. My needles are already connected to a 20ml syringe and already flushed before I put them in. Once a needle is in, I tape it, and then pull blood up and then push it back down, leaving a couple of ml of blood at the bottom of the syringe. Flushing this way will prevent clotting of one needle while you put the other one in, and until you start the treatment. By pulling up blood hard for the arterial and pushing it down hard for the venous, it also helps to ensure you’ve got it in right. I’ve never had a needle clot.
By the way, how you tape the needle down is also going to affect pressures. I use Tegaderms, not tape - because I do nocturnal hemo (so it has to be very secure). However, no matter what you use, you have to be sure you’re not taping down so tight that you are changing the angle of the needle. SOP for me is a 2x2 gauze folded over in half and stuffed under the needle before I tape it down. In fact, I started out with one gauze, but I soon realized I need two of them under each needle. Upper arm fistulas can be fussy like that, because the vein is deep.
And finally, fistulas can change over time. In my program, they have us come in about every 6 months or so to do a short daily treatment in-centre so they can do a Transonic on the fistula. As a matter of fact, I have to go in this morning, so I had better start getting ready