Question about the anatomy & physiology of "breaking in" a new fistula

[fearless]

I've been doing hemo with a catheter for a couple months now.  I've run with one needle and the cath only four times.
Here's my question:  the nurses have explained that "best practice" is to run the needle as arterial and the cath as venous.  But they can't tell me why.  I'm guessing it's because if you infiltrate it shouldn't be as bad.  Also - probably better to be returning blood to the neck rather than be drawing it out there if something goes wrong.  But when the needle is run arterial, after about an hour it often alarms and begins to hurt here and there (nothing unbearable, but it would seem that the needle is probably pricking the inside of the vein.  One session a nurse (who's not there every time) switched the needle to venous, and it ran like a dream with no pain for the rest of the session.  But the regular nurses just want to pull and push and turn the needle around to fix the alarms.  I AM SO FREAKED OUT WHEN THEY DO THIS, because this is the way they gave me a horrendous infiltration (which was arterial by the way).  The infiltration happened almost 4 weeks ago, and my arm is still painful in a couple of areas. 
Also, I understand that running one needle in the arm will help to strengthen the vein, but wouldn't running it arterial only strengthen it distal to the needle?  (the side that the blood is coming from)  Whereas running it venous would help to strengthen it downstream: the direction the blood is flowing out of the needle and into the vein.

Can anyone explain to me how this really works?  I plan to ask my doctor to explain, but sometimes it takes a while to have such a conversation.   I would feel much better asking to alternate venous/arterial if i knew I was correct about how the direction of the blood flow strengthens the vein.  And if I'm all wrong about this, then I'll just keep my mouth shut!   I just really feel like the vein needs to get stronger before they put in the second needle, because so far it's been very difficult.  But how will running the needles as arterial strengthen the vein where the second needle needs to go?  The nurses are in a big hurry to get 2 needles in, but the doctor seems to be willing to let me call some of the shots.

Any advise? Thank you very much!

[Riki]

They did mine through alternating.  It started out, where they used the needle as the artery and the line as the vein.  They did this 3 times.  Then they switched it, and did that 3 times.  It was after that when they tried using 2 needles.  They weren't successful the first time, and it took a few months before they were able to consistently use 2 needles without the line.

Since your fistula is so new, I'm thinking that the reason you are feeling pain part way through treatment is that the fistula is getting tired. Changing the direction of the blood sometimes will help that, or stopping the treatment long enough to hook up to your catheter to give the fistula a rest.

Fistulas are tricky, and no 2 fistulas are the same.  Each one has to develop on it's own time.  There's one fellow in my unit who's had his fistula since August, I think, and they still are only getting one needle in.  I think they may have gotten 2 needles in a handful of times.

I will tell you, repositioning of the needle is something that will always be done.  I still cringe when they do it with me, because that is one of the easiest ways to be infiltrated.  After a while, you'll get to know the feelings, and whether or not a needle needs to be repositioned ("that feels like it's up against the wall, you might want to pull it back a smidge.").

[Restorer]

The reason that immediately comes to my mind is to avoid recirculation. Between the fistula and the catheter, it's just a straight line of veins. Taking blood from the fistula (arterial) and putting it back in the catheter (venous) will let the cleaned blood go all the way through your body again before it gets picked back up at the fistula.

[fearless]

thanks both.  I would be happy if the nurses would simply alternate the flow.  I think that would be a good way to build up the fistula.  I'm going to try to talk to the doctor to see if we can come up with a "plan of attack" so to speak    That way I won't have to defend myself to the nurses.  They can just do what the doctor orders!

[jojosmommy]

Here is a lesson I learned the hard way when I began with my fistula.  Yes, it is likely that your fistula will infiltrate easily at first.  It takes a good long while for that vessel to get strong.   It took a good 3 or 4 months before mine stopped infiltrating so easily.  I hope yours doesn't take that long!  However, the mistake I made was assuming the nurse knew what she was doing, I would sit there with my mouth shut and let her turn the needles, or push and pull and turn again.  The more she jacked with it, the higher the chance she would infiltrate it....and she did... many times.  Then she would try to stick me again higher up on my arm and infiltrate that!   Now, there is a certain amount of repositioning that will need to be done, but if you feel like they are doing too much then make them stop.  I would have rather signed off and not finished my treatment than let her jack with that needle and infiltrate my arm.  I'm too nice, and was too stupid to speak up for myself.   They more they use your fistula, the better you will be able to feel it and recognize what it SHOULD feel like.  If they are jacking with it too much, don't let them continue.  Speak up for yourself and tell them to leave it alone!

[fearless]

jojosmommy,  a million thanks. 
I will take courage from your advice the next time I have to tell one of them to STOP ALREADY!!!