lab draws through central lines

SouthernLPN2RN, MSN, RN, APRN, NP · Nov 24, 2005

I can't find a policy on central line lab draws at my facility, but nurses have told me you need to first flush with 10 ccs of ns and then waste 10 ccs. Just wondering if anyone knows the rationale behind this. Thanks:)

Number one, they do need a policy. In regards to discarding the sample, this is done to avoid an over-diluted specimen from the flush and I've also heard it has something to do with bacteria that may be on the tip of the catheter. Good luck and hopefully somebody who knows more than me will be around, lol!!

Larry77, RN · Nov 24, 2005

We flush with 10cc NS then discard first 10cc aspirated, also we often use what's called a Leuer lock (sp?) its something usually used by lab that screws right on the positive pressure cap (or screws to a needle used by lab) it has a needle inside it covered with rubber for the vacutainers and you just pop each one that you need into it, they fill with the needed amount of blood per prefilled vacuum then you just unscrew and flush again with NS or Heparin depending on central line type.

Hope this helps a little :)

morrisonrn · Nov 24, 2005

Thanks for the responses, but I am wondering why you flush with 10ccs of ns first.

suebird3 · Nov 24, 2005

to make sure the line is patent.....clots can be a royal pain in the keister. (lol)

suebird

Gail-Anne · Nov 24, 2005

You have to flush first if it is a Groshong valve line (eg some PICCs) to activate the valve. Open-end central lines don't need a flush to work, if we have to take blood from a Hemodialysis line we never flush as they can have a high dose of Heparin in the line and you don't want to give that to the pt.

We withdraw 6 cc for discard for most blood tests, if drawing off a baby or frequently drawing off someone with low Hgb, you may want to reinsert their discard blood. As was already said, you need a policy to follow for your institution.

Larry77, RN · Nov 25, 2005

We are not allowed to mess with hemodialysis CL's I think the dialysis nurses and techs would have our heads...he he. Being that I work on a surgical/oncology floor we do use implanted chestports fairly often (usually for chemo or very long term abo's) and with those we usually just use same technique as one I mentioned earlier unless otherwise ordered by the doc.

Margaret51 · Nov 27, 2005

Another reason to flush the line first is to clean it out a bit. You don't want the blood you draw (even after drawing the discard blood) to have an undue concentration of anything you have been giving the patient. If you have the patient on a heparin gtt and don't flush and discard properly, your PTT will come back artificially high. This can cause you to miscalculate the gtt rate if you are using a heparin protocol.

NYNewGrad · Dec 7, 2005

we dont draw blood from central lines in my hospital. only docs can.

LISAMAR · Dec 7, 2005

when you're drawing for a blood culture do you still discard the waste? or do you use the waste for the blood culture

Larry77, RN · Dec 8, 2005

when you're drawing for a blood culture do you still discard the waste? or do you use the waste for the blood culture

When we do cultures we draw one out of the central and another sample out of a peripheral vein (requires two locations).

As far as I know we always discard first 10ml's but possibly not as necessary with cultures unless it is a heparin line...hmmm. Suppose it would be a question for a vascular doc.

One problem would be to change from the "always" discarding to only when you are not drawing cultures--this could create some confusion and we would have nurses forgetting. Personally I would rather everyone discards first 10ml's everytime unless ordered otherwise :)

hjmcenti · Dec 9, 2005

By wasting the first 10 cc you ensure that it is clean venous blood c no contamination from the outside port. Also, it is very important to clean the port c betadine and let dry a full 60 sec before taking a sample when drawing blood cx.