IV draw vs Lab draw?

  1. What is the rationale for drawing labs directly from the vein rather than from the IV or saline lock?
    When I did clinicals, most patients in the hospital had labs drawn at least once a day. Policy was to have the lab come up and draw the sample from a vein, of course meaning that the patient had to get poked each and every day. The only exception was if a patient had a central line that had been approved for draws (like a port-a-cath) then the nurse could do it.

    I've never understood why we can't take a sample from the IV in the left AC, but can use a new stick in the right AC to draw one. Is this policy at your facility? What is the rationale?
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  2. 15 Comments

  3. by   Turd Ferguson
    Not really sure of the rationale for it, I imagine it has something to do with maintaining the patency of the IV cannula or ensuring the accuracy of labs (not mixed with flush/administered fluids).

    The ER of one facility I rotated through would draw their labs through a fresh IV stick (before flush). After the line was flushed, a lab stick had to be done to obtain any more specimens.
  4. by   roma4204
    you can ruin an IV by drawing blood back from it, especially if the patient is on antibiotics. also, when it comes from an IV it doesn't always get the return you want and the lab can reject it because it can clot (if any comes out at all)

    i would rather poke someone very shortly in a good vein than risk losing an IV and having to take the time to poke them again and redraw the labs
  5. by   classicdame
    there is too much risk of losing the IV site if blood is drawn through it. Central lines are different of course. Also, you have a higher risk of coagulation and would have to re-start the IV.
  6. by   LegzRN
    My hospital says it's an infection control issue. They have also eliminated all phlebotomists from the staff. Blood draws is now entirely a nursing task.
  7. by   Rob72
    Interesting perspectives! The actual rational is avoiding contamination of the specimen, and/or hemolysis. this goes waaaay back to when steel butterflies were the IV catheter.

    Yes, you can cause vessicular trauma that will blow the site; you can also lyse the blood (more easily) when drawing through the IV cath. Vessicular trauma is also the reason we really should not be doing AC sites unless absolutely necessary.
  8. by   ShortStackRN
    Drawing blood from an exsisting IV site is not done for several reasons...the two main reasons being that this poses a huge risk for infection and also when you draw back from the IV site you are more than likely going to lose the site causing the patient even more pain by starting more IVs.

    Our facility doesn't have phlebotomists either...only nurses and specially trained PCAs are allowed to draw labs. And we are also not ever allowed to take blood from an IV site unless it's a new IV start.
  9. by   akulahawkRN
    Quote from Rob72
    Interesting perspectives! The actual rational is avoiding contamination of the specimen, and/or hemolysis. this goes waaaay back to when steel butterflies were the IV catheter.

    Yes, you can cause vessicular trauma that will blow the site; you can also lyse the blood (more easily) when drawing through the IV cath. Vessicular trauma is also the reason we really should not be doing AC sites unless absolutely necessary.
    From my understanding, you use a fresh stick because of the contamination issue. Some lab equipment/tests are sensitive enough that if anything other than NS has been run through the line, it'll pick that up, and even then, you can get a bad read if you draw and don't discard that first draw, and some tests are sensitive enough that even trace ABX or heparin in the cath can still be detected even if you do draw & discard and then go for a sample. At least, that's the rationale I was given years ago. All of this is for either a locked-off IV or a cath that's been d/c from the running line temporarily to allow a sample to be taken.
  10. by   turnforthenurse
    Not 100% sure on the rationale, but I would think it would be an infection risk...you would have to screw off the port to get to the cannula and then you have an open source for bacteria and germs to get into the patient's body.

    If I have to put in a brand new IV and the patient also has some labs that need to be ordered, I will insert the cannula, plug it off for a moment so that the patient is bleeding everywhere while I connect the other supplies to draw my tubes, then heplock and flush. That way the patient doesn't get stuck twice. That is the ONLY time I will ever do that, though. Otherwise the patient will have to get stuck with a butterfly or if they have a central line or A-line, then that will get used.
  11. by   Rob72
    Quote from melosaurRN
    ...or if they have a central line or A-line, then that will get used.
    So what I have to pitch back to you is, how is the A line/central/port different in infection risk than accessing the PVA site? Unless all your central access kits are antibiotic impregnated...
  12. by   mama_d
    Honestly, I think it's b/c the samples (especially green tops) are more likely to hemolyze and then the facility has to pay for another test to be run.

    I have to admit, if I've got a pt with an access with brisk blood return, I'll do it that way...and explain that it's technically against policy, so the pt shouldn't expect that anyone else would do it that way. It's one of the reasons why, especially if I'm working three or four shifts in a row, if I'm starting an IV I shoot for a juicy vein. (As long as it's not in the AC unless they need it for testing protocols...can't stand the AC accesses and neither can the pts usually.)

    ETA...

    The equipment we use, you don't have to unscrew the hub, the needleless system locks right into it, so it stays a fairly closed system.

    And we do have silver-impregnated caps for our central lines/PICCs/PACs to help eliminate line infections. They're fairly new, so I'm not sure what, if any, the decrease in numbers for those are yet.
  13. by   Frozen08
    As a former Lab Tech... It varies on the hospital. Ours uses IV's for labs sometimes.
    T
    Infectious contamination is less of an issue than ruining the access with a clot, but the biggest issue is contamination of the sample (mixing normal saline and other pharms in with blood sample is common, as was hemolysis).

    This can all be avoided by doing said collection following the right protocol.
    We too switched phlebotomy to nursing to save money, only to switch back to having phlebotomists a few years later due to poor sample quality and increased value errors.

    I'm glad we don't do blood draws, it can be a colossal time suck.
  14. by   murphyle
    We go back and draw off PIV locks occasionally in the EC, based on a few criteria: 1) the patient has poor vascular access and/or won't tolerate an additional stick (peds and geri, I'm looking at you); 2) nothing has been run through the line other than .9; and 3) you get brisk blood return from the line and can draw the sample with minimal manipulation of the site. Generally the call for additional draws will be within 30 minutes of starting the line, making thrombosis slightly less of an issue, and we love our 18-gauges in Emergency , so it's a little different than going back and drawing off a three-day-old 22ga PIV that was already on its last legs. Some things absolutely can't be drawn this way, for example blood cultures (must be a fresh venipuncture site unless you're culturing an existing central line), and you can't draw from a pre-hospital line (major risk of infection - EMS lines aren't known for their pristine conditions). And, of course, the floor will never do it this way, for all the reasons already mentioned.

    We scrub the hub with alcohol or ChloraPrep prior to re-draws, and waste 10 mL in adults and 3 in babies prior to drawing the actual sample. Syringe draws work a lot better than Vacutainer draws when you're working this way; you have control over how much suction you're applying to the line, and you can stop if you meet resistance or get line vibration. Hemolysis generally isn't any more of a problem drawing this way than it is from a butterfly puncture.* Once you have what you need, flush the line with 10 mL .9 and you're done.


    * Personally, I think a lot of the hullabaloo over hemolysis is bad lab technique. You don't know how many times I've had to draw and draw and re-draw on patients, a new venipuncture every time, because the lab swears the sample was hemolyzed; and then I'll call the lab phlebotomists to come do it themselves, and lo and behold their samples come up "hemolyzed" too. We've also noticed that the hemolysis monster tends to appear at odd intervals, and when it happens, literally everyone's samples will magically come up "hemolyzed" at the same time. One night you can send the Worst. Draw. EVER. down and it'll be fine, and the next night send a beautiful draw out of a juicy vein and they'll claim "hemolysis." Verrry eeenterestink. But not funny.

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