IV draw vs Lab draw?

[Double-Helix]

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?

[murphyle, BSN, RN]

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.

[turnforthenurse, MSN, NP]

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...

Because you're not uncapping and recapping the ports...

I was taught (when drawing blood from an IV) to take the port OFF so that all you have is the cannula, then connect your blood drawing stuff to that and draw your tubes. Once you're done with that, recap the heplock port.

You don't do that with central/A-lines.

[hiddencatRN, BSN, RN]

I thought the issue was the fibrin sheath that grows over the catheter as it stays in the vessel. We draw off IVs in the ED all the time.

[GM2RN]

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.

I was a phleb before becoming a nurse, and I agree with this post. The only thing I would add is that I agree with the other poster who said, basically, that there is no more risk for infection drawing from PIVs than central lines, as long as proper technique is used. The risk for contamination comes from having run meds through the PIV at some point prior to going back and drawing blood.