Drawing blood through a Saline Lock??

Nurses General Nursing

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I recently started a new job - which I LOOOVE, and am so much happier at, but the other day, I had a pt who was upset that the lab was coming to "stick her" when a nurse on another floor drew her blood through her saline lock, and told her she wouldn't have to be stuck anymore because we could just draw blood that way. The woman came in with bilateral PE's and needed a PT/INR drawn, plus and CBC and CMP. I've never heard of drawing blood through a saline lock before and couldn't get blood return anyway through any of them (she had 2) even though they flushed fine. Am I off track here - I don't think it's a good idea to do this. :no:

Specializes in ICU.

No, not a great idea to do this, but yes it can be done. But most of the time I find it doesn't work. If the s/l is fairly new and hasn't had anything running in it , sometimes you will get blood return back using a tourniquet. But if there is difficulty in getting blood back then the results may be scewed too. You also have to take a waste, which ( if you get that much ) is all you get!

Sometimes if we are desperate, we try this .. usually if there are no central lines, and if the pt is a hard poke. But I also work in peds so this is a little more understandable than in adults who in general are easier to get bloodwork on.

I recently started a new job - which I LOOOVE, and am so much happier at, but the other day, I had a pt who was upset that the lab was coming to "stick her" when a nurse on another floor drew her blood through her saline lock, and told her she wouldn't have to be stuck anymore because we could just draw blood that way. The woman came in with bilateral PE's and needed a PT/INR drawn, plus and CBC and CMP. I've never heard of drawing blood through a saline lock before and couldn't get blood return anyway through any of them (she had 2) even though they flushed fine. Am I off track here - I don't think it's a good idea to do this. :no:

It's not a good idea to do. I've also experienced the same problem you do since it seems to be common practice (or so the patients tell me) to draw blood from SLs in ICU and ER. The only time I will draw blood from a peripheral IV site is when I initiate a new site and the patient will be due in the next few hours for labs. I DO NOT draw labs from established sites for the same reasons Weekend Warrior posted:

No, not a great idea to do this, but yes it can be done. But most of the time I find it doesn't work. If the s/l is fairly new and hasn't had anything running in it , sometimes you will get blood return back using a tourniquet. But if there is difficulty in getting blood back then the results may be scewed too. You also have to take a waste, which ( if you get that much ) is all you get!

If I have a patient on a heparin gtt, I will try to draw blood from the opposite arm that the heparin is infusing in to ensure accurate results.

You may obtain blood specimens from the site when inserting a med lock, before attaching the lock end or j-loop, usually easily and without fear of contamination, but once the med lock has been used, most physicians do not consider this site a prime site for blood specimens. Usually a medport

or dual port groshong catheter is used for giving med and one tip maintained for blood specimens.

Specializes in Oncology/Haemetology/HIV.

It is not a good idea to draw blood specimens through a saline lock unless it is when the lock is placed.

For one thing, it can cause you to lose the site, and they will get stuck again anyway.

There is also an issue with drawing coag labs. Some lab personnel/MDs will tell you that as soon as you start the saline lock, within minutes some natural coagulation changes take place due to the "injury", and drawing coag labs from the site (after it has been in) will corrupt the results and render them inaccurate. If you note how often lines clot off after a time, this makes sense.

The other issue is i this patient is getting IV anticoagulants through the lock (as they have DVTs/PEs), your results will be corrupted by the very presence of the anticoagulant. Because no matter how well you flush and waste, most locks will still potentially have some drug/saline, especially if there are any extra ports on it.

I will do it for pts who are hard sticks or frightened of needles. You have to have at least a 20-g in or the cells will hemolyze. You can also draw from a running line....turn the IV off, waste 5 mls of blood, and draw what you need.

In the ER, we almost exclusively draw our labs off the IV. Obviously when it's just started, and then for repeat labs like cardiac markers, or tests the MD decides to add on later. ;)

Well, where I work the CCU and Telemetry Unit Nurses all draw their own blood-through PICC, Central line, saline locks, and sticks.

You must have a 'waste" so the blood won't be diluted by the saline .

Specializes in primary care, pediatrics, OB/GYN, NICU.
It is not a good idea to draw blood specimens through a saline lock unless it is when the lock is placed.

For one thing, it can cause you to lose the site, and they will get stuck again anyway.

There is also an issue with drawing coag labs. Some lab personnel/MDs will tell you that as soon as you start the saline lock, within minutes some natural coagulation changes take place due to the "injury", and drawing coag labs from the site (after it has been in) will corrupt the results and render them inaccurate. If you note how often lines clot off after a time, this makes sense.

The other issue is i this patient is getting IV anticoagulants through the lock (as they have DVTs/PEs), your results will be corrupted by the very presence of the anticoagulant. Because no matter how well you flush, most locks will still potentially have some drug/saline, especially if there are any extra ports on it.

This is a very important point! In terms of accurate PT/INR's I definitely have to agree with this one. Our coumadin clinic won't even use the same finger stick on a patient if the first doesn't give a sample due to inaccurate INR readings.

Specializes in Neuro, Acute, Geriatrics, Rehab, Oncology.

In our ED some do draw blood off a just initiated IV before the J loop or adapter is placed. I do not ,as frequently the blood sample will hemolyze and the patient will be re stuck. I also adhere to the mantra that I will not risk an IV site for the sake of a blood draw. There are many more sites suitable for a venipuncture vs IV start on most folks.

I think risk of hemolysis depends a lot on the size of catheter and vein. I very rarely get hemolysis with #20 or larger, in an AC or forearm...vs more common hemolysis with a #22 in a hand. And I've never lost an IV site from drawing blood off of it. We use a positive pressure flushing technique, which probably helps.

Specializes in LDRP.

For non central lines, plain ol heplocks/saline locks, etc I've been told that when you first start the line, and the tourniquet is still in place you can, but after that, no can do.

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