After several years working in the ER, I am relatively new to critical care. I have a question regarding drawing labs from central lines.
Several nurses I work with now like to draw labs in the following manner: attach a syringe at the stopcock port, draw 10-20mL for "waste", leave the syringe with the "waste" blood attached, close the port and draw off needed labs, then return the "wasted" blood to the patient. I understand that it's never actually left the line circuit. But maybe too many years of "hemolyzed samples" being the bane of my existence when dealing with the lab has made me wary of this practice.
What is the risk of hemolysis in the syringe and what is the risk of returning some hemolyzed blood to the patient's circulation? What is the comparative risk to the compromised, anemic patient of losing 10-20mL with each blood draw?
Jan 12, '10
I have never had hemolyzed labs when drawing from a line only when drawing from an INT or a stick.
Those 20ml of waste can quickly add up when you're doing q3 or q4 serial labs for 2-3 days. We use an edward's closed system and return the waste via it.
Jan 12, '10
It is usually acceptable as long as the waste has stayed in the closed system.
My experience is with Chemo/Heamatology/BMT pts often getting research drugs. These people are getting frequent blood draws, multiple tubes, and are not producing their own components for extended periods of time. Research labs can be 4-10 -10mL tubes, not counting waste. And, yes, the waste adds up.
You need to check withIV, that the closed system used is appropriate, though. The NIH had an "approved" closed system setup that was used, and demonstrated as safe.
Jan 13, '10
A saftey set, as described above, is best for this purpose.
Even though you are keeping the system "closed" as you describe it, it DOES increase the infectious risk every time to access the line.
The risk of returning this blood to the pt is only from an infectious standpoint.
Also you don't need to draw 10-20 cc before you draw your specimens, that's too much, esp if you're going to truly waste that blood.
If you have a normal ga. CVL and draw slowly the hemolysis risk is pretty low to zero.
Jan 13, '10
Thanks all, for the input.
Jan 15, '12
I disagree I don’t think there is any more risk in doing this, if you practice proper practice, for infection than there would be in simply giving an IV med through the CVL.
Jan 15, '12
Sometimes a 20cc draw (or more!) is required depending on what drips you have running. Ex: If you need coags but have a Heparin drip running. Even if you stop the drip, you can get a contaminated sample. It happens.
Jan 15, '12
Our base fluid is glucose not normal saline so we need a waste of about 10 - 20 ml if we want accurate glucose levels when drawing blood out of this lumen. Generally we'll use the art line or CVP-port that's run with NS and use a smaller waste.
@ OP: I can't imagine that giving the waste blood back will lead to clinical problems. It's only outside of the body for a short time. Theoretically you can have some clotting and/or hemolysis in the blood that's in stasis in your syringe. But that amount will be so little that the body will cope with this without problems.
Only time I get the lab call back with hemolysed samples is when there was too much force exerted when drawing the blood. Although nowadays they just won't even call and we have to magically smell they won't do the labs....
I think I recall someone telling me a few years back that with a 2 - 3 ml waste and blood 4 - 6 times a day it adds up to a unit of packed cells in a month time.
Jan 18, '12
I do not like this method of drawing labs. It is a greatly "Modified" mixing method.
In the mixing method, the clinician takes her syringe and withdraws 5-7 cc, and then IMMEDIATELY reinfuses it. He or she then withdraws again, and then IMMEDIATLY reinfuses the blood again. this is repeated approx. 4 times never detaching the syringe from the line. However, with this procedure, though the blood specimen has not been disconnected from the line via the stopcock, It still has been allowed to SIT TOO LONG and therefore clots have been formed and then the nurse is reinfusing these clots. So, no, this is not approriate.
If one is worried about the patient suffering from Iatrogenic anemia from too many phlebotomy specimens collected, the mixing method is best, but not this modification of it.
Feb 9, '12
I work in a PICU and regardless of age or weight, we return the waste when drawing from a CVC, with the acception of heme/onc patients. I found the practice of vigorously scrubbing the hub, instilling 3ml NS, withdrawing 5ml waste, drawing blood needed for lab, returning waste and then flushing with enough NS to clear the line. Never had an issue with contaminated specimen (even if TPN had been running) or hemolysis. As another poster mentioned, clotting is not generally an issue if it is venous and the line draws well. Now if there is heparin or another anti thrombotic running, I would not use that lumen to draw (for obvious reasons folks...)Hope this helps!
Feb 9, '12
Are you disconnecting the waste syringe from the line? If so, that us a very DANGEROUS practice. Also if you remain connected, but hesitate too long before returning the 5 mls of "waste" you run an enormous risk of the specimen clotting. This too should not be reinfused into a pt.
Feb 12, '12
Maybe my brain isn't working from working all day and night, but I'm not understanding the rationale behind returning the waste when drawing from a central line. To me, the risk far outweighs any possible reward. I mean, is that 10-20 ml of waste going to bottom out their h&h?
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