Drawing blood from central lines

[Altra]

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?

[brainkandy87]

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?

[BelgianRN]

No not once or twice but if you draw blood every 4 - 6 hours (which is about the standard for nearly all my ICU patients) and do this for 10+ days or even longer. And the patients have increased breakdown of their RBC's due to the critical illness and on top of that generally have decreased manufacturing for the same reason it can become a significant waste if you discard it every time. The effects are still noticeable even if you limit the amount of waste to 5 ml or even less.

But I'm going to try out MegNeoNurse's way of first giving 5 ml of NS to flush the line so hopefully I'll need less waste in that case.

[brainkandy87]

Ah, good point I guess. I'd still just be so hesitant to return a 20 ml syringe of blood into a pt, even if they were heparinized. I mean, at most I'm wasting 120 ml a day, but in reality you don't need to waste more than 10 ml for a central line, so you're wasting 60 ml/d at most. I'd take the loss over the risk of tossing clotted blood back into a pt. But then again, every situation/pt is different.