Triple Lumen Cath anatomy

[NurseCollins799]

So I have a question...

I'm pausing Lido and heparin gtts to draw lido and ptt levels off of a tlc. Lumen 3 is clotted off. I d/c'd heparin gtt because it had best blood return. Our policy says pause gtts for 3 minutes, flush whichever lumen, waste 10cc then draw.

I did this and I got outrageously high lido & ptt levels.

I went and redrew, only this time paused both for 10 minutes and got normal readings.

Can someone explain tlc's as they relate to this situation? I thought they were essentially 3 separate lumens housed in a singular line. In other words, why would a 3 minute pause lead to high levels but a 10 minute pause be normal? Shouldn't the flush clear the lines...the waste clear the saline, and the 3 minutes circulate adequate blood so the blood at the tip is no longer concentrated with medication?

This is me confused...

[aCRNAhopeful]

They are separate lumens each with their own size. The brown port is typically the largest and best for volume

[MunoRN, RN]

Preferably a lumen is left for draws that doesn't have something infusing through it that would alter the result. Even with flushing it can be difficult to get a sample for a ptt out of a lumen that was infusing heparin that isn't at all altered by residual heparin in the lumen. As I remember, lidocaine and heparin are compatible, so I would combine the two and save a lumen for draws/fluids.

You shouldn't have to stop the infusion for more than a few minutes, the flow of blood in the SVC is typically around a liter/minute, plenty to flush away what's infused recently.

Ideally you should TPA the third lumen, but if you're going to use the same lumen to draw labs, a "stop/start" flushing technique will flush the line more effectively than a continuous flush due to the physics of fluid flow in a tube. After it's flushed and you've waited a few minutes, you don't need to waste 10cc, that's potentially harmful, the recommended waste volume is 2-3 times the lumen volume, which is typically around 1cc.

[sweetdreame, BSN, RN]

I don't understand the rationale of flushing before drawing the waste???

[delphine22]

Thanks, I was just about to ask this. Our policy is to get peripheral sticks for all blue tops if the pt has heparin in the central line, but sometimes that's literally impossible. (Though I did have a wonderful phleb who spent 20 minutes compressing third-spaced fluid out of a site so she could get a good stick.)

Does this same procedure work if there's TPN going through the line? Hold a few minutes, flush, waste?

[IVRUS, BSN, RN]

Delphine,

A lumen dedicated to TPN, needs to be just that, dedicated to TPN. Therefore, you really do NOT want to draw labs from that lumen. Instead, do a peripheral stick, or draw from another lumen. But, always remember to stop all infusions for a full minute before drawing from the other lumen.

There is one study that suggests that if you must draw coags from a lumen and you only have that single lumen IV catheter, accurate results may not be seen unless you aspirate 20-25 CC of discard. After which a 20 cc NS flush is in order. Now, if this is done often enough, your pt is at great risk for too much blood loss and subsequent anemia. However, this is said to produce the best results.

[MunoRN, RN]

I don't understand the rationale of flushing before drawing the waste???

It's generally thought that at least 20cc of fluid (of some sort) must flush through the line to adequately remove enough heparin to produce a ptt that isn't significantly altered. There really isn't any reason why that fluid needs to be the patient's own blood, saline will in theory do the job better and is far less harmful.

If it's an infusion that shouldn't be flushed in (pressors for instance), then that fluid should be withdrawn, line flushed, then waste to access undiluted blood. Otherwise, clear the heparin from the line with saline (using 20cc or more), then waste 2-3 times the lumen volume (usually 5cc or less).