Drawing labs from CVCs

There's a lot of flow going by the lumen openings of a central line which moves the fluids coming out of them downstream fairly quickly. Even so, particularly with openings that are close to each other, it's still important to stop the other fluids at least while the sample is being drawn. You don't necessarily need to wait long, stopping the other lumens for only 10 or 15 seconds allows those fluids to get far enough downstream that they aren't going to significantly contaminate your sample. Ideally you're using a vamp which makes for a quick draw-back of waste and lab draw, then restart the drips as soon as you've gotten the blood. If you're ready to go when you stop the drips then from stopping them to restarting should take 30 seconds or less.

Or, if you've got an A-line then you don't need to stop the drips at all.

This highly depends on the type of catheter.

Some catheters have a staggered lumen design where the openings are separated and are designed to allow for draws with fluids running. Arrow catheters are famous for this, if you look at some of the types of Arrow catheters they have distal and proximal openings. As long as you draw from the distal port you should have near zero issues with fluid reflux.

As always, #1 follow the manufacturer's instructions for that particular type of catheter. #2 consult your facility policy.

7 minutes ago, Wuzzie said:

I think we are saying the same thing but our facilities differed in which one was denoted proximal vs distal.

I think we are. Always a debate with catheters if you use anatomical distal or use the catheter distal.

Technically we weren’t supposed to draw off CVCs where I worked. Plus most of my patients who had all their access connected to pressors and sedation almost always had an A-line. The two usually went hand in hand.

Really, its a judgement call.

Will stopping the drips be too dangerous to justify? Sometimes yes, sometimes no. Depends on the patient and what's running.

Will having the drips stay running screw up your sample? Sometimes yes, and sometimes no. Depends on whats running (and how fast) and what youre drawing.

And, frankly, if you don't know how much of a risk you're taking in any given situation, you shouldnt be drawing out of the cvc. Go grab a needle and a tourniquet. Get some practice with the ultrasound if you must.

Also, follow facility policy, yada yada yada.

Research into this topic has "not established the length of time for stopping fluid flow" according to Infusion Nurses Society (INS). One study suggested a wait time of 10 minutes before drawing your blood sample (when drawing from a CVAD).

When drawing from a short term, less than 3 inch IV catheter, stop your infusion for at least 2 minutes prior to the lab draw. Then, waste 1 to 2 mls.