News | September 14, 1999

I.V. Q & A: Drawing Blood Samples from Lines

Editor's Note: Have questions about infusion therapy? I.V. Q and A is the place to look for answers. Check back weekly for a new question related to the placement, use, and maintenance of I.V.s.

I work in a busy emergency department (ED) in Southern California. We're looking into drawing blood samples from established I.V. lines or saline locks. Do you have any research on this practice?

This is a common query among many nurses who are looking not only to save time but also to save their patients from excessive discomfort.

If you have Internet access, please log onto You'll see a heading entitled "Standards." This is the Intravenous Nursing Standards of Practice, revised 1998.

Standard of Practice #33 addresses blood drawing from pre-existing cannulae and IV administration lines/sets. As you'll see, indwelling devices aren't recommended for routine blood draws. But obtaining blood while inserting the cannula is perfectly permissible. The device is "virginal," if you will, in that no medications or infusates have been infused via the device. This is also a plus as several lab results may be affected by certain medications that are known to adhere to certain catheter materials. This includes aminoglycosides, vancomycin, and heparin.

In some situations, frequent lab sampling may be required for acute hemodynamic monitoring. If this is the case, peripheral cannulae may be inserted for this express purpose. Follow your organization's policies: No infusate/medications are ever infused using this dedicated device until the need for blood-drawing access has passed. The venous access device (VAD) may then be used for infusion purposes.

From an infection control point of view, attempting to withdraw blood samples via the administration set is contraindicated. You risk poor sampling along with the introduction of microorganisms into the infusion delivery system and finally into the patient's vascular access system. What's more, blood will most assuredly clot within the tubing's lumen because of its incompatibility with most infusates, with the exception of 0.9% normal saline solution.

You're probably wondering where centrally located vascular access devices (CVADs) fit into the earlier discussion. Should an ED patient be so ill as to require placement of a multilumen CVAD, many clinicians will prefer this type of device for blood-drawing and monitoring. These devices are perfect for lab sampling as the lumens are staggered, which facilitates multiple infusion modalities and prescriptions. Check on your organization's policies for lab sampling from CVADs. Also check with the specific manufacturer about practice guidelines and recommendations for use of individual catheter products.

Reprinted with permission from the INS Newsline, Intravenous Nurses Society, Cambridge, MA; These questions come from I.V. clinicians and are answered by Debbie Benvenuto, CRNI, INS Nurse Educator/IV Therapy and coordinator of the INS National IV Nursing Network.

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