Blood drawing with IVs.

Q How long should an IV be shut off before a peripheral blood sample is drawn from the same arm?

A The Clinical and Laboratory Standards Institute (CLSI) is quite detailed in its venipuncture standard on the proper procedure for drawing blood from a patient receiving IV fluids. (4) Although the literature is not in agreement on whether or not drawing above an active IV is acceptable, CLSI states that draws from the same arm as an infusion should be avoided if at all possible.(1-4)

If unavoidable, CLSI suggests collectors ask the infusion nurse to shut off the IV for two minutes prior to the puncture, tighten the tourniquet below the IV site, and perform the puncture as usual. Some authors and studies suggest discarding the first 3cc to l0cc of blood. (5-6) All draws from the same arm as an IV infusion should be documented as such. Shutting off the IV for longer than two minutes risks occlusion of the IV, which may necessitate the nurse removing it and starting it in another vein. Given that IV placement can be extremely difficult in some patients, this puts the patient at risk of a dangerous delay in the infusion of critical IV fluids.

Drawing blood above an IV is a risky proposition, even when it is temporarily discontinued. Studies show that accurate lab results can be obtained when the IV is shut off for three minutes and the first 5cc discarded; however, one must consider the infusate. If drugs were being infused, the specimen for assay of that drug should not be collected above the IV (3) Likewise, if heparin is being infused, coagulation studies should not be drawn proximal to the infusion. If the facility permits specimens to be drawn above temporarily discontinued IVs, CLSI recommends labeling the specimen as such. (4)

Before implementing such a policy, consider the potential for serious consequences. What if tests get added on to specimens hours after they were drawn above an IV? If the add-on tests are for analytes that were infused, the results will likely be inaccurate. What if the limitations to this practice are not communicated to all who collect specimens in the facility? If your facility has non-laboratory personnel as well as phlebotomists drawing specimens, someone may observe a phlebotomist drawing above an IV for labs that do not include what is being infused and conclude that it is universally acceptable. The exceptions fall to the wayside; and, before you know it, the lab is receiving contaminated specimens. In some situations, allowing blood to be drawn above an IV is a perilous policy.

--Dennis Ernst, MT(ASCP)

Director, Center for Phlebotomy Education

Coalition for Phlebotomy Personnel Standards Ramsey, IN

References

(1.) Watson R, O'Kell R, Joyce J.Data regarding blood drawing sites in patients receiving intravenous fluids. Am J Clin Pathol. 1983;79(1):119-121.

(2.) Read D, Huberto V, Arkin C. Effect of drawing blood specimens proximal to an in-place but discontinued intravenous solution. Am J Clin Pathol. 1988: 90(6): 702-706.

(3.) Savage R, ed. Q&A column. CAP Today. 2002; 16(4): 102-103.

(4.) Clinical and Laboratory Standards Institute. Procedures for the Collection of Diagnostic Blood Specimens by Venipuncture, Approved Standard. Wayne, PA: Clinical and Laboratory Standards Institute; 2007. CLSI document H3-A5.

(5.) Dale J. Preanalytic variables in laboratory testing. LabMed. 1998; 29(9): 540-545.

(6.) Mohler M, Sato Y, Bobick K, Wise L. The reliability of blood sampling from peripheral intravenous infusion lines. J Intravenous Nursing. 1998; 21(4): 209.

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Edited by Daniel M. Baer, MD

Daniel M. Baer, MD, is professor emeritus of laboratory medicine at Oregon Health and Science University in Portland, OR, and a member of MLO's editorial advisory board.