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Collecting Heparin Assay Specimens from a Device

Dear George Fritsma, I work at The Valley Hospital in Ridgewood N.J. and our nursing staff has the following question about drawing an APTT from a central line/picc line when heparin is infusing. Is there a protocol of how long to stop the infusion? Also, should the first syringe be discarded? I am interested in knowing how other hospitals handle and advise their phlebotomy and nursing staff on this issue. Mrs. Linda Sherman-Atkins MT (ASCP) SH.

Hello, Mrs. Sherman-Atkins, and thank you for your question, which I answer below using a section excerpted from Bennett A, Fritsma GA, Quick Guide to Venipuncture, AACC Press, 2010. Please forgive the self-reference:

To collect blood using a vascular access device (VAD), the blood collection device—an evacuated tube or syringe—must match with the VAD diameter and connection design. Attempts at blood collection with an incompatible device may introduce sepsis or an embolus, may damage the VAD, and may result in a useless clotted or hemolyzed blood specimen.

The VAD and collection device are disinfected and managed aseptically. Before collecting blood the line is flushed with several milliliters of saline or heparin. Then 3–5 mL of blood are collected and discarded to eliminate the risk of specimen contamination before proceeding with the collection. If collecting from an intravenous line, the drug infusion is discontinued for several minutes prior to blood collection. Certain drugs—narcotics, for instance—require steady-state administration and may not be stopped; likewise RBC transfusions may not be stopped. Personnel must know which drugs are safe to stop.

Upon completion, the VAD is again flushed and sealed, and the port is again disinfected. Intravenous infusions must be restarted. Specimens are labeled in the patient’s presence and managed the same as specimens collected by venipuncture, including order of draw, mixing requirements, and transport times. Each blood collection, drug administration, and flushing fluid is recorded in the patient’s chart.

I hope this is helpful. Two Clinical and Laboratory Standards documents are available to provide authority for hemostasis-related phlebotomy decisions, they are CLSI. Procedures for the Collection of Blood Specimens by Venipuncture; Approved Standard-Sixth Edition. CLSI document A3-A6. Wayne, PA: Clinical and Laboratory Standards Institute, 2007 and  CLSI. Collection, Transport, and Processing of Blood Specimens for Testing Plasma-Based Coagulation Assays and Molecular Hemostasis Assays: Approved Guideline-Fourth Edition. CLSI/NCCLS document H21-A5. Wayne, PA: Clinical and Laboratory Standards Institute, 2003. A caveat: my references are old, there exists updates for both documents from CLSI.

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