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Length of time stopping heparin IV/ TPN for blood draws

 I would like to clear up some misinformed staff and lab personal on protocol for lab draws from PICCs/Ports.  When a pt has a heparin drip or TPN infusing through a single lumen chest port or PICC, I have heard staff from lab or nurses seem to think the IV has to be turned off for 10-15 min before drawing labs.  I realize drawing a peripheral stick is preferred but sometimes this is not a option for a pt. with poor IV access.  I don't think staff is aware of the blood flow per minute through the SVC.  Could you please address this or provide current articles that I could site to help lab staff and nurses become more familiar with proper protocol.

Thanks so much,



 I have never seen any

 I have never seen any research or good evidence to establish an exact time for this. However I can tell you that only 1-2 minutes should be sufficient due to the rapid blood flow in the SVC. Leaving TPN turned off for 15 minutes could be harmful for the patient depending on how well controlled their blood glucose is. Turning off a continuous heparin infusion for 15 minutes will negatively impact the coag values. This is simply not reasonable. There could be some studies that have assessed the accuracy of lab values when drawn from a CVAD that includes the length of time the infusion was stopped when the researchers reported their protocol. This would require a literature search and assessing the contents of those studies. Check out this dissertation I just found but it contains lots of complex equations:



Lynn Hadaway, M.Ed., RN, BC, CRNI

Lynn Hadaway Associates, Inc.

126 Main Street, PO Box 10

Milner, GA 30257


Office Phone 770-358-7861

Check with the lab and AABB

Check with the lab and AABB guidelines I believe it says 2 minutes, that is our policy here now.


BJ Sherman, RN

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