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PTT draws through central lines

What are all of you doing regarding drawing PTT's through a central line?  Do you stop the med?  How long?  Do you use a lumen that the med is not infucing through (if possible)?  How much waste?  How much flush?

This question refers to the pt. polulation in which a peripheral stick is not possible.

As always, thanks for sharing your knowledge!



Are you using heparin lock

Are you using heparin lock solution in these lines? If so, your lab data may not be accurate. An NIH study reported that it required a discard volume of 25 mL before they were able to get correct values on coag studies. Here is the reference:

1.    Mayo DJ, Dimond EP, Kramer W, McDonald KH. Discard volumes necessary for clinically useful coagulation studies from heparinized Hickman catheters. Oncology Nursing Forum. 1996;23(4):671-675.

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

anna liang
most post liver transplant
most post liver transplant babies go home with tunnelled catheter for frequent lab draw in out-patient. those lines are hep-lock and PT/PTT are routinely drawn.
nobody will waste 25ml of blood for infants.
will check with the team if they noticed higher pt/ptt 
Karen Day
Karen Day's picture
we do not allow lab draws
we do not allow lab draws such as this through any of our central lines.  We also do not do peak and trough through lines that the medication infuses through due to previous false results (i.e. abnormally high troughs etc.)
anna liang

please see link above.

When I asked one liver transplant NP today, she said all coag tests drawn from hep-locked central line are labled 'hepasorb' on the lab slips. only will repeat peripheral draw if the tests come back 'abnormal'
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