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Louise cofield
drawing blood from a central line with a clear link cap

When drawing blood from a central line that has a clear link injection cap, should the clear link cap be removed to draw the blood or should it be left in place to draw the blood? If it is left in place and the blood is drawn, should the cap be replaced with a new cap past the blood draw?  

Louise Cofield Clinical Educator

Louise cofield
blood draws from central
blood draws from central lines
There are no true evidence

There are no true evidence based answers to your questions. We know that all needleless connectors grow biofilm and therefore produce the risk of bloodstream infection. We know that should be changed at least as often as the change interval for primary continuous infusion sets - usually every 72 or 96 hours. We know that some have been tested by the manufacturer to 7 days. We also know that residual blood is a great medium for the growth of organisms that are being introduced. 

So is it safer and more effective to draw blood from a needleless connector rather than open the entire system and connect hub to hub? Possibly, if you are thinking about the risk of air emboli, etc. Can you also be totally successful with drawing from the needleless connector? Maybe or maybe not, as this could produce some additional resistance to obtain the amount of blood needed. Is it possible to adequately flush all of the remaining blood from any of the needleless connectors? Some manufacturers have data on this, but not all. And you must remember that there can be 1 million RBCs in solution without any change in color. 

How frequently are catheters used to draw blood samples? How often will this mean that the line is opened and the connector must be replaced? I know I have given you more questions than answers, but that is the nature of this beast right now. 

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

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

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