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Vickie
Drawing blood from CVC with smaller syringes

Does anyone know of any restrictions or have any comments regarding syringe size when drawing blood from a central venous catheter?  I know that a 10ml or larger syringe is the standard for flushing CVC's but is it ok to use a smaller syringe for drawing blood from a CVC?  We recently had an incident regarding this issue and would like to know if there are any recommendations.    Thank You.

Mats Stromberg
Smaller syringe gives smaller negative pressure...

i.e. it is the opposite to when flushing: A small syringe will give smaller suction power than a larger syringe. Please share what the incident was and how it was handled.

Mats in Stockholm

lynncrni
On injection larger syringes

On injection larger syringes generate less intraluminal pressure when compared to the same amount of force applied to a smaller syringe. On aspiration, the opposite is true - larger syringes generate more pressure than smaller ones. think of it this way - the larger syringe has more surface area and therefore the nurse can pull harder thus generating more negative intraluminal pressure. What harm will this do to the catheter? I am not aware of any reports of catheter damage from this. Usually a soft catheter will collapse, obstructing the backflow of blood. But when the negative pressure is relieved, the catheter returns to it usual shape. I am curious to know about the incident if you can share that with us. Lynn

Lynn Hadaway, M.Ed., NPD-BC, CRNI

Lynn Hadaway Associates, Inc.

PO Box 10

Milner, GA 30257

Website http://www.hadawayassociates.com

Office Phone 770-358-7861

Vickie
Thank You for your

Thank You for your comments!

The incident that prompted this question was this:

The nurse was drawing labs from a central line.  The lab tech handed her a 3ml syringe.  The nurse informed the lab tech that only a 10ml syringe could be used for central lines.  The lab tech disagreed and stated it didn't matter what size the syringe was when drawing labs.  After a discussion with the lab manager, she requested evidence to support using only a 10ml syringe or larger for aspirating blood from CVCs.  As far as I know, there was not any damage to the catheter involved. 

Vickie Teresinski, RN, CRNI

lynncrni
The lab tech is correct. In

The lab tech is correct. In fact, when aspirating from a CVC smaller syringes may actually produce a larger blood return and allow you to collect more blood. Lynn

Lynn Hadaway, M.Ed., NPD-BC, CRNI

Lynn Hadaway Associates, Inc.

PO Box 10

Milner, GA 30257

Website http://www.hadawayassociates.com

Office Phone 770-358-7861

kathykokotis
article

Refer to Denise Macklin article in VAD on "whats physicis got to do with it" for your proof.  Larger syringe on push in gives more pressure per square inch and opposite applies on withdrawal due to physics

kathy

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