what size syringe is used to flush triple lumen?

[cmv]

there is a question upon which size syringe to flush triple lumens with. the larger the syringe the less force it exerts?? ports 10 cc, same for triples??

[S.Lunsford RN]

Our policy is 10 cc syringe for all central lines

[Fgr8Out]

Originally posted by Agnus

I was taught not to use a 3 cc or smaller.

HOWEVER, I firmly believe nursing has it backwards. The larger the syringe the > the pressure. Because you have a bigger serface area inside the syringe which creates higer presssue.

Ask any plumber when you have a big pipe feeding into a small pipe it creates greater pressures inside the small pipe.

Has not one notice you must apply greater force when using a bigger syringe because you are trying to force a large surface area into a small one?

Think about this for a second. Say you are putting water though a NG with a 50 cc syringe using the plunger. Then say you take a 10 cc syring to deliver a dose of med into the same NG. It will take less force to deliver 10 cc thought the small syring than 10 cc thought the large one because there is less resistance because the size gradient change between the syring and the tube is less.

~*~*

The force may appear to be greater... but the amount of pressure exerted to flush the lumen is actually less. The greater force you believe is being exerted is due to the smaller lumen of the line... not due to the size of the syringe.

"When infusing IV fluids via syringe, the key pressure issues are force and internal diameter. The hand exerts force (F) across the syringe plunger (A). Applying the same force, a 3mL syringe produces a higher pressure than a 10mL syringe. " Resistance and Pressue in Effective IV Therapy, http://www.baxter.com/doctors/iv_therapies/education/iv_therapy_ce/pressure/pressure.html#dyn

Here is the math: A 10cc syringe has a diameter (A) of 16mm. A 3cc syringe has a diameter (A) of 7mm. If, for example, the force/pressure exerted (F) is 50... then for a 10 cc syringe 50(F) divided by 16(A) = 3.125 psi. In the case of the 3cc syringe, 50 (F) divided by 7(A) = 7.15 psi.

THAT is the rationale for using the larger syringe for flushing... in this case, bigger IS better.

[Agnus]

Thanks, I can't seem to digest this at the moment. But then it is 0530 a. m. I will print this and try to understand it later.

It is ineresting as just yestertay someone reminded me (on a non related topic) that it takes more force to "draw" fluid through a narrow straw than a wide one.

I have been tring to relate it to this problem but have not completely gotten it yet.

My thinking seemed so right but I also know that if it is and established standard there is a reason and that I am probably missing something, which I am (minimaly) starting to see is the situation.

Math is not my forte. I just do not think in mathmatical term. But I will look this over and see if I can decifer it to term I can comprehend.

The CE link you refer to looks promising

[Fgr8Out]

Originally posted by Agnus

Thanks, I can't seem to digest this at the moment. But then it is 0530 a. m. I will print this and try to understand it later.

It is ineresting as just yestertay someone reminded me (on a non related topic) that it takes more force to "draw" fluid through a narrow straw than a wide one.

I have been tring to relate it to this problem but have not completely gotten it yet.

My thinking seemed so right but I also know that if it is and established standard there is a reason and that I am probably missing something, which I am (minimaly) starting to see is the situation.

Math is not my forte. I just do not think in mathmatical term. But I will look this over and see if I can decifer it to term I can comprehend.

The CE link you refer to looks promising

~*~*

Oh I hear you there, Agnus... believe me. I am NO mathematician by any stretch of the imagination. I wish I could explain to you the demonstration our CNS gave us when explaining the principles behind this... alas, I don't recall it at the moment. I'll ask her again when I return to work next week and PM you with it.

Peace :)

[fins]

Agnus,

Here's a non-math way of looking at it. Put your palm against your cheek and push against your cheek. Next, put the point of your index finger against your cheek and push just as hard. Which hurts more? The finger.

The force (how hard you push) is the same in both cases, but in the case of your finger, all of that force is "concentrated" into a smaller area (the tip of your finger.) That's what pressure is, when you get right down to it.

So actually, it isn't really about how many cc's the syringe holds, it's about the diameter of the syringe. It's just that 10cc syringes happen to have a wider diameter than 3cc syringes. However, if a smaller syringe had the same diameter, then the pressure would be the same. (Like those 2cc NS flush syringes they use at my hospital - they're the same width as a 10cc syringe.)

Hope that helps.

[Fgr8Out]

Originally posted by fins

Agnus,

Here's a non-math way of looking at it.

perfect... thanks Fins :)

[BadBird, BSN, RN]

I have to agree, I use 10cc or larger.

[Burnt Out, ASN, RN]

We don't have a policy on what size syringe to use to flush triple lumens-most of the time we use 3 cc or >. On ports it is policy to use 10cc or >.