Question about PICCs and syringe size

Specialties Infusion

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Hi all,

In the last NICU I worked at, and when I trained as a PICC RN, I was always told to never use less than a 5cc syringe when administering meds or flushes through the 1.9-2fr piccs used in neonates, unless placed on a syringe pump over a set time, eg 20 minutes. Here at my new job, no one seems to know what I'm talking about. Meds are routinely pushed with 1cc syringes. I'm afraid of catheter rupture. Who's right here??

I think some of you have forgotten that it does not matter what volume the syringe is but what diameter bore the syringe is.

Not all 10ml syringes are the same bore, although most are around the same diameter.

I have 3ml and 5ml syringes that are the same 14.5mm diameter bore as our 10ml syringes...

Pressure = Force Applied X Size of Area Being Forced Into

Think about this, I have two hoses with 1 gallon of water in each. (Volumes the same). One is 10ft long and the other is 100ft long. You apply the same 10lbs of force on either hose and the 100ft long hose is going to squirt water out at a much higher PSI.

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Specializes in Infusion Nursing, Home Health Infusion.

Yes but with a syringe you are not really talking about significant difference between manufactures of say a 10 ml syringe in terms of bore size. I have seen too many broken PICC lines that I ultimately had to temporarily repair or replace b/c of poor nursing care and most of these occurred b/c of too much pressure applied. So a valid topic to explore and we are not talking about just the cost of a peripheral restart. Yes it is frustrating to place a PICC and have to replace it 2 days later. Teaching nurses how to properly use and care for all types of CVCs is just an ongoing process.

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Yes but with a syringe you are not really talking about significant difference between manufactures of say a 10 ml syringe in terms of bore size. I have seen too many broken PICC lines that I ultimately had to temporarily repair or replace b/c of poor nursing care and most of these occurred b/c of too much pressure applied. So a valid topic to explore and we are not talking about just the cost of a peripheral restart. Yes it is frustrating to place a PICC and have to replace it 2 days later. Teaching nurses how to properly use and care for all types of CVCs is just an ongoing process.

I know, I feel your pain but what I am trying to say is the volume of the syringe is not important, the diameter is.

If you need to push smaller doses and want 3ml or 5ml syringes they make smaller volume syringes in the 14mm to 16mm bore size.

The range of bore diameter between the manufacturers only varies about 2-3 mm BUT that 2-3 mm does have an impact on PSI so people need to watch it.

P.S. I have found though too that there was too much pressure because people did not bother or the facilities did not want to roto-router the CVC with Activase. Funny/sad seeing a nurse clench down on a syringe attempting to infuse when all it would take is a $75-$100 single dose of Activase to save that $250-$2500 CVC

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Specializes in being a Credible Source.
Think about this, I have two hoses with 1 gallon of water in each. (Volumes the same). One is 10ft long and the other is 100ft long. You apply the same 10lbs of force on either hose and the 100ft long hose is going to squirt water out at a much higher PSI.
Actually, it won't, since the internal friction is so much higher on the longer tube.

As you correctly stated, this is only about cross-sectional area of the plunger and really has nothing to do with the volume of the syringe. It's just simple hydraulics and nothing more.

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Actually, it won't, since the internal friction is so much higher on the longer tube.

As you correctly stated, this is only about cross-sectional area of the plunger and really has nothing to do with the volume of the syringe. It's just simple hydraulics and nothing more.

$1,000 says it will. ;)

You are forgetting the concept in Fluid Dynamics called the "No-Slip Condition" where when a fluid contacts a surface the outside fluid molecules will stick to the surface and provide "lubrication" for the rest of the fluids. Most of the friction in a fluid actually occurs from the fluid molecules themselves as they move and bounce off one another.

Besides, the surface area of a set volume container is the same if you stretch that container out for 100 miles or squish it into a ball. Its the "Which glass has more water, the tall skinny one or the short fat one?" In fact they are the same.

If what you said was true then there would be no difference between using a 5ml 8mm bore syringe and a 5ml 15mm bore syringe when in fact there is a drastic difference in PSI.

For example, you take 65 grains of gun powder and put it into a cup and light and it will simply burn. Take that cup and stretch it into a long tube and light the powder and now you have a gun. Same amount of energy, same volume of container, just different diameter tube and much different amounts of pressure.

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Specializes in being a Credible Source.
$1,000 says it will. ;)

i used to be a betting man but now i'm reformed. :-)

you are forgetting the concept in fluid dynamics called the "no-slip condition" where when a fluid contacts a surface the outside fluid molecules will stick to the surface and provide "lubrication" for the rest of the fluids. most of the friction in a fluid actually occurs from the fluid molecules themselves as they move and bounce off one another.

actually, i'm not forgetting the boundary-layer effects though they have no practical relevance to this discussion. the velocity of the flow varies parabolically from zero at the boundary to the free-flow velocity some distance from the edge determined by the character of the fluid and the internal surface condition.

there is impedance to fluid flow (i.e. friction) throughout the length of the vessel just as there is resistance through the length of a conductor. just as it takes a larger voltage source to attain a given current in a small conductor, it takes a larger pump (i.e. higher pressure) to attain a given flow rate through a vessel.

besides, the surface area of a set volume container is the same if you stretch that container out for 100 miles or squish it into a ball. its the "which glass has more water, the tall skinny one or the short fat one?" in fact they are the same.

sure there is... i think i'm missing your point, though.

if what you said was true then there would be no difference between using a 5ml 8mm bore syringe and a 5ml 15mm bore syringe when in fact there is a drastic difference in psi.

no, i didn't say anything about cross-sectional area. well, actually, i did... and i completely concur that force is determined solely by the cross-sectional area. it's the classic hydraulics problem: p1a1 = p2a2.

i was challenging your comment (as i recall) that, for a given pressure, the flow would be faster out of a longer vessel than out of a shorter one.

for example, you take 65 grains of gun powder and put it into a cup and light and it will simply burn. take that cup and stretch it into a long tube and light the powder and now you have a gun. same amount of energy, same volume of container, just different diameter tube and much different amounts of pressure.

the difference between the gun and the cup is one of constrained expansion versus unconstrained expansion. you could argue (correctly) that a given round will have a higher muzzle velocity out of a longer barrel than out of a shorter one... but only to a point. the round will attain a maximum velocity when the friction of the barrel and the air creates a retarding force greater than the propelling force which diminishes by the square of the distance from the ignition.

totally different than what we're talking about.

(though i'm starting to think that perhaps we're not talking about the same thing)
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We have those same type syringes in 3cc. The manufactirer says that they have the same pressure as a 10 cc. None of us, including our PICC RN's trust it, so we still all use the 10cc.

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