IV Gauge for CT

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In the ER today I had a 20 y/o "chest pain." Of course the pt received the full cardiac workup as well as a CT of the chest. Prior to taking my pt to CT the MD asked me what size IV I put in the patient and I replied 20 G. In my opinion, I felt this size IV was sufficient. However, the MD, who is newly off residency, snapped back and said I want an 18 G in this patient. I proceded to question why and he said that he could (not sure why he said he bc it is the radiologist who does this) could read the scan better. I had my doubts but let the fight rest because for one I had no time for this and two I knew it would get me no where, fast. He put in an order for the 20 G to be DC'd and an 18 G LAC placed. I spoke to a few seasoned nurses as well as rad tech's who have never heard that the size 20 or 18 G made a difference on the scan. Anyone knowledgeable in this area??

Specializes in Cath Lab/ ICU.

I don't need a doctors order for IV placement. I would have left the other IV as well...

Besides, if the policy of this hospital was not to use 20g, then the CT tech wouldn't use it anyway. No need to pull it out. I'd cover it with coban and let little Dr think he had his way.

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Specializes in OR, peds, PALS, ICU, camp, school.
i beg your pardon, but an invasive procedure such as an iv insertion absolutely requires a doctor's order. if the doctor says to d/c it, it is a medical, and not a nursing judgment.

"...sorry, it's the nurses not the md's business if there is an extra iv"

i would like to see you go to your state bon with that line of thinking; they'll pull your license so fast your head would spin.

over a second peripheral? frankly, the bon can have it. i'd be over it.

i don't need a doctors order for iv placement. i would have left the other iv as well...

besides, if the policy of this hospital was not to use 20g, then the ct tech wouldn't use it anyway. no need to pull it out. i'd cover it with coban and let little dr think he had his way.

maybe it's a facility thing? none of the hospitals i have worked at require an order. it's all policy. if and md orders an iv med, we need to put in an iv. if they're on tele, the need an iv, if they're in a unit, they need two. if we think they need two, we put in two. if the pt complains that the ac is uncomfortable we put in another. if it's outdate, we d/c and put in a second.

if your facility protocols state that iv size, location, and existance is at the sole discretion of the dr, then by all means, don't have two just because i would. every "reasonable prudent nurse" knows that facility p&p outweighs the opinions and experiences posted here.

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Specializes in ER.

Three hospitals I worked ER in wanted a 20 in the AC. Where I am now, if we can't get the access they want we send them over and the radiologist pulls out an US machine a puts in what they want. That makes sense to me. If they require a particular IV then they can do the work. Of course we keep their preferences in mind when we start our lines, but they have become responsible for getting their own access if they don't like ours.

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Specializes in Telemetry/IMC.

In the facility I work at now, they prefer an 18g to the AC, but will accept a 20g. They don't really bend on the placement either, which makes sense because of the need for a large vein. Plus I've always been told that part of CP protocol is to insert a large bore IV (once again 18g preferred) so if they need to push fluids or (what have you) they can. Just my little contribution to this topic :nurse:

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Specializes in Emergency.
We had a 21 yo male with a STEMI in the ED a few weeks ago.

We don't work up every 20 yoa cp that comes in the ED, doesn't mean they don't get EKGs.....

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Specializes in ED, CTSurg, IVTeam, Oncology.
Over a second peripheral? Frankly, the BON can have it. I'd be over it.

Maybe it's a facility thing? None of the hospitals I have worked at require an order. It's all policy. If and MD orders an IV med, we need to put in an IV. If they're on tele, the need an IV, if they're in a unit, they need two. If we think they need two, we put in two. If the pt complains that the AC is uncomfortable we put in another. If it's outdate, we D/C and put in a second.

If your facility protocols state that IV size, location, and existance is at the sole discretion of the Dr, then by all means, don't have two just because I would. Every "reasonable prudent nurse" knows that facility P&P outweighs the opinions and experiences posted here.

Forgive me, but the thing that I see repeatedly, is that many nurses don't seem to understand, is that there is NO hospital policy anywhere that supercedes state nursing license rules, requirements, OR restrictions. That is, your employer cannot tell you to perform acts for which you are not legally licensed (and believe you me; with nurses, many employers do try).

Hospital "policies" (or "protocols") are essentially standing (ie prearranged) medical orders that are signed off by medical committees ahead of time in order to allow nurses to act fast in cases of emergencies, or for common and routine acts which don't require repeated and close MD contact. They will eventually need to be countersigned by the primary physician if he or she concurs, or if not; can be rescinded. The fact remains that they are only medical order guidelines for physicians and nurses and can be retracted by the primary physician at any time. In other words, a bedside MD can just as easily discontinue any policy facilitated standing order (which had allowed nurses to legally act), which in this case, the primary doctor did do, by saying that the particular IV is to be removed.

Thus a nurse who decides to go against a doctor's medical decision, and keep in an IV in direct opposition to a physicians order would be treading on some very precarious legal ground; it's otherwise known as practicing beyond your scope. The other suggestion of keeping the thing covered to deceptively mislead the doctor into thinking that his order was carried out is not only practicing beyond scope, it is rather childish and unprofessional, IMHO.

I've seen plenty of arguments with less than smart doctors over the course of a quarter century, and I've seen plenty of other nurses who have done exactly the same. But none had ever won any argument that violated conditions of license as you advocate.

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this is a question related to physics.

but... (and respondent odelle brushed upon this)

...the amount of pressure during the injection will be vastly different. if you use say, ...a 24 ga catheter, just imagine the amounts of pressure required to push 10 ml within 2 seconds, through it; would it be high or low? answer; it would be strikingly high. would the machine still be able to do it? of course it could; it is an unthinking machine that is geared to delivery that volume over that set time, regardless of the pressure that it generates. so what would happen to the vein that is on the other side of that catheter? almost immediate rupture.

now since that first iv was in the antecubital vein, and most patient's only come to the hospital with two; you've just ruined one. so... if you want to do the study, you can only get one more try. hence, the larger the catheter, the less pressure there is at the injection site, and less pressure means less likelihood of vein rupture or infiltration which indirectly allows them to complete the study at the prescribed protocol rate.

btw, great question :up:

as for the md being nasty to you? well, aside from clinical rationales, some people are just plain ill tempered regardless of their stripe. don't let it get to you.

close, but not exactly correct.

what actually increases is the differential pressure required across the restriction (catheter) to overcome the higher resistance of a smaller catheter in order to obtain the same flow volume over time. the higher pressure is all on the upstream side of the catheter, not at the discharge end in the vein. anyone that claims otherwise has insufficient knowledge of fluid dynamics. what does increase at the discharge end of the catheter is velocity, which is proportional to the cross sectional area of the catheter - smaller catheter diameter = higher discharge velocity for the same volume over time.

as long as the injection pump is capable of the necessary pressure and the tubing and catheter are rated to withstand it as well, it shouldn't matter all that much as long as the vein is capable of handling the flow.

that said, a high enough velocity could result in more turbulent flow and increased mixing of the contrast with the blood, diluting it somewhat. if the test depends on the contrast remaining as much as possible a cohesive bolus, then this could potentially adversely affect that.

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We don't work up every 20 yoa cp that comes in the ED, doesn't mean they don't get EKGs.....

There are plenty of young or relatively young people that come into my ED that don't get a complete CP workup, but are evaluated on a case by case basis. That may be stating the obvious, but your original statement sounded like you would automatically discount anyone that young with CP and never consider them for an MI.

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Specializes in ED, CTSurg, IVTeam, Oncology.
Close, but not exactly correct.

What actually increases is the differential pressure required across the restriction (catheter) to overcome the higher resistance of a smaller catheter in order to obtain the same flow volume over time. The higher pressure is all on the upstream side of the catheter, not at the discharge end in the vein. Anyone that claims otherwise has insufficient knowledge of fluid dynamics. What does increase at the discharge end of the catheter is velocity, which is proportional to the cross sectional area of the catheter - smaller catheter diameter = higher discharge velocity for the same volume over time.

As long as the injection pump is capable of the necessary pressure and the tubing and catheter are rated to withstand it as well, it shouldn't matter all that much as long as the vein is capable of handling the flow.

That said, a high enough velocity could result in more turbulent flow and increased mixing of the contrast with the blood, diluting it somewhat. If the test depends on the contrast remaining as much as possible a cohesive bolus, then this could potentially adversely affect that.

Thank you for your observations, but I respectfully disagree.

Your usage of fluid dynamics theory is absolutely correct, but your real life application of it in this case IMHO, is not entirely on the mark. Fluid dynamics in a solely mathematical exercise is exactly as you had stated. However, in actual usage in a real vein, the pressure difference does not disappear or dissipate instantaneously; the higher velocity discharge right at the tip of the catheter against the wall of the vein translates to additional pressure gradient that prones a vein to extravasation. Like respondent Odelle's CT work experience so eloquently stated; 20 ga catheters, when power injected, tend to infiltrate at a greater rate than 18 ga's.

Additionally, your fluid velocity vis a vis turbulent mixing idea is correct, but again, the application of it in this case IMHO, also remains irrelevant. In real life usage of powered injectates into a peripheral vein, the increased pressure of the injection process effectively closes the venous valve of that particular vein, effectively preventing any blood from being allowed to mix with the injectate. Venous return at that moment will simply shunt around that vein as the pressure in it (at the moment of injection) is too high for a low pressure venous system to overcome. Thus, the injectate flows as a bolus with almost no mixing until it gets into the central circulation. Since the volume of the contrast bolus injected remained the same, by the time it actually gets into the central circulation, the velocity of the injectate at the injection site IMHO, thus becomes moot.

I welcome your learned consideration of this and continued discussion of what has become a fascinating topic.

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Specializes in ER/PICU.

Been using 20's almost since CT PE came into being. 18 is preferred but 20 will do just fine. You will need to check w/CT though about extension PRN adaptors. Those with tubing may not be able to take the pressure infusion of IV Contrast.

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Specializes in Emergency.

Usually a 20, sometimes an 18, always above the wrist. Haven't had one infiltrate, but there's always a first time.

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Specializes in Emergency.
There are plenty of young or relatively young people that come into my ED that don't get a complete CP workup, but are evaluated on a case by case basis. That may be stating the obvious, but your original statement sounded like you would automatically discount anyone that young with CP and never consider them for an MI.

Oh, come on! The OP put chest pain in quotation marks! We all know what that means.

Not sure how triage works in your house, but in mine, it demands that everyone is evaluated on a case by case basis.

I thought this post was about IV size, not my person opinions about young people with CP that has no bearing on how I treat them professionally.

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