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  1. #1
    Junior Member paris's Avatar
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    Does it matter what size syringe used?

    Someone told me that for instance when administering a 5ml solution (bolus), one should use a 10ml syringe, as this reduces the force exerted upon the vein. I thought that the solution is injected via cannula anyway so the size of syringe used make no differance.

    Can someone explain this please.

    Thanks



  2. #2
    Senior Member Varied A's Avatar
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    The only time you would be administering the drug fast enough to exert force upon the vein is in an emergency, when really it's the least of your worries. Almost all IV injections should be given over a period of minutes rather than all at once. Furthermore, you should be using the smallest size cannula possible, which will further reduce the pressure on the vein.

    All of that combined with the fact that I've never heard of doing what you said nor can I find any info on it suggests to me that it's probably not nescessary...
    John

    Mark:- Dr Carter, you seen Dr Weaver?
    Carter:- err usually she's everywhere

  3. #3
    Junior Member paris's Avatar
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    Quote Originally Posted by Varied A
    The only time you would be administering the drug fast enough to exert force upon the vein is in an emergency, when really it's the least of your worries. Almost all IV injections should be given over a period of minutes rather than all at once. Furthermore, you should be using the smallest size cannula possible, which will further reduce the pressure on the vein.

    All of that combined with the fact that I've never heard of doing what you said nor can I find any info on it suggests to me that it's probably not nescessary...

    In ophthalmic we inject 2.5 mls of Fluorescein dye all at once followed by: number of photographs taken at interval from 10-20 seconds after injection of dye and at late phase at 5 minutes and on. The question is dose it make any differance whether we use 5mls or 10 mls syringe regardless the size of the venflon excerting pressure on the vein?

  4. #4
    Senior Member Varied A's Avatar
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    Erm, fluorescein only comes in eye drop form, I'd hope that you're not injecting that?! :s
    John

    Mark:- Dr Carter, you seen Dr Weaver?
    Carter:- err usually she's everywhere

  5. #5
    Senior Member belis's Avatar
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    Quote Originally Posted by Varied A
    Erm, fluorescein only comes in eye drop form, I'd hope that you're not injecting that?! :s
    It does not. Fluorescin sodium can be injected to produce a fluorescein angiogram.

  6. #6
    Senior Member Varied A's Avatar
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    Quote Originally Posted by belis
    It does not. Fluorescin sodium can be injected to produce a fluorescein angiogram.
    Interesting, I just googled fluorescien angiogram - 6 weeks in ophthalmology earlier this year obviously did me no good. I'm intrigued though as to why it's not in the BNF for this use?

    Referring back to the original question, you got me intrigued - I've looked through a couple of nursing procedure books and some articles on IV administration, and can find nothing about it, and so I still think it's rather unlikely that a 10ml syringe would offer any benefit.
    John

    Mark:- Dr Carter, you seen Dr Weaver?
    Carter:- err usually she's everywhere

  7. #7
    Member andy2's Avatar
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    Several misconceptions here
    1) Pressure from a syringe is simple physics (i.e. pressure=force/area) hence one will develop a higher pressure with a two ml syringe than a 10 ml. This is why if you are trying to unblock a cannula a 2ml syringe is better.
    2) As long as you are injecting into a peripheral vein then the difference in pressure developed should not make any difference- veins are relatively high capacitance vessels and will expand to absorb the increased volume.
    3) contrary to much nursing teaching many IV drugs can, and should, be given rapidly - this is what I do as an anaesthetist every day. There are some drugs which have to be given slowly (as examples vancomycin, phenytonin and amioderone outwith arrest situations) but the great majority can be bolused fairly rapidly.
    4) Cannula size- although a smaller cannula will have a greater resistance to flow, and so cause a greater drop in pressure along its length, the most important determinant is the driving pressure. Small cannulae cannot provide the higher flow rate of larger cannuale (again simple physics/Hagen Pousille equation). There seems to be a trend towards putting small cannulae in large veins - this is annoying as it removes a site of venous access for a decent sized cannula, and if the patient needs fast fluids makes this nigh on impossible. With a wee dod of lignocaine larger (18G+) cannulae are no more sore to site than small ones and are a damn sight more use. They also last longer as they are less likely to kink. If you must insist on 20/22G cannulae then please put them in the hand/wrist veins and not the juicy ones in the ACF.
    Last edited by andy2; 19-11-2006 at 01:50 PM.

  8. #8
    Senior Member Varied A's Avatar
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    Quote Originally Posted by andy2
    Several misconceptions here
    If you must insist on 20/22G cannulae then please put them in the hand/wrist veins and not the juicy ones in the ACF.
    That could have something to do with the insistance of doctors that nurses only cannulate or take blood from the ACF and do not go anywhere else
    John

    Mark:- Dr Carter, you seen Dr Weaver?
    Carter:- err usually she's everywhere

  9. #9
    Member andy2's Avatar
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    Although this relates only to my personal experience I've never met a doctor who insisted nurses only cannulate the ACF -if they are doing this they need serious re-education. I've met plenty of nurses who insist they should only cannulate the ACF, and only use pink/blue venflons but that is usually down to
    a) unwillingness to have to go through the 'failure' required to improve ones skills and b) BS teaching by 'practice development nurses' who spend a lot of time teaching skills they are hardly proficient in themselves. (i.e. if you can only cannulate the ACF then you cover this up by inventing spurious reasons as to why your students should only do this).

    Cannulation is a simple motor skill, and only gets better with practice - the only reason I'm pretty good at it is because I've put in several thousand in the past couple of years.
    FWIW the ACF is also a more hazerdous place to cannulate as you are more likely to inadvertenly cannulate the brachial artery -which risks direct arterial damage, distal ischaemia and inadvertent intra-arterial injection. This is one reason why I avoid the ACF unless it is the only option. Given how risk averse most nurses are I think if they knew this they'd avoid this area too.

  10. #10
    Senior Member Varied A's Avatar
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    I agree with you, many don't! I've had discussions with many nurses over these kinds of issues, and certainly in the trust I predominantly work for, the cannulation policy (which was written by a senior doctor with no nursing input) quite clearly states that nurses must only cannulate or take blood from the ACF.
    John

    Mark:- Dr Carter, you seen Dr Weaver?
    Carter:- err usually she's everywhere

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