Posted by: medicblog999 | June 30, 2009

Pet hate!


If I am assessing a patient for IV access and their veins are really poor, I am likely to ask for a 20g.

Some paramedics seems to think that:

“You cannot give fluids through anything smaller than an 18g”

I tend to respectfully disagree (see what I did then, I always said this wouldnt be a ranting blog!!)

If I need to give a patient fluids, be that just 100mls of IV Glucose, or volume for a popped Abdominal Aortic Aneurysm, rest assured that I will always put in the biggest possible cannula that the vein can take (as required for the condition, I wont ever be putting in a 14g or 16g for a diabetic). If the patient has veins that will take a 14g and they need volume, then they will get a 14g. If the patient needs volume, but is a little old lady with tiny thread veins that look like they will blow as soon as you look at them, then she will get a smaller one, possibly even a 20g.

A small cannula is better than no cannula at all chaps!

In the next post I will write about a patient who’s only access I could see was for a 22g into the vein at the base of his right thumb. Yes, its a teeny tiny cannula, but its big enough to give someone some morphine through. The job following that one was to a motorcycle RTC where the patient got a 14g cannula in both arms.

I am not afraid of the big cannulas, I just see each patient as an individual with individual anatomy which needs to be assessed for their own unique needs. We need to become more flexible in our assessments for IVs, and even consider if the patient needs an IV at all (But that’s for a future post)


  1. I have to agree with you Mark when it comes to gaining vascular access. If you know an 18G or bigger will just blow the vein then why even bother. Would you rather infuse the fluid or medication slower or not at all. I know what my choice would be. Do you have the option of intrasosseous if they have no veins? I have used it a few times and it works fantastic.

  2. I’ve heard that stuff too about cannula size. But in the end access is access and if the patient is dying than who really cares how big it is? I’ve even put a 24 in a guys thumb, I’ll take what I can get.

  3. we have the EZ-IO and it uses what looks like a small cordless drill and I have seen videos of it being used on live patients and it supposedly hurts about as much as a regular IV….still i wouldnt want one done on me if im awake.

  4. Most of the crews who come in are excellent and appropriate, but I’ve seen some really dumb things (usually, it has to be said from private crews) – like a 14G in a 95ish year old woman with terrible veins. The fluids weren’t going into a vein; looking at her arm and the amount of fluid gone from the bag I’m not convinced it was in for more than a few seconds 😦

    Good reliable access is better than something big that’s going to tissue the second time you use it. And despite my trauma training saying 14 or 16G I’ll take what I can get, initally.

  5. ultimately when it comes to access ‘any hole is a goal’ i’d much rather see a patient witha patent 20g than umpteen holes from failed bigger lines

  6. Even aneasthetists have trouble cannulating me. I’ve had them in my thumb before, and right on the kunckle (that’s my best giving blood vein!). And after 8 attempts at a more normal place, I had one in my foot as that was the only patent vein they could find – 24 hr IV infusions are not the best through a cannula in your foot!

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