hi everyone and welcome to abc's of anesthesia now thanks very much for everyone who wrote in
to ask me some questions um so you had to ask me anything kind of episode just recently so thanks
for putting in all your questions and i'll try to get through all of them so one of the most common
questions that i get asked is can you rescue a failed iv cannulation attempt so let's get started
so i want to start off by saying in a word no that's probably the easiest way to answer
the question and now we'll go through a few of the reasons why so first of all what do i mean
so firstly the situation is you've got an adult patient
you want to do a peripheral venous axis so it's not a central vein it's not like internal jugular
vein or a femoral vein or subclavian vein or something like that it's a peripheral vein
and what happens is you attempt iv cannulation first of all imagine that you have a vein
and it just exists like that now you insert your needle and cannula
and so that's a needle and that's the cannula on top of it sorry for my drawing and then you try to
push the cannula off so it's not the cannula's not inside the vein you haven't advanced it far enough
therefore you have a failed attempt to cannulation you do get flashback however
so you get blood into the chamber so you're definitely in the vessel the second option is
you enter the vein you get flashback but then you go through one of the other walls
so again there's your needle and plastic cannula over the top
you get the flashback because you're in the vessel but then you go through one of the other walls and
now you can't feed your plastic cannula over again you've failed that cannulation attempt now what
we're not talking about is let's say you have an iv cannula insertion temp and you pass the needle
maybe a bit too superficially maybe it's to one side of it maybe it's underneath it somehow we're
not talking about that situation so the needle hasn't entered into the vein therefore the vein is
still intact the blood's still flowing there's no puncture sites on the vein which means that that
vein is still probably able to be accessed now first of all before we go into why i think you
can't rescue a failed cannulation temp if the vein has enough elastic tissue and it's thick enough
and it's able to clot well and just close that gap this is not for those circumstances now when
do those circumstance occur that's pretty much in pediatric patients or where you have really large
vessels and these vessels like central veins so imagine that you've got really nice large elastic
vein walls see if you do puncture that vessel you've got this hole there but fortunately the
vein is able to close it up and you don't have any problems the vein still works and that
often happens with central veins and to a less extent but still possible with pediatric veins
so what i'm going to say is that in that situation where you've got an adult patient and you're doing
peripheral iv access and your vein isn't one of those thick walled veins like a central vein so
it's peripheral and you've definitely gone into the vein so you've got flashback of blood into the
chamber i'm going to say it's just too high risk especially in quick care anesthetics emergency
situations to use that site of that vein you can still use the vein more proximally if you give
enough distance but it's just too risky to access that vein around where you first had the attempt
so why do i think this is too high risk so this is why imagine you've entered the vein like we showed
before and the cannula isn't in so you can't feed it off now you have a puncture site here in which
blood can flow out of so let's say you withdraw the cannula and try again to feed off that cannula
so you've re-angled the needle now you've pulled it out you've put it back in and so you've got
the needle there and let's say you get the cannula in this time so now you've fed the cannula through
and maybe it's working fine what you've got here is a problem now you've got a puncture site and
maybe even two puncture sides depending on how the failure occurred and now you're going to be
giving medicines that may go out and extravasate or leak out into the tissues so i'm going to say
that in the anesthesia and quick care situation this is a lot more high risk for example a lot of
the situations we're in are a lot more urgent for example you know you give an induction agent blood
pressure drops the heart rate changes depending on the surgery um or maybe there's a rapid change in
vital signs suddenly you need to give medications like metaraminol ephedrine even adrenaline that
need to get back to the heart and at the organs and vasculature immediately and so if you have any
question about whether this is extra fascinating you do not know and you're adding extra variables
into the system and you absolutely make sure that's not the case
one of the other reasons it's more toxic so a lot of the drugs we use for example thiopentone
muscle relaxants even opioids they're more toxic they have a very low narrow therapeutic range and
they can also cause damage to tissues so imagine in a thigh pentane extra fasciating into your
tissues can cause tissue necrosis same with other medications like metaraminol if you get into your
tissues causes intense phase of constriction and you don't want that that to happen imagine
opioids extraterrestrial opioids especially the stuff we use in anesthesia are so uh you know
potent so efficacious that you want to make sure that there's no deposits in your subcutaneous
tissue or your fat that might act later and you don't even know about it so again extra station
of these medications is really hazardous plus it may not actually be being delivered to the
organs that require it imagine that circumstance where you're running propofoltiva for a patient
who's got high risk of nausea vomiting and let's say that drip wasn't quite you weren't quite sure
is in and you salvaged it imagine all that profile leaking out into the tissues in one hand it's not
going to the patient keeping them asleep and on the other hand you'll be getting profile into the
tissues which again isn't ideal at all now one of those things that hopefully never happens to you
is that some medications are very painful in the skin so this includes profile rock uranium kefir
zone if this leaks out in the skin it can cause a lot of pain as well now finally often we have to
resuscitate with large volumes of fluid and this could be in the situation of anaphylaxis or rapid
blood loss or something that's happening in a trauma situation or with a high bleed risk surgery
and when we're giving that intraoperative fluid rapidly again you want to make sure that it's
going straight into the vein and back into the circulation so overall look my threshold for
being suspicious about a cannula is far higher than in other circumstances so to answer that
question would you ever try to rescue a failed iv cannulation attempt my answer is no for all
those reasons so thanks very much for watching any questions please write in the comments
below and yeah share with anyone who might be interested in this content see you next time
you