“Arterial Line Placement” by James DiNardo, MD, FAAP for OPENPediatrics

“Arterial Line Placement” by James DiNardo, MD, FAAP for OPENPediatrics


Arterial Line Placement, by Dr. James A. DiNardo. Hi, my name is Jim DiNardo. I am an associate
professor of anesthesia at Harvard Medical School and I’m one of the cardiac anesthesiologists
and cardiac ICU attendings here at Children’s Hospital Boston. We are going to be talking
about arterial pressure monitoring today, specifically placement of arterial pressure
monitoring catheters. Indications: The indications for placing an arterial line
include patients who require continuous blood pressure monitoring, such as those who: are
hemodynamically unstable, require vasoactive agents or active volume resuscitation, or
in whom non-invasive blood pressure monitoring is unreliable or unobtainable. Patients who
require significant respiratory support and need frequent lab sampling, including regular
arterial blood gases. But these indications must be weighed against the potential risks:
infection, trauma to the artery, potential thrombosis, hematoma. Contraindications: Some healthcare providers would refrain from
performing this procedure in patients with: infection at the insertion site, traumatic
injury proximal to the insertion site, inadequate collateral circulation of the extremity indicated
by a failed Allen’s test. Complications: The complications that you may observe include:
infection, trauma to the artery, thrombosis. Equipment: You will need the following equipment to perform
the procedure: arm board, tape, chlorhexadine prep solution, arterial catheter, guidewire
(we must make sure that the guidewire fits through the catheter), T-connector, sterile
occlusive dressing, sterile gloves, sterile towels, transducer system, saline flush. Techniques: Basically there are two types of techniques
for obtaining peripheral arterial access. The first is known as the slide-off, or thread-off
technique, where we place a catheter and needle system in the artery and then we actually,
once we obtain access, we slide the catheter off the needle into the artery. The other
technique is known as the through-and-through technique where we use a needle and catheter
system to actually intentionally go through both the anterior and posterior wall of the
artery and then we actually remove the needle from the catheter, pull the catheter back
to the point where just the catheter is in the artery – and we have obvious arterial
blood coming out of the catheter – and at that point, we insert a guidewire through
the catheter, which is then going to come out the end of this catheter and we use that
as a guide to thread the catheter off into the artery If you decide to use this thread-off technique
or slide-off technique, you are going to approach the artery at a much shallower angle than
you will if you intentionally do a through-and-through technique. And obviously the advantage of
approaching at a shallower angle is it is much more amenable once you get flow to threading
the catheter off into the artery. Whereas you can see in this technique, it’s very
unlikely that you are going to get a catheter to thread off a needle at a steep angle like
this. When you decide to go with this technique,
it’s important to remember that if you are unsuccessful at threading the catheter off,
it’s best to remove the catheter, hold pressure for a little bit and then reattempt again,
using that same technique if that’s the technique you are going to use, rather than
doing what people will often times try to do which is to convert this thread-off technique
to a through-and-through technique. And the problem with doing that is if you imagine
that I go at this shallow angle and attempt to pierce the posterior wall of this artery,
you can see that this is very different than this. And the difference is subtle but important.
At this shallow angle, if I go through the posterior wall of this artery, I am going
to raise a much bigger flap of intima on the posterior wall of this artery than I am if
I go through at this steep angle. And the problem with trying to convert this technique
to a through-and-through technique is that when I then go through-and-through and I pull
the catheter back, looking for blood and I am sitting right here, when I then go to place
the guidewire through this catheter, the guidewire is going to be directed directly at the area
here where I raised the intimal flap, and the likelihood that I am going to get the
guidewire to avoid the flap and track up this way is very small. It is important at the
outset to decide which technique you are going to use and stick to it. Placement sites: So when we think about the sites available
for blood pressure monitoring, we tend to think about peripheral sites versus central
sites. When we talk about peripheral sites, probably the most common peripheral site would
be the radial artery. And the reason that this is a popular choice is that it is easily
accessible, the pulse is generally easily palpated there. Even in most circumstances
of low cardiac output it is relatively easy to feel a radial artery pulse. And the other
is that the hand, which obviously is supplied by the radial artery, has good collateral
circulation from the artery on the other side of the arm, which is the ulnar artery. And
in fact the ulnar artery is bigger generally than the radial artery. So when we put a catheter
in the radial artery we are really potentially compromising the smaller of the two arteries
to the hand, which is supplied via the palmar arch from both the radial and ulnar artery. The other peripheral sites that we commonly
think of would be the dorsalis pedis artery here, on the dorsal aspect of the foot. And
the other would be the posterior tibial artery. And again, the reason that those two sites
are popular is that because there are two relatively major arteries to the foot, if
we catheterize one of the arteries we have good collateral flow from the other remaining
artery. The other peripheral site that is a potential area for arterial catheterization
is the brachial artery. Although in our experience that is probably the least popular site we
are going to talk about it, and the reason for that is the brachial artery is the sole
blood supply to the entire distal part of the arm, before the brachial divides into
the radial and ulnar arteries. So if we compromise the brachial artery, if it thrombosis, if
it goes into spasm, it is a relatively small artery that provides the total blood supply
to the arm and so as a consequence of that it’s not one of the most popular sites. Now, we mentioned that there are also central
sites, and the two most common central sites would be the femoral artery, obviously one
on either side, and the other would be the axillary artery. And when we think about central
sites, those are sites we generally reserve for patients where we are incapable of feeling
any distal pulse. So those would be patients who have profound shock states, either cardiogenic
or non-cardiogenic, or where they have had procedures or trauma to their extremities
that precludes placement of a peripheral line. The advantages of the femoral line obviously
are that it is a relatively big artery, so if we use a small catheter, even though it
is the sole blood supply to the leg, if we use a small catheter, there is going to be
flow around the catheter to supply the rest of the leg. And the same is true of the axillary
artery, although it’s the sole supply of blood to the distal arm, it is a relatively
large artery and as long as we use a relatively small catheter there will be flow around the
catheter through the axillary artery to the rest of the arm. When we are getting ready to cannulate the
different sites, and this obviously may vary from institution to institution and place
to place, when we talk about peripheral catheter placement, we consider that a clean but not
necessarily a sterile procedure. By that I mean if we were putting in a peripheral arterial
line we would use gloves, we would clean the area, we would use drapes prior to cannulation.
If we were cannulating a central site, specifically the femoral or axillary artery, we would consider
that a sterile procedure, and that would require, in addition to prepping, and draping, and
gloves, it would require gowning and a hat and a mask. Procedure: So we are going to walk through putting in
a radial arterial line and the first thing that we need to do is establish that there
is good collateral flow through the ulnar artery before we decide to put a catheter
into the radial artery. And there are a number of ways to assess the adequacy of collateral
flow but really the simplest is our patient has a pulse oximeter on their hand, and what
I am going to do is I am going to completely occlude the radial pulse with my fingers here
and then I am going to look at the pulse ox trace. And as long as the pulse oximeter trace
continues I know that there has to be good collateral flow through the ulnar artery.
So that even in the worst-case scenario, if I completely occluded the radial artery, this
child would continue to have flow to their entire hand through the ulnar artery. Point of Clarification: It is very important
to establish collateral flow before attempting arterial line placement, particularly when
using radial or ulnar cannulation sites. Collateral circulation to the hand can be verified by
performing an Allen Test, which involves checking the patient’s hand for perfusion while alternately
occluding the radial and ulnar arteries. We will now demonstrate how to perform an Allen
Test. While the patient clenches his or her fist, compress both the radial and ulnar arteries
for 30 seconds. If the patient is unable to cooperate, you will have to occlude the arteries
for a longer period of time and wait until the palm turns pale. Next, have the patient
open his or her fist, and the hand should be pale, meaning circulation has been obstructed.
Release pressure on only the radial artery, and observe the hand for the return of color,
indicating adequate blood flow through that artery. A normal result of an Allen test would
be the rapid return of normal pink color to the hand. If the hand does not return to normal
color quickly, this indicates abnormal flow through the tested artery. This test is then
repeated with the ulnar artery. Instead of visual assessment, blood flow can also be
measured using a pulse oximeter as was explained previously. So we are going to walk through putting a
radial arterial catheter in now. For optimal wrist positioning, place the patient’s arm
on a board with a roll of gauze pads underneath the dorsal part of the hand to create about
a 45 degree angle. This is important in order to provide comfort to the patient as well
as good exposure to the radial artery. We are going to assume for the sake of this
demonstration that our patient is well anesthetized and we are not really going to talk about
sedation or analgesia for placement of this catheter right now. So I have washed my hands
and put on a pair of sterile gloves, and we are now going to prepare the radial artery
for arterial cannulation. So what I am going to do is prep the skin
here and then drape it with the sterile towels. I am going to get the chloroprep organized
and I am prepping the skin. And I have left myself a really wide area here so I can see
the good part of the arm and the artery and I am prepping a nice, wide area. And then
I am going to take my towels and again I am going to do this in a way so that I leave
myself lots of room. There is no point in trying to do this through a really tiny little
hole. And I am going to use all four of these and make a nice little square so that I can
see what I am doing. Point of clarification. Remember, a time out
should be performed prior to any invasive procedure. So we’ve got our patient prepped and draped
here and what I am going to do is demonstrate now the method for using the slide-off technique
for putting this radial artery catheter in and you can see here that I have a catheter-over-a-needle
system here so this will just slide off. And this is a 22-gauge catheter. It is important to select the size of the
catheter based on the size of the patient. 24 gauge catheters are used for infants, 22
gauge for toddlers, 22 to 20 gauge for small children, and 20 to 18 gauge for larger children
and adults. And remember as we said earlier for the technique
where we slide the catheter off, we are going to go at a very shallow angle so I am going
to be at an angle like this as opposed to an angle like this if I were going to intentionally
go through-and-through the artery. And you can image how in order to be able to thread
this off, going at this shallow angle like this, it will be much more likely that I will
be able to thread the catheter off. So what I am going to do is feel the pulse
here and orient myself with the catheter at a relatively flat angle and then I am going
to be looking for blood return in the top of this catheter. Some people will flush the
catheter with saline as a way of enhancing the ability to see a flash a blood. You can
see that there is a little flash of blood there in the hub of the catheter, and now
what I am going to do is that I am still going to continue to have flow here so I ought to
be able to thread this catheter off right into the artery which we have done. And then
I have my connector, which I have clamped here and I also have a little cap on the end
of it. And what I am going to do is take the needle out now and hook this up to my connector.
And you can see that I have the free return of blood there. Please note that when connecting the T connector
to the transducer system, it is important to ensure that no air bubble is introduced. So I am hooked up now. And I can then stabilize
this with my occlusive dressing like so. And then what I can do now that I have control
of this is unclip this and I’ll have blood coming back through my connector to here and
now we will be ready to hook this to the transducer system. The use of a heparinized or unheparinized
saline flush is necessary to ensure that good arterial blood flow can be drawn back and
flushed through the T-connector system. Assessment and Monitoring: It is important to assess the patient’s
perfusion of the distal extremity and to monitor for signs of infection at the insertion site.
You should also closely be watching the morphology of the arterial line tracing and blood pressure
values on the monitor. Documentation: Following arterial line placement, you should
document the following information in the patient’s medical record: indication for
procedure, date and time of procedure, site of placement, size of catheter used, number
and location of all attempts. That concludes our video on Arterial Line
Placement. Please help us improve the content by providing us with some feedback. What did or didn’t you like about this video? Was the content too simple, just right, or too difficult? Was the length too short, just right, or too long? Any additional comments? You can either click the “start a new discussion” button and type in feedback or send us an email at [email protected] Note, feeback is not required to complete this activity in the guided learning pathway.

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