Arterial Line Placement with Ultrasound

 Kalemegdan in Belgrade - photo by JoAnn Sturman

Four observations follow regarding the placement of arterial lines with ultrasound guidance.  Dr. Ikemiya presents a thorough discussion of the subject, which is supported by comments from Drs. Van Putten, Radich, and Wiggins.

Kenneth Ikemiya, M.D.

I use the ultrasound on patients with 1) weak pulse 2) known severe PVD, or 3) one failed attempt using fingers and tactile sense.  In other words, I have a low threshold for asking for the Sonosite. After I prep the wrist and lower forearm, I do a quick scan of the radial artery as travels through the forearm.  It's remarkable how in just a few millimeters, there can be a significant change in the diameter of the vessel. I place the probe over the artery at the point I want to enter the vessel with the needle. I insert the needle out of plane about 1 cm distal from the probe at 45 degrees.  Be careful on how much pressure you use on the probe, so you don't compress the artery. Advance the needle till you see it enter the artery at its widest point. There will be a flash. I try to only enter the anterior wall, then thread the wire.  Finally I slide the entire ensemble in to the hub, then pull out the needle and wire. If you try and just advance the catheter, it can distort the tip of the catheter and leads to a dampened tracing. If the wire won't pass, then I go through the artery, pull out the needle, and withdraw the catheter till you get good flow. Then try and pass the wire.

The radial artery is designed to have redundancy at the wrist to allow for flexion and extension of the joint. Older patients may have soft, redundant tissue at the wrist as well.  I always hyper-extend the thumb AND put distal traction to make the skin at the wrist taught and straighten the artery. I go above the most proximal wrist crease as the artery tends to straighten more proximally.  Again, I enter the wrist 45 degrees in one plane and perpendicular to the skin in the other plane. This helps keep a calcified artery from dancing away from the needle.

Finally, I don't suture in the radial line. I feel in older patients especially, the suture can pull through their skin. It also serves as a hinge point where the catheter can slide in and out of the skin and/or artery. I use the IV Tegederm which securely fixes the catheter and provides visualization of the site.

Potala - photo by JoAnn Sturman

Cliff Van Putten, M.D.
 
Despite a seemingly proper orientation between catheter and artery, lack of blood return under ultrasound guidance is probably due to unrecognized penetration of the artery.  This misinterpretation can occur in the out of plane view, since the observer may not be visualizing the catheter tip, but rather, a baloney slice farther up the shaft of the needle.

Monk in Luang Prabang - photo by JoAnn Sturman

Ned Radich, M.D.
 
I typically do get a flashback with a-line placement.  I go out of plane about 1 cm from the entry point at the same angle one would with conventional a-line placement.  I think the problem is that one tends to focus on the screen and goes through the artery before realizing it; the radial artery is typically quite superficial. I adjust my technique to use ultrasound to locate artery, then watch the catheter as I'm advancing it past the skin (just as we've done in past). If I do not get flash, I use ultrasound to discern where my needle is and make necessary adjustment.

Great Wall - photo by JoAnn Sturman

Mike Wiggins, M.D.

Often one compresses the artery with the needle; especially if it's calcified. With ultrasound it appears the angle of entry to the artery is perpendicular, but it obviously is not.  One trick is to puncture it with a quick stab vs. a slow penetration. 

I view a cross section of the artery (typically more proximal than the usual non U/S spot, as the artery is slightly deeper and larger); the needle entry point is a few mm from the probe at about a 45 degree angle. I look at the needle tip as it pushes on the arterial wall and adjust as necessary to make it a straight shot. I do a quick jab to puncture the thick wall and perform the usual maneuvers. I always look at the screen just as I would with a peripheral nerve block.