Radial Access Made Easy: Try Ultrasound Guidance

I saw an ad on television made by SonoSite, a maker of portable echo machines. The ad showed a dynamic, pretty woman doctor running around “seeing inside” everything (by ultrasound imaging, of course) she examined (almost). I was entertained, but also, impressed. It is true that portable and small hand-held ultrasound (US) imaging units have made their way into critical care medicine in the ICUs, emergency rooms, and into early years of medical school, where students are learning advanced techniques of ultrasound to validate physical exams. Ultrasound imaging has been and continues to be a major advance in all fields of medicine. And after my experience with ultrasound for the cath lab, I have become a true believer, especially for radial access. This insight into the use of US in the lab would not have occurred were it not for my younger colleague, Dr. Arnold Seto. Dr. Seto’s background in critical care medicine and his cardiology fellowship training made him an excellent teacher of this technique and brought this practical approach to our radial procedures. I am sure you will find Dr. Seto’s article on ultrasound-facilitated radial access in this issue of CLD fascinating and helpful.

Most common problem with the radial approach

In beginning our radial program, teaching the fellows how to get radial access was the most common problem with the procedure. It was apparent that this was a significant point of difficulty for some. This fact is borne out in the literature, where more than 40% of all problems with the radial cath technique involve some issue with wrist access (initial puncture, spasm, failure to pass wire for some reason, etc.). With the use of ultrasound, the fellow can see the artery and the needle tip, and greatly shorten access time learning.

Why is access by manual palpation at times so difficult?

The radial artery is, on average, only 2.5-3 mm in diameter. Because of the nerve density on the fingertips, one can only resolve distances on the skin to within 2 mm at best. That is, one cannot distinguish a pulse within 2-3 mm with precision. In addition, the sensitivity of an individual’s tactile discriminatory spatial resolution varies greatly. We also know from experience that palpation of the radial artery does not always put the needle over the middle of the artery. Operators must take time to carefully locate the artery over a small area (about the size of a dime) over the pulse, stabilize it as best they can, advance the needle and hope it enters the artery, verifying entry by seeing the blood flash back. Most experienced operators have mastered their proprioceptive potential with practice, but there are many patients in whom 4, 5, or more needle passages and attempts to enter the artery still fail. Moreover, despite excellent operator technique, access can still be difficult in two types of patients: those with large, thick wrists and those with very mobile, rolling arteries.

Use of ultrasound is not an admission of an operator’s technical weakness

As an older operator with some experience, I had initially thought that using ultrasound imaging in the cath lab to help find the artery was unnecessary, but subconsciously, my decision to use ultrasound was an affront to my machismo of vascular access. “I can stick anything,” I thought. Wrong. There were cases of radial access that drove me to the edge of my patience. At this point and despite my mindset, Dr. Seto showed me how ultrasound imaging for access can really help (Figure 1). His article in this issue illustrates how we use US for radial access. After trying US a couple of times, I became adept and a strong believer. We now recognize that this is one of the best ways for new operators to shorten the time for radial artery access and for all operators get it right on one stick. I have shortened my access time in several situations and find that the fellows are learning the technique quickly (Figure 2).

US access beyond the radial artery

US can easily be used in the cath lab for both radial and femoral access (see the Faust study). Some experienced operators will say US is totally unnecessary, because they never have a problem. Of course they and you know this statement is not true. Every operator has had a problem with vascular access at one time or another. For femoral access, especially in the high body mass index (BMI) patients, finding the femoral artery can be a daunting undertaking. Obviously, in these patients, the better access is radial, but even then, with extra adipose tissue in the arm, the wrist access by traditional palpation may be challenging and involve the ‘hunt and peck’ technique, to the frustration of everyone. Ultrasound can help greatly in both situations. 

Of interest, Dr. Seto is conducting a randomized study to compare the time to access, number of needle sticks, and crossover to ultrasound for experienced operators using the traditional manual versus US-guided radial access. While this study ultimately may or may not demonstrate a difference between methods, it will certainly identify a group of patients in whom the manual method is worse than ultrasound-guided access.  Where I think this technique will be of even greater value is in teaching new fellows and operators new to the radial approach a way to overcome any difficulty with radial access. 

With ultrasound imaging, the operator can see the artery and the needle enter the artery as it is advanced through the skin toward the artery. Moving the needle up and down shows one where the needle tip is relative to the artery. The operator can easily redirect the tip to the center of the artery. It takes just a couple of cases to demonstrate how easy this is. In those patients with faint radial pulses, thick wrists and deep arteries, I am impressed with how ultrasound facilitates my time to access.

Ultrasound is also helpful for venous access in the arm. While superficial venous access forearm veins can be cannulated with an Angiocath, some patients have no visible arm veins. This problem is especially true in the large BMI patients. By putting the ultrasound probe over the elbow crease, you can see the brachial artery and the adjacent brachial vein. Pressure with the US probe on the skin compresses the tissue and verifies the vein image, which collapses with pressure while the artery pulsation and patency persists. Using the ultrasound with its visual cues permits easy access of the Angiocath needle system into the vein, avoiding accidental artery puncture. For other operators wishing to access the internal jugular vein, the use of ultrasound has been the standard of care in the ICU/CCU settings for many years. 

Bottom line

I like ultrasound for radial access. It is quick and easy. Although manual palpation is the most widely used and highly successful method, try US for routine cases to gain experience for the hard cases. Then when you have that particularly challenging radial artery, the ultrasound approach will really demonstrate its worth. Finally, I think that a portable ultrasound machine in today’s cath lab should be a mandatory piece of equipment, given our need for improving vascular access.

Reference

1. Seto AH, Abu-Fadel MS, Sparling JM, Zacharias SJ, Daly TS, Harrison AT, Suh WM, Vera JA, Astonce CE, Winters RJ, Patel PM, Hennebry TA, Kern MJ.  Real-time ultrasound guidance facilitates femoral arterial access and reduces vascular complications: FAUST (Femoral Arterial Access With Ultrasound Trial).  J Am Coll Cardiol Intv 2010;3: 751-758.