Performing an interscalene brachial plexus block using ultrasound
Learn how to perform an ultrasound-guided block and when this can be useful.
Today we'll explore the brachial plexus in a simple way—visually. Ultrasound can easily access this area, lending itself to safe and clinically effective nerve blocks. By the end of this video from our Ultrasound-Guided Nerve Block Masterclass, you'll understand the distribution of anesthesia provided and be able to determine the specific clinical situations when an interscalene brachial plexus block will be helpful.
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[00:00:00] The interscalene brachial plexus block is the bread and butter surgical anesthetic block of choice, for arm and shoulder procedures. Remarkably, in the past, this was commonly done without the assistance of ultrasound guidance. Today, we'll walk through the basics of performing this block with the assistance, thankfully for the patient,
[00:00:30] of an ultrasound machine and probe. Notice here the probe position. It is oriented at the base or the nape of the neck. Here's an even better example of where to place your probe. Notice the trachea here in the midline and the probe just lateral to it. This is the block I will almost always do in-plane. My technique is that I approach
[00:01:00] the interscalene plexus posteriorly, so from behind the patient. I will often place the ultrasound machine in front of the patient, so my eyes are not averted from my target. This is so I will not lose the needle tip at any time during this procedure. The first and best landmark to identify is the sharp point of the sternocleidomastoid muscle or SCM. You can see there that the muscle belly is enveloped
[00:01:30] by a bright white fascia and looks almost dagger-like in appearance. Once you locate this superficial sharp pointy muscle, look just beneath its tip, you'll find two distinctive muscle bellies separated by fascia. These two muscles are the anterior and the middle scalene muscle. They surround the brachial plexus in between them. As you see here, marked by the circles.
[00:02:00] This plexus constitutes the stoplight appearance, as it is commonly described. Watch now as the video starts and keep your eyes trained on the nerves. Notice here how the nerves appear darker than you may be accustomed to. Elsewhere in the body, nerves are bright white and hyperechoic. This is a phenomenon, we're really unsure
[00:02:30] of the reason why. The important thing is that you recognize that the nerves above the clavicle take on a darker appearance and almost look vessel-like. This is why using Doppler above the clavicles for any neck procedure is imperative. Here's a new image. Take a moment to get focused. Recognize that sharp SCM muscle at the top of the screen. I apologize if it's a bit cutoff but it's just up here and then direct your eyes just below
[00:03:00] its tip and you'll see your stoplight interscalene brachial plexus. Now, watch as the video plays and these circular structures become more apparent and dynamic to you. See here, your interscalene brachial plexus, on either side are anterior and middle scalene muscles.
[00:03:30] One last example. Notice here that the SCM is pointed in the other direction. We are on the left side of the neck. Also, notice how much shallower the scalene muscles appear. This is a skinnier person. The same anatomy holds true, however, as the brachial plexus remains snug between the two muscle bellies.
[00:04:00] Next step is to use Doppler. As I said, always use Doppler above the clavicles. First, identify the subclavian vessels and then move your Doppler gate or box up to your target zone between the scalene muscles. This will ensure that there are no major vessels in your way.
[00:04:30] Here, notice, there are no vessels in your way. You're safe for passage. Another example of a brachial plexus with Doppler, but here notice a very small arterial perforator that you'll want to avoid with your needle.
[00:05:00] The goal is to place the needle in a tissue space between the anterior and middle scalene muscles. Then, inject local anesthetic, until the spread around the brachial plexus is documented by your ultrasound. You will see the fascia peel away from the nerve bundles. The anesthetic will then spread along the brachial plexus inferiorly, surrounding your nerve roots appropriately.
[00:05:30] An effective block in this area gives you a large area of anesthesia from C3 to T1. It will, very occasionally, miss C8 through T1 distributions due to the lack of the anesthetic spread inferiorly, along that brachial plexus. Your interscalene brachial plexus block will, very occasionally, miss the distribution of nerve roots C8 and T1 so that’s ulnar distribution
[00:06:00] of the arm. This is due to the lack of spread of the anesthetic inferiorly, after injection. Remember that these roots are closest to the pleura. Often times gravity assists you and the fluid drops down and captures these roots. That's what you hope for. Very occasionally, however, these roots are not involved and you do miss a complete anesthetic result of the arm. Therefore, it is important to check, after
[00:06:30] the procedure, to ensure that the patient has appropriate anesthesia to these particular areas. So, why should I perform an interscalene brachial plexus block? Similar to the other blocks of the neck, the indications are fairly consistent. They involve arm procedures such as abscesses, laceration repairs, fracture reductions, shoulder dislocations is an excellent indication as well as
[00:07:00] elbow dislocations. In all of these instances, commonly a conscious sedation procedure will be done. However, now that you have the tools to do an interscalene block, you can use this instead. This is better for you and it's better for your patients.