We’ll be talking about the interscalene block. The analgesia of the brachial plexus, which enervates the arms, is an example of a major nerve block. That is because two or more nerves are blocked that supply a large area. Types of surgeries that would benefit from interscalene block include the shoulder, arm, and forearm procedures. Injection at the interscalene level will block dermatomes C5 through C7 intensely, and dermatomes C8 through T1 less intensely. The interscalene groove lies at the cricoid cartilage, the level of the cricoid cartilage. It’s important to find the sternal notch and trace it over to the clavicle, and then.
Outline the sternocleidomastoid muscle. It is recommended that you also outline your carotid artery, internal jugular, and external jugular vein. You will also see the anterior scalene muscle, little scalene muscle, and the nerve roots of C5 through C7. There are several maneuvers that can accentuate the line marks while the patient is lying supine. First you have the patient turn their head to the contralateral side. This is when you will be able to see the external jugular vein cross the interscalene groove at the level of the cricoid cartilage.
This also tenses the sternocleidomastoid muscle. You may also ask the patient to reach to the ipsilateral knee. This maneuver flattens the neck and makes the identification of the scalene muscles easier. Some complications that occur include incidental block of the phrenic nerve, recurrent laryngeal nerve, and stellate ganglion due to close proximity. Dyspnea may occur from the nerve, the phrenic nerve, causing hoarseness, and from the recurrent laryngeal nerve. Since the area is very vascular, there is potential for inadvertent intravascular injection. First, this is the clavicle. Here is the sternocleidomastoid muscle.
Cadaver Surface and Ultrasound Guided Anatomy of Nerve Blocks in Anesthesia Program
Common carotid. Internal jugular. External jugular. Anterior scalene muscle. And middle scalene muscle. And the three trunks for the brachial plexus superior, middle, inferior. This is the left arm, and the branches of the brachial plexus are the musculocutaneous nerve, the median nerve, the ulnar nerve, the radial nerve, and the axillary nerve. Here we have an ultrasound view of the interscalene block. We are looking at the right side of the neck. This is medial, and this side of the ultrasound is lateral. We have the carotid artery here, we have the right IJ here, and Shane’s doing a Valsalva maneuver right now.
We have the anterior scalene muscle here, the middle scalene muscle here, and our sternocleidomastoid on top. The nerve bundle is located between the anterior scalene muscle and the middle scalene muscle here, and here’s our nerve bundle, right in there. Here we have the surface anatomy for a femoral block. First you want to identify the anterior superior iliac spine and the pubic tubercle, and draw a line connecting these structures. This is the inguinal ligament. Midline on the inguinal ligament, you’ll palpate to find the femoral pulse. And using.
Your VAN acronym, you can see the femoral vein, femoral artery, and femoral nerve. To find the femoral nerve from the femoral pulse, you’ll go two centimeters distal and two centimeters lateral. I will use the width of my finger to approximate this distance. Two centimeters distal, two centimeters lateral, and you will end up right over the femoral nerve. This is your injection point. Here we have a cadaver dissection of our upper thigh area, where we will be performing our femoral nerve block. Landmarks that you are looking for, for the femoral nerve block,.
Are your anterior superior iliac spine and your pubic tubercle. You’ll draw a line connecting these two structures, I have a dotted line here, to display that. When you’re doing the block, you’ll palpate for the femoral artery pulse along that line. It’s approximately midline. Once you’ve located the pulse, you’ll move two centimeters distal and two centimeters lateral for your injection site. You can just approximate that with a finger, your index finger. Two centimeters distal, two centimeters lateral, and as you can see, we’re right over the femoral nerve. As you.
Can see, if you use your VAN acronym, which is vein, artery, nerve, from medial to lateral we have the femoral vein, femoral artery, and femoral nerve. One of the possible complications to this block, which is very rare, is intravascular injection, because of the close proximity of the femoral nerve to the femoral artery. Okay, you are looking at the view of the femoral nerve block. On our screen, we have medial and lateral. You can see the femoral vein, which is compressible, and the femoral artery. And if we scan down, we can see it bifurcate.
And lateral to the femoral artery is the femoral nerve complex. It is below the fascia lata and the fascia illiaca. So below there is the femoral artery and femoral nerve complex. Here we’re doing the surface anatomy of a popliteal block. I have drawn out the popliteal fossa, starting with the tendon of the semitendinosus and then the tendon of the biceps femoris at the popliteal crease, drew a flat line in the middle. Measured, it was actually 6 centimeters, so at 3 centimeters I measured, drew a line, and then outlined the popliteal.
Fossa. I then bifurcated the triangle and then measured up 5 centimeters, and went lateral one centimeter. Popliteal injection on surface anatomy generally will be right here, inside your popliteal triangle. Here we are looking at the posterior left leg. The sciatic nerve splits into the tibial nerve and the common peroneal nerve in the popliteal fossa. The nerves are superficial to the popliteal artery and vein. We are doing the ultrasound of the popliteal block. Currently, we’re at the popliteal crease, and we are medial and lateral. We have our semitendinosus muscle, our semimembranosus muscle, and our biceps.
Femoris muscle. We have the popliteal vein, which is compressible, and then our popliteal artery, that you can see here pulsating. We then have our common peroneal nerve, and then also our tibial nerve. As we scan the leg, they are coming together to form our sciatic nerve. Right before the bifurcation is going to be the ideal site for your popliteal nerve block. All right, I just want to point out some landmarks here for placing an epiduralspinal, that we have our coccyx, our sacrum, and then we have our fifth lumbar, our fourth, third,.
Second, and first lumbar vertebrae. And also here we have our iliac crest on both sides, and as you can see here, our iliac crest comes approximately at L4. Now this imaginary line right here is called the intercristal line or the Tuffier’s line. These iliac crest are going to be the landmarks that you’re actually going to be feeling on your patient to feel for your L4 lumbar. Now placing an epidural or a spinal, you can go below or above the L4. This is generally. Now, the patient is generally going to be sitting in.
An upright position, bent over, opening up the access to get to inside the vertebrae or also on a lateral side, hunching in more of the fetal position. As I said here, just pointing over again, you have the iliac crest coming in line here with L4, placing an epidural or a spinal below L4 or above L4. Here I’m going to show you the proper positioning here for placing an epidural andor spinal. You’ll want to have the bare back exposed here, and you’ll have the patient that’ll want to get into a C position that’s going to help open up the spinal processes. So the.
Patient here will go and almost push up against my hand here, forming a backwards C. Now I’ve predrawn out right here the iliac crest. The iliac crests form an imaginary line, intercristal line, and at the intercristal line is going to be your L4 spinal process. And I’ve already premarked here the L5, L3, and L2. So here are our spaces here between our spinal processes, between L2 and L3, L3 and L4, L4 and L5, and L5 and sacrum. Epidurals and spinals can be placed anywhere in between these spaces here,.
Generally, as your conus medullaris of your spinal cord will typically land between your L1 space. So as I said before, typical placements here are going to be between L2, L3 for spinals and epidurals, and between your L3, L4 or even going down to your L4, L5. But typically, you could actually put an epidural anywhere along the entire continuum of the spinal column, but if you ever have to do a spinal, do not go above your L2, as you could hit that conus medullaris. What I’m holding here is a lumbar vertebra. As you can see, right inside here is going.
To be the vertebral foramen. This is where the spinal column is going to be sitting, the spinal cord will be sitting right in the vertebral foramen. A laminectomy was performed here on this cadaver here to reveal our sites here for inserting an epidural, spinal, andor doing a spinal tap for withdrawing cerebral spinal fluid here. I just want to point out here, after the laminectomy is done, we have the dura mater. The dura mater is what surrounds the spinal cord and withholds cerebral spinal fluid. The spinal cord right here actually floats within that.
Cerebral spinal fluid, and the spinal cord comes from your medulla oblongata, all the way down to approximately at L2. At the end of L2, it becomes your conus medullaris. The conus medullaris is actually the coneshaped process of the spinal cord and the continuation on with the filum terminale internum, which will then anchor itself into the sacral hiatus at the end of the dura mater sac. Now also, coming off the spinal cord here is going to be your cauda equina, also known as horsetail. As you can see here, these tail fibers coming off, these are going.
To originate off the spinal cord at approximately L1 all the way down to the S5, your sacral, your fifth sacral is where they’re going to go off. Now, some may wonder, when we do a spinal, aren’t we going to end up making contact with the conus medullaris, and could form what is, say, a total spinal, as if you injected directly into the spinal cord. Well, these, actually the equina, will be freefloating within the spinal column here, so when you insert the needle, they should actually theoretically move out of the way. Now as you can see here,.
The dura mater, in order to do a spinal you actually have to penetrate the dura mater, but now in doing an epidural, you are actually instilling medication above this dura mater. And as you can see here, this is very, very thin, so the precise distance of performing an epidural versus a spinal is a very, very small distance. And once again, we have our spinal cord, the conus medullaris, and then the cauda equina, all of the spinal cord. Now a great acronym to actually remember for the placements of the needle for an epiduralspinal.
Is SSSILDA. These are the layers, or levels, that you’re going to be going through to place your epiduralspinal. SSSILDA. S for skin. S for subcutaneous layers. So here we have our skin layer, which has been removed, and then you enter the subcutaneous fatty layer. The next, third S is your supraspinous ligament. So you can remark right here, which actually is going to be the ligament that actually traverses across the tip of your spinous process. Your next letter, I, is going to be your interspinous ligament, which will.
Actually be a ligament that connects the spinous processes to the superior and inferior together. And this is if you’re doing a midline approach. And now your next layer is going to be your ligamentum flavum, which is actually going to, as soon as you break through that, is going to be your potential epidural space. That is where you are going to be placing your epidural drug, andor epidural catheter. The next level that you’re going to break through, which I pointed out before, is your dura mater. Now the dura mater is what, inside,.
Is going to house your cerebral spinal fluid. And then your next layer is going to be the arachnoid mater. The arachnoid mater is what actually surrounds your spinal cord, spinal process, which is where you’re going to be having, giving your spinal. Now just remember, spinals are not given directly into the spinal cord, as that will give a total spinal and can be very, very detrimental to your patient. So always avoid any injection directly into the spinal cord. And this way, if you’re doing any spinal, you want to be going below L2,.
As the conus medullaris is, in general, housed at L2. So by going at between above and below L3, L4, and L5, you should avoid any total spinals. Okay, so here we are showing a midline approach of a sagittal plane of the lower back. And I just want to point out here that we actually have a spinal process here, and a spinal process here. So for us to be placing an epidural andor spinal, we actually have our interspinous here, in between our two spinal processes. So this is a great advantage you can use in.