Cadaver Surface and Ultrasound Guided Anatomy of Nerve Blocks in Anesthesia Program
We'll be talking about the interscaleneblock. The analgesia of the brachial plexus, which enervates the arms, is an example ofa major nerve block. That is because two or more nerves are blocked that supply a largearea. Types of surgeries that would benefit from interscalene block include the shoulder,arm, and forearm procedures. Injection at the interscalene level will block dermatomesC5 through C7 intensely, and dermatomes C8 through T1 less intensely. The interscalene groove lies at the cricoidcartilage, the level of the cricoid cartilage. It's important to find the sternal notchand trace it over to the clavicle, and then
outline the sternocleidomastoid muscle. Itis 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 rootsof C5 through C7. There are several maneuvers that can accentuate the line marks while thepatient is lying supine. First you have the patient turn their head to the contralateralside. This is when you will be able to see the external jugular vein cross the interscalenegroove 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 theneck and makes the identification of the scalene muscles easier. Some complications that occurinclude incidental block of the phrenic nerve, recurrent laryngeal nerve, and stellate gangliondue to close proximity. Dyspnea may occur from the nerve, the phrenic nerve, causing hoarseness, andfrom the recurrent laryngeal nerve. Since the area is very vascular, there ispotential for inadvertent intravascular injection. First, this is the clavicle. Here is the sternocleidomastoid muscle. Common carotid.
Internal jugular. External jugular. Anterior scalene muscle. And middle scalenemuscle. And the three trunks for the brachial plexus: superior, middle, inferior. This is the left arm, and the branches ofthe 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 interscaleneblock. 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, andShane'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 betweenthe anterior scalene muscle and the middle scalene muscle here, and here's our nervebundle, right in there. Here we have the surface anatomy for a femoralblock. 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 femoralvein, 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 upperthigh area, where we will be performing our