Supraclavicular Nerve Block Technique
- Author: Alma N Juels, MD; Chief Editor: Meda Raghavendra (Raghu), MD more...
The block is best performed as an ultrasound-guided block. It has been performed blindly, with a Doppler used to guide the needle around the subclavian artery, with a nerve stimulator and ultrasound/nerve stimulator combination. Due to the high risk of a pneumothorax, the supraclavicular block was no longer performed by most anesthesiologists until the resurgence of the ultrasound as a guide to regional anesthesia.
Supraclavicular Nerve Block
Landmark: Clavicle and subclavian artery
Start at the sternocleidomastoid muscle right above the clavicle. The probe is parallel to the clavicle, moved laterally toward the midpoint of the clavicle; the probe should be in the supraclavicular fossa above the clavicle. The patient is placed semi-sitting; raise the head of the bed about 45° and have the patient turn their head in the opposite direction (see image below).
At this location, the subclavian artery is seen beating above the first rib; it cannot be compressed as opposed to the vein. Sometimes the subclavian artery can be palpated. Pleura are seen on each side of the rib. The rib is bright (see the image below). The provider can stand at the patient’s side, the same side that is being blocked or at the patients head.
The brachial plexus is lateral to the subclavian artery. Once the subclavian artery is visualized, explore the area superficial and lateral until the plexus is seen. It has the characteristic honeycomb appearance. The view can be of multiple nerves or just 2. It helps to rock the probe cephalad to caudal, lateral to medial, to find the best plane to visualize the most nerves from the plexus and get a good quality picture.
The needle is inserted on the lateral side of the probe since the plexus is located lateral to the subclavian artery. The entrance point is 1 cm away from the probe to decrease the angle of insertion, and it is moved from lateral to medial. The needle is placed in the long axis, in plane to the probe, and should be visualized at all times. This is especially important for this block since the needle can cause a pneumothorax if not visualized at all times.
To confirm lung parenchyma, ask the patient to take a deep breath; the characteristic multiple parallel lines of the pleura layers move, and the change in lung appearance occurs. The needle is advanced under direct visualization toward the angle formed by the first rib and the subclavian. A small amount of local anesthetic solution is injected to confirm the location of the needle tip; this can be done while slowly advancing the needle.
The injected volume gently expands the connective tissue surrounding the nerves, which is called hydro dissection. This allows a clear path for the needle, decreasing the chance of nerve damage of the nerves by the needle. The clinician should see the spread of local anesthetic in the angle between the first rib and the subclavian artery. Color Doppler can be done to confirm that the artery is visualized if any doubt exists. The subclavian vein is medial and superficial to the artery and is compressible. Remember to aspirate every 3-5 mL during injection to prevent vascular injection.
Place the patient supine, with the head of the bed at 30°. The patient’s head is turned away from the side being blocked, same as the ultrasound block. ThesShoulder is down, the upper arm by the patient’s side, flexed at the elbow and wrist supinated on patients abdomen. Identify the clavicular head of the sternocleidomastoid (SCM) muscle at its insertion into the clavicle. The area medial to this is considered the "unsafe" zone and is high risk of pneumothorax; the lateral area is safer.
The trunks are short and run very steep above the clavicle, which does not give a large area to work with. The area is about 2.5 cm (1 inch) lateral from the insertion of the SCM to the clavicle (usually at the midpoint of the clavicle). The brachial plexus can usually be palpated at this point as a bump or groove called the interscalene groove. It can be a little medial or lateral to this point but not too far. Where the interscalene groove is palpated is where the needle is placed.
The needle is inserted anteroposterior with a 30° caudal orientation. Advance slowly up to 1.5 cm depending on the amount of subcutaneous tissue. Usually a twitch of the shoulder is seen as the needle approaches the front of the plexus. The needle is advanced caudal, parallel to the midline, perpendicular to the clavicle, at a 10° angle. As the needle is advanced after the shoulder twitch, the pectoralis and triceps will twitch, then the wrist and finger. This corresponds to the upper trunk, middle truck, then the lower trunk. Once the desired twitch is obtained at 1 mA, decrease the amplitude to 0.4-0.5 mA and make sure the desired twitch is still present. The goal is isolated twitch of the fingers only. If the desired twitch is not obtained redirect the needle, do not advance the needle more than 2 cm caudally.