Infraclavicular Brachial Plexus Block

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Ultrasound-guided Infraclavicular Brachial Plexus Block
Infraclavicular block has become a popular technique for producing anesthesia and postoperative analgesia of the upper limb. It has the advantage of blocking all three cords of the brachial plexus whilst reducing the risk of pneumothorax associated with supraclavicular block. Catheter placement is facilitated by the relative ease of insertion and fixation of the catheter to the anterior chest wall.

Anatomy
At the Infraclavicular level the cords of the brachial plexus are arranged around the 2nd part of the axillary artery. Immediately medial to the coracoid process, the lateral cord of the plexus lies superior and lateral, the posterior cord lies posterior and the medial cord lies posterior and medial to the axillary artery.
Anterior to the brachial plexus are the pectoralis major and minor muscles. Posterior to the brachial plexus in this region is the scapula. The axillary vein is commonly located caudal and medial to the axillary artery.

Patient positioning
Position the patient supine with the head turned approximately 45 degrees to the contra lateral side
Equipment
A high frequency (10-12MHz) or small curved 8MHz probe
Depth 3-5cm
50- 100mm short beveled needle
Nerve stimulator
Sterile preparation kit, syringes and local anaesthetic

Ultrasound scanning technique
The probe is placed below the clavicle laterally at the level of coracoid process। Scan from below clavicle and move medial to lateral. Top of the image you will see the pectoralis Major, then pectoralis minor. Deeper to muscle the axillary vein and artery are seen. The vein is caudal to the artery. You can visualize Hyper echoic nerve structures cephalad, posterior and caudal to the axillary artery.

Needling technique
The ultrasound-guided technique uses a needle insertion point just inferior to the clavicle and 2cm medial to the coracoid process. The tip is advanced under direct vision to the supero-lateral aspect of the 2nd part of the axillary artery and at this point, if desired, a nerve stimulator can be used to confirm distal stimulation in the forearm or hand. Usually stimulation of the lateral cord can be obtained at the 9 o’clock position and the posterior cord at the 6 o’clock position on the artery. The medial cord between 1’o clock to 4’o clock position. With this technique obtaining distal muscle stimulation is not essential because successful block is usually associated with spread of local anesthetic immediately superior and posterior to the 2nd part of the axillary artery. If spread of injectate is observed anterior to the artery or proximal muscle stimulation is obtained then the needle should be repositioned posterior to the artery and posterior spread of injectate confirmed.

Tips
Hyperechoic density posterior to the axillary artery can be due to “acoustic enhancement”, an artifact generated when beam crosses a vessel with little acoustic impedance. Angle (tilt) the transducer slightly in the parasagittal plane to check if this hyperechoic structure stays in the same location. If it does not, this is not likely to be a nerve structure. The usual risks of infraclavicular block including intravascular injection, pleural or nerve injury are also possible with an ultrasound-guided approach. It is important to be able to visualize the tip of the needle as it is advanced otherwise injury can occur without knowledge of the practitioner. There is a wide variety of Variations in the location of plexus around the artery. In doubt we can use nerve stimulator for confirmation.