The ultrasound-guided retroclavicular approach to infraclavicular brachial plexus block is useful when dense surgical anesthesia of the distal upper extremity is required. When anesthesia of the shoulder is required, the intrascalene approach to brachial plexus block is preferred as the retroclavicular approach provides spotty cutaneous anesthesia of the shoulder. Because the operator does not have to move the affected upper extremity to perform the retroclavicular approach to brachial plexus block, this technique is perfect when caring for patients in whom movement of the affected extremity would cause severe pain, for example, complex distal arm fractures and dislocations (Fig. 33.1). This approach is also suitable for placing a catheter for continuous infusion of local anesthetics due to the ease of catheter fixation.

In addition to having applications for surgical anesthesia, the retroclavicular approach to infraclavicular brachial plexus nerve block with local anesthetic can be used as a diagnostic tool when differential neural blockade is performed on an anatomic basis in the evaluation of upper extremity pain. If destruction of the brachial plexus is being considered, this technique can be used in a prognostic manner to indicate the degree of motor and sensory impairment that the patient may experience. The retroclavicular approach to infraclavicular brachial plexus nerve block with local anesthetic may be used for palliation in acute pain emergencies, including acute herpes zoster, brachial plexus neuritis, upper extremity trauma, and cancer pain, during the wait for pharmacologic, surgical, and antiblastic methods to take effect. The retroclavicular approach to infraclavicular brachial plexus nerve block is also useful as an alternative to stellate ganglion block for the treatment of reflex sympathetic dystrophy of the upper extremity.

Destruction of the brachial plexus via the infraclavicular approach is indicated for the palliation of cancer pain, including invasive tumors of the brachial plexus as well as tumors of the soft tissue and bone of the upper extremity. Because of the potential for intrathoracic hemorrhage, the interscalene approach to brachial plexus block should be used in patients who are receiving anticoagulant therapy only if the clinical situation indicates a favorable risk-to-benefit ratio.

The fibers that comprise the brachial plexus arise primarily from the fusion of the anterior rami of the C5, C6, C7, C8, and T1 spinal nerves. In some patients, there may also be a contribution of fibers from C4 to T2 spinal nerves. The nerves that make up the plexus exit the lateral aspect of the cervical spine and pass downward and laterally in conjunction with the subclavian artery. The nerves and artery run between the anterior scalene and middle scalene muscles, passing inferiorly behind the middle of the clavicle and above the top of the first rib to reach the axilla. After passing over the top of the first rib, the cords of the plexus continue their downward path in proximity to the subclavian artery and then the axillary artery (Fig. 33.2). In order to inject the brachial plexus at the infraclavicular level, the needle must traverse skin, subcutaneous tissue, and the pectoralis major and minor muscles (Fig. 33.3).

To perform ultrasound-guided retroclavicular approach to infraclavicular brachial plexus block, place the patient in the semirecumbent position with the ipsilateral arm slightly abducted to bring the artery and plexus closer to the skin facilitating ultrasound visualization. The clavicle on the affected side is identified by palpation, and an imaginary line is drawn between the midclavicle and the ipsilateral nipple as a guide to transducer placement (Fig. 33.4). After preliminary identification of the surface landmarks is completed, the skin is prepped with antiseptic solution and 16 mL of local anesthetic is drawn up in a 20-mL sterile syringe, with 40 to 80 mg of depot steroid added if the condition being treated is thought to have an inflammatory component.

A linear high-frequency ultrasound transducer is then placed over the previously identified imaginary line between the midclavicle and the ipsilateral nipple, and a survey scan is taken (Fig. 33.5). Placement of the transducer in this position will provide a short-axis view of the axillary artery as it passes under the clavicle as well as the cords of the brachial plexus. The artery will appear as a round pulsatile structure surrounded by the medial, lateral, and posterior cords of the brachial plexus (Fig. 33.6).