The authors’ preferred needle trajectory is from lateral to medial (through the middle scalene muscle) using an in-plane technique (Fig. 29.1a). It is sometimes necessary to adopt a brief steep initial needle trajectory in order to pierce the prevertebral layer of the deep cervical fascia that overlies the middle scalene muscle. Once this “pop” has been felt, the needle should be flattened out and advanced toward the plexus. In the authors’ experience ultrasound guidance alone is adequate and nerve stimulator guidance is not usually required. The needle is advanced, and a second “pop” may be felt as the needle tip passes through the anterior border of the middle scalene muscle and the plexus. Incremental injection of 1–2 mL of local anesthetic can be used at this point to hydrodissect the plane between the muscles and plexus. Care should be taken to avoid local anesthetic being deposited inside the belly of the middle scalene muscle. Injection of local anesthetic on one side of the trunks at the C5–C7 level should be sufficient.

The authors’ preferred needle trajectory is similar to single-injection techniques except the ultrasound transducer is rotated slightly and translated so that the needle entry point is positioned more cephalad and posterior taking the catheter skin entry point away from the surgical site. The needle trajectory now has a slight caudad angulation. Separating the needle skin entry point increases ease of needle visualization and also creates a tunnel for the catheter, reducing risk of dislodgement. Figure 29.2 demonstrates a patient positioned on their side for an interscalene catheter placement using a posterior in-plane approach. Figure 29.3a demonstrates the needle trajectory with needle at muscle–plexus interface and Fig. 29.3b the post-injection displacement of the middle scalene muscle. The sonogram in Fig. 29.3c shows the catheter following removal of needle. Note that the rotation of the probe may distort the image such that the trunks of the brachial plexus are less well demarcated and the sternocleidomastoid and middle scalene muscles appear elongated. The catheter tip position should be determined before commencing a local anesthetic infusion.

The ED₉₅ required to achieve postoperative analgesia for C7 interscalene brachial plexus anesthesia has been calculated to be 3.6 mL of ropivacaine 0.75 % [18]. In routine practice, 10–15 mL of local anesthetic such as ropivacaine 0.2–0.75 % is appropriate. The exact concentration will depend on patient factors, the purpose of the block (analgesia or anesthesia), and if a catheter technique is used. If a catheter is placed, the initial dose can be reduced and additional local anesthetic can be injected through the catheter. An infusion of ropivacaine 0.2 % 4–10 mL/h is used for postoperative analgesia.

The expected distribution of anesthesia following interscalene brachial plexus block is shown in Fig. 29.4 [19].

Phrenic nerve block occurs commonly following both interscalene and supraclavicular approaches to the brachial plexus. The proposed mechanism is that local anesthetic spreads across the anterior surface of the anterior scalene muscle and involves the phrenic nerve and/or there is cephalad spread toward C4. However, other mechanisms have been proposed including the existence of variations in the origin of the phrenic nerve from the brachial plexus itself [20, 21]. Usually phrenic nerve block is not of concern and management comprises patient reassurance. In patients with reduced pulmonary reserve, phrenic nerve block may be of concern; therefore strategies have been suggested to reduce the risk of phrenic nerve blockade. These strategies include dose reduction, using a more caudal target (C7), using ultrasound guidance, or avoiding interscalene block [22]. Following both interscalene and supraclavicular brachial plexus blockade, ultrasound guidance is associated with a reduced incidence of phrenic nerve paresis compared to nerve stimulator-guided techniques [23, 24].

This may present as hoarseness, occasionally stridor and a sensation of a lump in the throat. A case report has been published where it was thought that a deficient carotid sheath predisposed to recurrent laryngeal nerve block following continuous interscalene block [25].

The cervicothoracic sympathetic trunk lies posterolaterally to the prevertebral fascia anterior to the longus colli muscle [26]. This is in close proximity to interscalene or supraclavicular brachial plexus block injection, hence involvement of the sympathetic trunk resulting in Horner’s syndrome.

Pneumothorax should be rare with ultrasound-guided interscalene block. Strategies have been suggested to reduce the risk of pneumothorax following ultrasound-guided supraclavicular blockade [27].

Contralateral spread is a rare complication of interscalene brachial plexus blockade [28, 29]. There may be more than one mechanism responsible for contralateral spread including spread in the tissue planes deep to the prevertebral fascia [30]. The risk of contralateral spread may be increased with increased exposure to the total dosage of local anesthetic (initial bolus and subsequent boluses or infusion). This complication should be taken into account when utilizing these techniques especially in the ambulatory setting.

Catheter location can be confirmed with a test dose and potentially ultrasound guidance.

The risks associated with performing a procedure close to the neuraxis are clear with interscalene blockade. Permanent neurological injury has been reported following injection of local anesthetic into the cervical spinal cord when an interscalene block was performed under general anesthesia [31].

Injection of local anesthetic into the vertebral artery or branches of the thyrocervical trunk can lead rapidly to local anesthetic toxicity.

Postoperative nerve injury regardless of etiology is of concern to patients and health-care providers. The reader should be aware that the methods used to capture, define, and report neurologic outcomes vary considerably. A single-center study reported the incidence of postoperative neurologic symptoms including those following interscalene block greater than 6 months duration was 0.9 per 1,000 blocks (95 % confidence interval, 0.5–1.7) [13]. Observational studies consistently report that postoperative neurologic dysfunction may be related to patient and surgical factors and that the incidence of serious permanent neuropathy directly related to peripheral regional anesthesia is rare. Neurologic complications include brachial plexopathy or injury to the dorsal scapular or long thoracic nerve. These nerves pass through or close to the middle scalene muscle and therefore ultrasound-guided interscalene block with a needle trajectory through this muscle, potentially introduces a new risk. Permanent phrenic nerve palsy is also a recognized although likely rare complication of interscalene brachial plexus block [32]. Distal mononeuropathies (involving the median and ulnar nerve) can occur following shoulder surgery and interscalene block, and these complications should be carefully evaluated taking into account all possible causes. Neurologic deficits in the C5–C6 distribution are more likely to be block related, compared to deficits in the ulnar distribution [9].

Supraclavicular brachial plexus block involves injecting local anesthetic around the divisions of the brachial plexus deep to the prevertebral fascia posterolateral to the subclavian artery.

Supraclavicular brachial plexus block was described in the early twentieth century by Kulenkampff and Persy [33] and was initially popular providing more effective anesthesia than other approaches to the brachial plexus. However, literature reviews and case series suggest an incidence of pneumothorax ranging from 0.5 to 6 % [34] and its popularity reduced [35]. Pneumothorax was the main deterrent to choosing this approach to the brachial plexus. More recently however, due to the popularity of ultrasound-guided regional anesthesia, with the potential to image the needle, brachial plexus, and pleura, the supraclavicular approach to the brachial plexus has increased in popularity as evidenced by case series [36], description of techniques [37], controlled clinical trials [38], and registries reports [11].

The anterior scalene muscle ends as a narrow tendon to insert on the scalene tubercle of the inner border of the first rib. Therefore, at this level, the anterior scalene muscle has a different morphology compared to at the interscalene level. In contrast, the middle scalene muscle inserts into a relatively larger area of the upper surface of the first rib (quadrangular area) and the muscle is relatively fleshy at the supraclavicular level. The prevertebral fascia over the brachial plexus at this level is well formed and distinct. The omohyoid muscle descends from the hyoid bone passes beneath the sternocleidomastoid over the carotid sheath to lie in the posterior triangle. The cylindrically shaped inferior belly of the omohyoid is often imaged and it passes almost horizontally above the level of the clavicle. The posterior triangle of the neck near the supraclavicular brachial plexus contains prominent vascular structures. These vessels include the dorsal scapular and suprascapular arteries (branches of the thyrocervical trunk or subclavian artery) often close to the planned needle trajectory or plexus and in some instances the vessels bisect the plexus [5].