BLOCK AT A GLANCE
Blockade of the brachial plexus at the level of the interscalene space.
Indications: Anesthesia and analgesia for shoulder, upper arm, and clavicle surgery
Goal: Local anesthetic (LA) spread around the superior and middle trunks of the brachial plexus, between the anterior and middle scalene muscles
Local anesthetic: 5 to 15 mL
The interscalene brachial plexus block is a common regional anesthesia technique for anesthesia and analgesia of the shoulder and upper arm surgery, as it provides complete blockade of the nerves involved in the innervation of the shoulder (Figure 13-1). Ultrasound (US) guidance has improved the block’s success and popularity and reduced the volume of LA required. Ipsilateral phrenic nerve block with consequent hemi-diaphragmatic palsy remains the most common adverse effect of the interscalene block despite several modifications of the technique to decrease its occurrence. Using lower volumes (<10 mL), diluted LAs, more distal injection sites, selective superior trunk block, or a combination of these interventions does decrease the incidence, but does not consistently avoid block of the phrenic nerve. Therefore, this block should be used with caution in patients with respiratory insufficiency; more distal interventional techniques are recommended instead. (See Chapter 18.)
Innervation of the shoulder joint; all neural elements come from the brachial plexus at the interscalene level.
Procedural injuries of the interscalene brachial plexus have been reported, including nerve injury of the median, radial, phrenic, dorsal scapular, and long thoracic nerves. The recurrent laryngeal nerve may also be blocked with interscalene block, resulting in airway obstruction in patients with existing vocal cord palsy. Epidural or spinal injection, Horner syndrome, diaphragmatic paralysis, and myotoxicity have all been reported.
The brachial plexus is a nerve network comprised of the anterior rami from the spinal nerves from C5 to T1 (Figure 13-2). The spinal nerves continue to form roots, trunks, divisions, cords, and branches. At the posterior triangle of the neck, the plexus is seen as three trunks (superior, middle, and inferior) posterior to the carotid artery and internal jugular vein between the anterior and middle scalene muscles. The phrenic nerve courses anterior to the brachial plexus over the surface of the anterior scalene muscle (Figure 13-3). The dorsal scapular nerve runs down and posterior through the middle scalene muscle, often close to the long thoracic nerve. Anatomical variations in brachial plexus anatomy are common. As an example, the C5 root often (35%) takes a course over or through the anterior scalene muscle rather than the interscalene space. The branches of the thyrocervical trunk (suprascapular artery and transverse cervical artery) cross the brachial plexus at variable levels as they travel posteriorly.
Organization of the brachial plexus from ...