What Are the Options for Pain Control Postoperatively?

Surgical operations of the shoulder involve a significant amount of postoperative pain. A few options to treat the pain postoperatively include intravenous pain medications, with opiates being the foundation of a standard pain control regimen. In addition, NSAIDs and acetaminophen are frequently employed in a multimodal regimen. Administration of the opioid is most commonly done with patient-controlled analgesia (PCA). Opioid PCAs have been used extensively in children as young as eight years old with great efficacy and pain control. Children less than eight years of age may have difficulty using PCA. An alternative option would be an interscalene brachial plexus nerve block or catheter placement to manage postoperative pain control.

The brachial plexus innervates nearly the entire upper extremity. The plexus arises from the ventral rami of spinal nerves C5-T1 with occasional contribution from C4 and T2. The plexus transitions as it divides into the arm from five roots to three trunks to six divisions to three cords and five major branches. Each of the upper extremity nerve blocks targets a particular portion of the brachial plexus in its division (Figure 51.1).

Figure 51.1 From left to right, the axillary, infraclavicular, supraclavicular, and interscalene blocks are highlighted with the division of the brachial plexus targeted.

Reproduced with permission from Arbona FL, Khabiri B, Norton JA (eds.) 2011. Ultrasound-Guided Regional Anesthesia: A Practical Approach to Peripheral Nerve Blocks and Perineural Catheters. Cambridge, UK: Cambridge University Press

What Are the Indications for an Interscalene Brachial Plexus Block?

An interscalene brachial plexus block is ideal for any operation involving the shoulder and upper extremity. It involves the blockade of the brachial plexus at the level of the superior (C5/C6), middle (C7), and inferior trunks (C8) in the interscalene groove between the anterior and middle scalene muscles. Since the suprascapular nerve arises off the brachial plexus just after the interscalene groove but prior to the supraclavicular position, a supraclavicular nerve block cannot reliably provide analgesia to operations involving the shoulder. There is a degree of ulnar sparing that occurs making the use of an interscalene block for procedures below the elbow less optimal than a supraclavicular, infraclavicular or axillary brachial plexus block. The block can be done as a single shot or with placement of a catheter to allow for continuous nerve blockade post-operatively to provide analgesia as well as facilitate initial rehabilitation and physical therapy.

What Are the Contraindications to Performing an Interscalene Block?

The standard contraindications for any regional block apply: patient refusal is an absolute contraindication. Relative contraindications include infection at planned injection site, preexisting neurologic deficits, local anesthetic allergy, coagulopathy, as well as impaired respiratory reserve such as contralateral phrenic nerve palsy, diaphragmatic impairment, or chronic obstructive pulmonary disease (COPD).

What Are the Complications and Side Effects Associated with an Interscalene Block?

The complications of an interscalene block include pneumothorax, epidural or subarachnoid injection, permanent neurological injury, and vagal and/or recurrent laryngeal nerve blockade. With the increased utilization and ability to visualize target structures, the rate of complications has fallen precipitously. Common side effects of an interscalene block include a Horner’s syndrome from blockade of the cervical sympathetic nerves as well as phrenic nerve blockade. Both nerves are in close proximity to the interscalene brachial plexus and have higher incidences with increased volumes of injection for nerve blockade.

What Is the Incidence of Phrenic Nerve Blockade When Performing an Interscalene Block? How Can That Be Avoided?

The occurrence of phrenic nerve blockade resulting in ipsilateral diaphragmatic paralysis was traditionally stated to be 100% owing to the close proximity of the phrenic nerve to the interscalene brachial plexus in its interscalene groove. Anatomically, the phrenic nerve lies in an anterolateral position on the anterior scalene muscle surface. However, there is considerable variability in the anatomic position. With use of ultrasound, decreased volume of local anesthetic, and differential needle approaches to avoid the phrenic nerve, there has been a small decrease (<20%) in the incidence of phrenic nerve blockade, but reliably avoiding the phrenic nerve has proven elusive.

How Is an Interscalene Block Performed?

With the traditional nerve stimulation technique, the patient was positioned with the head turned toward the contralateral side to be blocked. The interscalene groove was identified at the level of C6 (cricoid cartilage) posterolateral to the clavicular head of the sternocleidomastoid between the anterior and middle scalene muscles. The needle would be advanced until twitches were elicited in the brachial plexus distribution (deltoid, biceps, triceps, or hand).

The predominant method of performing an interscalene block currently is with ultrasound guidance (Figures 51.2–51.4). For smaller children, a linear ultrasound transducer with the smallest available footprint allows for optimal visualization of target structures with adequate surface area for needle approach. The ultrasound image below is the desired image to acquire.

Figure 51.2 Patient and probe positioning for in-plane interscalene nerve block.

Reproduced with permission from Arbona FL, Khabiri B, Norton JA (eds.) 2011. Ultrasound-Guided Regional Anesthesia: A Practical Approach to Peripheral Nerve Blocks and Perineural Catheters. Cambridge, UK: Cambridge University Press

Figure 51.3 Interscalene anatomy.

Reproduced with permission from Arthurs G, Nicholls B (eds.) 2016. Ultrasound in Anesthesia, Critical Care, and Pain Management. Cambridge, UK: Cambridge University Press

Figure 51.4 Ultrasound anatomy of interscalene nerve block. CA, Carotid Artery; IJ; Internal Jugular Vein; SCM, Sternocleidomastoid; AS, Anterior Scalene; MS, Middle Scalene; BP, Brachial Plexus

Local anesthetic would be deposited in aliquoted fashion with frequent aspiration to avoid intravascular or intrathecal injection. Typical dosing for a single-shot block would be 0.2–0.4 cc/kg of ropivacaine 0.2%–0.5% or bupivacaine 0.25%–0.5%. If a catheter is placed for postoperative pain control, a typical infusion rate is 0.1–0.2 mL/kg/h of ropivacaine 0.1–0.2% or bupivacaine 0.1–0.25%.