Chapter 25. Interscalene Brachial Plexus Block

The first brachial plexus blocks were performed by Halsted, in 1885, at the Roosevelt Hospital in New York City. Later Crile, in 1902, described an “open approach” to expose the plexus to the direct application of cocaine. At the time, however, the clinical applicability of this approach was limited because of the need for surgical exposure of the brachial plexus. Percutaneous access to the brachial plexus was described in the early 1900s. In 1925, Etienne1 reported the successful blockade of the brachial plexus by inserting a needle at the level of the cricothyroid membrane, halfway between the lateral border of the sternocleidomastoid and the anterior border of the trapezius muscle after a single injection through the area around the scalene muscles. This approach is most likely the first clinically useful interscalene block technique.

Different approaches were then tried until Winnie, in 1970,2 described the percutaneous technique of injecting local anesthetic into the groove between the anterior and middle scalene muscles at the level of the cricoid cartilage. This approach was the first consistently effective and technically suitable technique, and it allowed wider applicability of interscalene brachial plexus block. Winnie's approach was further modified, in line with numerous developments in regional anesthesia, by the placement of a perineural catheter, for example.3

Indications

Interscalene block is well suited for surgical procedures involving the shoulder, including the lateral two thirds of the clavicle, proximal humerus, and shoulder joint. Interscalene block can be used in the setting of arm or forearm surgery, but incomplete blockade of the inferior trunk often results in insufficient analgesia in the ulnar distribution. The patient's positioning and comfort, the surgeon's preferences, and the duration of surgery sometimes necessitate a combined general anesthesia. The indications for single-shot and interscalene catheter are summarized in Table 25–1.

Contraindications

Contraindications for interscalene brachial plexus block are rare. Absolute contraindications include patient's refusal, local infection, active bleeding in an anticoagulated patient, and proven allergy to local anesthetic. Relative contraindications include chronic obstructive airway disease, contralateral paresis of the phrenic or recurrent laryngeal nerves, and previous neurologic deficit of the involved arm. The risks and benefits of the chosen anesthetic technique should be discussed with the patient and the surgeon.

Anatomy

Understanding the relevant brachial plexus anatomy, ensuring precise needle location within the plexus diffusion space, and injection of appropriate volume and type of local anesthetic are fundamental for achieving high success rates with brachial plexus anesthesia. The plexus is formed by the ventral rami of the fifth to eighth cervical nerves and the greater part of the ventral ramus of the first thoracic nerve (Figure 25–1). In addition, small contributions may be made by the fourth cervical and the second thoracic nerves. The anatomy becomes complex because of the multiple connections to these ventral rami after they emerge from between the middle and the anterior scalene muscles until they end in the terminal nerves of the upper extremity. However, most of what happens to these roots on their way to becoming peripheral nerves is not clinically essential information to the anesthesiologist. Instead, broad concepts such as the spatial arrangement of the trunks (superior, middle, and inferior) and the muscular response elicited during electrostimulation can be helpful to clinicians (Table 25–2).

The brachial plexus supplies all the motor and most of the sensory functions of the shoulder except the cephalad cutaneous parts of the shoulder, which are innervated by the supraclavicular nerves originating from the lower part of the superficial cervical plexus (C3-4) (Figure 25–2). They supply sensation to the shoulder above the clavicle in addition to the first two intercostal spaces anteriorly. Furthermore, they supply sensation to the posterior cervical triangle and the upper thorax in this area as well as to the tip of the shoulder.6

Only three nerves of the brachial plexus have cutaneous representation in the shoulder. The most proximal of these is the upper lateral brachial cutaneous nerve, a branch of the axillary nerve that innervates the lateral side of the shoulder and the skin overlying the deltoid muscle. The upper medial side of the arm is innervated by both the medial brachial cutaneous and the intercostobrachial cutaneous nerves. In the anterior portion of the arm over the biceps muscle, the skin is innervated by the medial antebrachial cutaneous nerve.6

Apart from the cutaneous nerve supply to the shoulder, the innervation of the joint deserves special consideration. In general, a nerve crossing a joint gives branches that innervate it. Therefore, the nerves supplying the ligaments, capsule, and synovial membrane of the shoulder are fibers from the axillary, suprascapular, subscapular, and musculocutaneous nerves.7,8 The relative contributions of these nerves are variable, and the supply from the musculocutaneus nerve may be very small or completely absent. Anteriorly, the axillary nerve and suprascapular nerve provide most of the nerve supply to the capsule and glenohumeral joint (Figure 25–3). In some instances, the musculocutaneous nerve may innervate the anterosuperior portion of the joint. In addition, the anterior capsule may be supplied by either the subscapular nerves or the posterior cord of the brachial plexus after piercing the subscapularis muscle. Superiorly, primary contribution is from two branches of the suprascapular nerve, one branch supplying the acromioclavicular joint and proceeding anteriorly as far as the coracoid process and coracoacromial ligament and the other branch reaching the posterior aspect of the joint. Other nerves contributing to this region of the joint are the axillary nerve and musculocutaneous nerve. Posteriorly, the main nerves are the suprascapular nerve in the upper region and the axillary nerve in the lower region (Figure 25–4).

Inferiorly, the anterior portion is primarily supplied by the axillary nerve, and the posterior portion is supplied by a combination of the axillary nerve and lower ramifications of the suprascapular nerve.

Landmarks

The following surface anatomy landmarks are necessary for identifying the interscalene groove:

1. 1. Sternal head of the sternocleidomastoid muscle

2. 2. Clavicular head of the sternocleidomastoid muscle

3. 3. Upper border of the cricoid cartilage

4. 4. Clavicle

These landmarks should always be marked with a pen (Figure 25–5).

Equipment for Single-Shot Blockade

Standard regional anesthesia equipment for a single-shot blockade consists of the following items (Figure 25–6).

• Marking pen, ruler
• Sterile gloves
• Peripheral nerve stimulator, surface electrode
• Disinfection solution and sterile gauze packs
• 2- to 5-cm, short-bevel, 22-gauge insulated stimulating needle
• Syringes with local anesthetic

Equipment for Continuous Blockade

Standard regional anesthesia equipment for a continuous nerve block consists of the following items (Figure 25–7).

• Marking pen, ruler
• Peripheral nerve stimulator, surface electrode
• Disinfection solution, sterile gauze packs
• Sterile transparent drapes
• Syringes with local anesthetic for skin infiltration and block injection
• 25-mm, 25-gauge needle for skin infiltration at puncture point and for tunneling
• A set with stimulating needle for continuous nerve block and catheter
• Adhesive transparent tapes for securing the catheter
• Sterile gloves (cap, mask, and gown are optional)

Several approaches for interscalene block are known; with all modern techniques, the use of a nerve stimulator is recommended to localize the brachial plexus. The common techniques are those of Winnie, Pippa, modified lateral techniques (Meier and Borgeat), and the low interscalene approach.

Classic Technique (Winnie)

The classic approach of Winnie2 is performed at the level of the sixth cervical vertebra. Although Winnie originally used a paresthesia technique, most clinicians nowadays use a nerve stimulator technique.

1. 1. The patient is placed in a supine position with the head turned away from the side to be blocked.

2. 2. The patient is asked to elevate the head slightly to bring the clavicular head of the sternocleidomastoid muscle into prominence.

3. 3. The index and middle fingers of the nondominant hand are placed immediately behind the lateral edge of the sternocleidomastoid muscle. The patient is instructed to relax so that the palpating fingers can be moved medially behind this muscle and finally lie on the belly of the anterior scalene muscle.

4. 4. The palpating fingers are then rolled laterally across the belly of the anterior scalene muscle until they fall into the interscalene groove (formed by scalene anterior and posterior muscles).

5. 5. With both fingers in the interscalene groove, a 1½ in., 22-gauge, short-bevel needle is inserted between them at the level of C6 in a direction that is perpendicular to the skin in every plane.

6. 6. After a paresthesia (below the shoulder) is obtained, aspiration is carried out to rule out intravascular or intrathecal placement. While the patient is monitored closely for signs of local anaesthetic toxicity or inadvertent subarachnoid injection, 20–30 mL of local anesthetics are slowly injected.

Reported complications with this technique included total spinal anesthesia,9,10 epidural anesthesia,11 cervical cord injection with resultant paraplegia, as well as injections into the vertebral artery and the cervical spinal cord.12 Most of these complications are likely due to the perpendicular direction of the needle toward the cervical spine. Although an infrequent complication, pneumothorax can also occur with this technique. This technique is not well suited for the placement of an interscalene catheter because of the perpendicular approach to the trunks.

Posterior Approach (Pippa)

The posterior approach of Pippa13 is performed using the loss of resistance technique.

Landmarks

The approach of Pippa requires the following surface landmarks to be drawn on the skin (see Chapter 24).

• Point A—Midpoint between the cutaneous projections of the spinal process of the sixth and the seventh cervical vertebrae.
• Line B—Cutaneous projection of the superoexternal edge of the trapezius muscle–aponeurotic line.
• The point of needle insertion is where the horizontal line through point A intersects with line B.
• The point of needle insertion lies approximately 3 cm lateral to the interspinous line C6 and C7 and corresponds to the upper edge of the transverse process of the seventh cervical vertebra.

Technique

After local infiltration of the skin at the point of needle insertion, a 9-cm, 21-gauge needle is inserted and directed perpendicular to the skin through the trapezius, splenius cervicis, and levator scapulae muscles as far as the transverse process of the seventh cervical vertebra. The patient is then asked to turn the head to the contralateral side, and the needle (attached to a 5-mL syringe filled with air) is passed over the transverse process and advanced slowly through the posterior and middle scalene muscle into the interscalene space, where a “loss of resistance” can be felt.

The patient is then asked to move the head back to the original position. After negative aspiration for blood and cerebrospinal fluid, the local anesthetic solution is injected. Apart from transient side effects, such as reduction of pulmonary function and Horner syndrome,14,15 serious complications with Pippa's technique are not described. However, this technique represents a paravertebral approach to the brachial plexus and therefore can be associated with similar complications to those of Winnie's approach (eg, total spinal or epidural anesthesia; injections into the vertebral artery or the cervical spinal cord). This approach was recently modified by Boezaart.16 It is described in greater detail in Chapter 24.

Modified Lateral Technique (Meier)

To reduce the risk of complications and to allow the placement of an interscalene catheter for postoperative analgesia, Meier and coworkers17 modified Winnie's technique as follows.

• The same landmarks are identified as with Winnie's approach.
• The point of needle insertion is moved 2–3 cm cranial from the cricoid cartilage.
• In contrast to the technique of Winnie, the needle is not inserted perpendicularly, but at a 30-degree angle to the skin, and then directed toward the transition of the middle to the lateral third part of the clavicle.
• A nerve stimulator is used localize the brachial plexus in the interscalene groove.

This approach is also well designed for the placement of an interscalene catheter.

Modified Lateral Technique (Borgeat)

Similar to the technique described by Meier and coworkers,17 this approach to the interscalene brachial plexus is a modification of the classic technique of Winnie. The positioning of the patient's head, the identification of the landmarks, and the palpation of the interscalene groove are carried out in a similar way. The palpation of the interscalene groove is crucial because it provides important information about its shape, depth, and course at the lateral neck and helps the anesthesiologist to gain a three-dimensional image of the interscalene space.3

Technique

• After palpation of the interscalene groove, a line is drawn along the interscalene groove (Figure 25–8).
• Similar to the Winnie's technique, the point of needle insertion on this line lies 3–5 mm below the level of the upper part of the cricoid cartilage.
• A 5-cm, 22-gauge, short-bevel needle is used.
• The needle is directed caudally and slightly laterally or medially, depending on the plane of the interscalene space (see Figure 25–5).
• Motor response to nerve stimulation is sought in the posterior and dorsal part of the superior or middle trunk of the brachial plexus (preferentially, a triceps or sometimes deltoid response [C5, C6]).
• The position of the needle is considered appropriate if twitches are still present with a current output between 0.2 and 0.4 mA (100 μsec).

This approach is equally suitable for single-shot interscalene anesthesia as well as for continuous interscalene anesthesia and analgesia through an interscalene catheter.

Low Interscalene Brachial Plexus Block

The low interscalene technique of brachial plexus block18 differs in three important aspects from the classic approach and its modifications.

• Insertion of the needle is substantially below the cricoid cartilage and more lateral than with other approaches. This placement should reduce the risk of inadvertent insertion of the needle into the cervical cord as well as the risk of intraarterial injection into a vertebral artery.
• The brachial plexus is very superficial at this location; the skin to brachial plexus block distance is typically less than 1 cm and never deeper than 2 cm.
• The block can be considered anatomically and functionally a crossbreed between a classic interscalene block (the plexus is approached in the distal interscalene groove) and a supraclavicular block (the needle insertion is slightly above the clavicle).

In contrast to the other approaches, the low interscalene approach provides anesthesia for shoulder, elbow, and forearm surgeries alike.19

Landmarks

The landmarks for the low interscalene brachial plexus approach are as follows (Figure 25–9).

• Clavicle
• Posterior border of the clavicular head of the sternocleidomastoid muscle
• External jugular vein

Technique

The fingers of the palpating hand should be gently but firmly pressed between the anterior and middle scalene muscles to shorten the skin to brachial plexus distance (Figure 25–10). The palpating hand should not be moved during the entire block placement procedure to allow for precise redirections of the angle of the needle insertion when necessary. A needle connected to the nerve stimulator is inserted between the palpating fingers and advanced at an angle almost perpendicular to the skin plane and in a slight caudad direction (Figure 25–11). The nerve stimulator should be initially set to deliver l mA (2 Hz, 100 μsec). The needle is advanced slowly until stimulation of the brachial plexus is obtained. Once any motor response of the brachial plexus is elicited, 35–40 mL of local anesthetic of choice is injected slowly, with intermittent aspiration.

Continuous Interscalene Brachial Plexus Block

The continuous interscalene brachial plexus blockade is an advanced regional anesthesia technique, and adequate experience with the single-shot technique is necessary. Paradoxically, although the single-shot interscalene block is one of the easiest intermediate techniques to perform and master, placement of the catheter in the interscalene groove may be one of the more challenging continuous block techniques. This discrepancy is mostly due to the shallow position of the brachial plexus and difficulties in stabilizing the needle during catheter advancement. In addition, there is a difference in stimulating characteristics between the smaller-caliber single-shot and larger-caliber (often) Tuohy-style tip needles. The technique is otherwise similar to the single-shot injection with the exception that the needle is inserted at a lower angle to allow for threading the catheter. This technique provides excellent analgesia in patients after shoulder, arm, and elbow surgery.

Technique

The patient is positioned in the same position as in the single-shot technique. The subcutaneous tissues at the projected site of needle insertion are anesthetized with local anesthetic. The needle is attached to the nerve stimulator (1.0 mA, 2 Hz, 100 μsec) and to a syringe with local anesthetic. With this technique, it is imperative that the palpating hand firmly stabilizes the skin to facilitate needle insertion and insertion of the catheter. A 5-cm block needle is inserted at a slightly caudal angle and advanced until the brachial plexus twitch is elicited at 0.2 to 0.5 mA (Figure 25–12). While paying meticulous attention to the position of the needle, the catheter is inserted some 2–3 cm beyond the tip of the needle (Figure 25–13). The catheter is secured using a benzoin skin preparation, followed by application of a clear dressing. Some clinicians prefer to tunnel the catheter to prevent its accidental withdrawal (Figure 25–14). The infusion port should be clearly marked as: “continuous interscalene block,” and the catheter should be carefully checked for intravascular placement before administering larger volumes or infusion of local anesthetics. Before initiating the infusion of local anesthetic, the catheter is first checked for patency, and intravascular placement is ruled out by administering a small volume (2–3 mL of 1% lidocaine with epinephrine 1:300,000). The management of the continuous infusion of local anesthetic is discussed in the section about intraoperative management.

Sedation is almost always necessary to improve patient's comfort and satisfaction and the quality of the anesthesia achieved with an interscalene block. In addition, most surgeons prefer patients to be lightly asleep during surgery. Similarly, most patients also prefer not to be “aware” of activities in the operating room. Drugs most commonly used to accomplish perioperative sedation are propofol, midazolam, and an intravenous opioid. A face mask with oxygen (4–6 L/min) is routinely applied. Because most operating rooms are kept cold, all patients undergoing surgery under interscalene block should be kept warm by using forced air or warm blankets. The onset of shivering can turn a successful regional anesthetic into a significant intraoperative challenge.

Intraoperative use of pneumatic equipment close to the patient's ear can result in noise levels over 100 dB and significant amount of sedation is often needed to mask this noise.20 The use of earplugs, headphones with or without music, or blankets to cover the patient's ears and reduce the noise level can make a substantial difference in patient's comfort. Hyperhydration should be avoided because the patients typically do not have or require urinary bladder catheterization. It is a good idea to ask patients to empty their bladders before administering any drugs.

Choice of Local Anesthetics

For single-shot techniques, a variety of local anesthetic mixtures can be used (Table 25–4), depending on the desired duration and density of blockade. This author prefers to use ropivacaine rather than bupivacaine and levobupivacaine because of the greater safety profile of ropivacaine.

The typical volume of local anesthetic used for interscalene blocks is 30–45 mL. The expected duration of the block varies between 3 and 5 hours with mepivacaine 1.5% or 2% and lidocaine 1.5%21,22 and 8–12 hours with bupivacaine 0.5% and ropivacaine 0.5 or 0.75%.23,24 The duration of action is also proportional to the volume and dose administered. Clonidine,25 but not opioids,26,27 can prolong the duration of both anesthesia and analgesia with intermediate-acting local anesthetics.25 The addition of epinephrine also prolongs the duration of action of most local anesthetics.28 Results of studies that compared the outcome of interscalene block with that of general anesthesia in patients undergoing shoulder arthroscopy suggest that interscalene block provides a number of important advantages over general anesthesia in the outpatient setting.21,29 The interscalene block provided excellent anesthesia and muscular relaxation, fewer postoperative side effects and hospital admissions, and a shorter hospital stay. It is important to note that complete recovery of the motor blockade is no longer a requirement before discharge home,30 making the long-acting anesthetics more appropriate in this setting, even for day-case surgery.

Continuous infusion of local anesthetics through an interscalene catheter compared with traditional patient-controlled analgesia (PCA) with opioids provides significantly better control of pain, with a statistically significant lower incidence of side effects and greater patient satisfaction.31,32 Catheters are typically left in place for 2–3 days. The use of a continuous infusion of 0.125% bupivacaine at a rate of 0.125 mL/kg per hour was shown to provide efficient pain relief, but at the cost of administrating a large volume of local anesthetics.32 A better infusion protocol for perineural blocks would be to incorporate a PCA dose, which allows patients to affect the dynamic nature of the pain.

Either bupivacaine 0.15% or ropivacaine 0.2% as a primary agent at a rate of 5 mL/h plus a supplemental bolus of 4 mL/20 min was associated with better pain control; lower incidence of nausea, vomiting, and pruritus; and better patient satisfaction, compared with the classic PCA with opioids.31,33

Ropivacaine 0.2%, compared with interscalene PCA with bupivacaine 0.15%, was associated with better preservation of hand strength 24 and 48 hours after the beginning of the infusion, as well as 6 hours after the infusion was stopped.34 Therefore, ropivacaine, compared with bupivacaine, may have better sensorimotor dissociation.35,36

Complications associated with the different techniques of interscalene block are summarized in (Table 25–5). The most common side effects encountered after interscalene block are hoarseness (10–20%) due to the blockade of the recurrent laryngeal nerve, which occurs more frequently on the right side. Claude-Bernard-Horner syndrome is characterized by ptosis, myosis, and enopthalmia due to the diffusion of the local anesthetic solution on the sympathetic cervical ganglion chain (including the stellatum ganglion) (Figure 25–15). The reason for this syndrome is the spread of the local anesthetic around the anterior scalene muscle behind the carotid artery and internal jugular vein toward the longus colli muscle (Figure 25–16). This results in blockade of the cervical ganglion (Horner syndrome) and phrenic nerve, which are located in this area. In addition, superior laryngeal nerve can be affected. It occurs in 40–60% of patients and resolves with resolution of the block; patient reassurance is all that is needed for management. Ipsilateral hemidiaphragmatic paresis is a common finding and may be present in nearly 100% of patients37 (Figure 25–17). This finding, however, rarely presents a problem clinically, and many patients are not even aware of it. The occurrence of the paradoxical Bezold-Jarisch reflex, that is, sudden bradycardia and hypotension (15–30%), is favored by the sitting position and can be often prevented by avoiding hypovolemia. It is easily treated by atropine and ephedrine administration.

Complications

Early complications (soon after block administration), such as epidural or spinal injection and intravertebral injection, are primarily related to the approach chosen (Table 25–5). Late complications include neuropathy, mechanical plexus injury, and infection.

Nerve injuries are a well-recognized complication of anesthesia.38,39 It is generally believed that regional techniques are more prone to induce nerve damage because the aim of these techniques is to deposit the local anesthetic in close vicinity to the nerve. However, Kroll and coworkers39 reported that 60% of the claims for nerve damage occurred after general anesthesia, with the reserve that more procedures were performed under general than under regional anesthesia. Postoperative brachial plexus plexopathy is well documented to occur regardless of the type of anesthesia administered. The American Society of Anesthesiologists, using the Closed Claims Database, performed a systematic analysis of nerve injury associated with anesthesia.39 The results of this large study revealed that nerve damage represented 16% of the 4183 claims analyzed. The distribution of the nerve injury (670 cases) showed that the most common nerve injury involved the ulnar nerve (28%), immediately followed by the brachial plexus (20%). Among these, 78% and 22% occurred after general and regional anesthesia, respectively. Except for cases associated with spinal cord damage, no specific mechanism to explain these events was evident. However, in the cases of brachial plexus damage, factors related to patient position, such as the use of shoulder braces and the head position, malposition of the arms, and sustained neck extension were observed frequently. Little data are available on the rate of complication related to the use of the continuous interscalene catheters.40,41Table 25–6 lists reported complications of interscalene blocks and suggestions on how to avoid them.

Interscalene nerve block is one of the most commonly used and most clinically applicable nerve block techniques. Modern techniques and equipment, when combined with appropriate training, result in a predictable success rate, excellent anesthesia, and superb postoperative analgesia. Recent studies affirmed the clinical impression that interscalene blocks offer several independent advantages over general anesthesia in outpatients undergoing shoulder surgery. Continuous interscalene block is a relatively new modality that can be used to extend the advantages of single-injection interscalene blocks well into the postoperative period.