Roots, trunks, divisions, cords, and branches of the brachial plexus (Reproduced from Elsevier, Miller’s Anesthesia , Ronald D. Miller MD, MS , 2015, Ch 57, pp 1724–1724, Figure 57-3)
An interscalene block is recommended for shoulder and proximal humerus surgical procedure therefore ideal for reduction of dislocated shoulder. When performed the roots of the brachial plexus (C5- C7) are most commonly blocked with this technique. Due to location, blockage of the ulnar nerve, which originates from C8-T1, usually does not occur; and for complete surgical anesthesia of the shoulder, the C3-C4 cutaneous branches may need to be block with local infiltration or use of superficial cervical block. Interscalene blocks are appropriate in nearly all patients, even the obese due to ease of identifiable necessary landmarks [2–4]. However, Interscalene blocks should be avoided in patients with significant impaired pulmonary function due to blockage of the phrenic nerve and in patients with contralateral vocal cord paralysis . Contraindication includes local infection, severe coagulopathy, local anesthetic allergy, and patient refusal.
Surface anatomy of importance includes the larynx, sternocleidomastoid muscle, and external jugular vein. This block can be performed with the arm in any position. The patient should be in the supine position, with the head turned away from the side to be blocked. The block is often performed at the level of the C6 vertebral body, which is at the level of the cricoid cartilage. The plexus courses between the anterior and middle scalene muscles, superior and posterior to the second and third parts of the subclavian artery. The interscalene groove can be palpated by rolling the fingers posterolaterally over the anterior scalene muscle into the groove. A line is extended laterally from the cricoid cartilage to intersect the interscalene groove, indicating the level of the transverse process of C6 . Although the external jugular vein often overlies this point of intersection, it is not a constant or reliable landmark .
This block is well suited with ultrasound guidance as it is easy to obtain a supraclavicular view of the subclavian artery and brachial plexus; then trace the plexus up the neck with the ultrasound probe until the plexus are visualized as hypoechoic structures between the anterior and medial scalene muscles [4, 5]. A 22–25-gauge with 4-cm needle should be used. The needle is inserted perpendicular to the skin with a 45° caudad and slightly posterior angle [2, 5]. The needle is then advanced in an out-of-plane or an in-plane approach until a paresthesia or nerve stimulator response is elicited. After desired response is obtained and there is negative aspiration, local anesthetic solution is injected incrementally depending on the desired extent of blockade. This is one of the brachial plexus block in which large volume of local anesthetic allows effective anesthesia therefore large volumes up to 40 ml are typically used [1–4, 6].
Side Effects and Complications
Blockage of the ipsilateral phrenic nerve block is almost guaranteed with the interscalene block, which result in diaphragmatic paresis in majority of patients, even with dilute solutions of local anesthetics, and is associated with significant reduction in pulmonary function [2, 6]. Hemidiaphragmatic paresis may result in dyspnea, hypercapnia, and hypoxemia. Techniques to decrease blockade of the phrenic nerve include using very small volumes of local anesthetic and localizing the brachial plexus at a lower level in the neck. Horner’s syndrome may also result from blockage of sympathetic fibers to the cervicothoracic ganglion. The risk of pneumothorax is small when the needle is correctly placed at the C5 or C6 level because of the distance from the dome of the pleura. The proximity of significant neurovascular structures can increase the risk of serious neurologic complications when an interscalene block is performed in heavily sedated or anesthetized patients . Therefore, an interscalene block should be placed with the patient awake or under light sedation.
The supraclavicular block is recommended for procedures of the upper arm, elbow, forearm, wrist, and hand. This technique blocks the divisions of the brachial plexus, at this level the distal trunk-proximal division of the brachial plexus is compact therefore the supraclavicular block result in faster onset and effective blockage of almost the entire upper extremity below the shoulder compared to other upper extremity blocks . Studies have shown small volume of local anesthetic produces rapid onset of reliable blockade of the brachial plexus [4, 5, 7].
The neurovascular bundle of the brachial plexus lies midpoint inferior to the clavicle and the nerve bundles are located vertically over the first rib posterior to the subclavian artery, which can be palpated in some patients. The first rib which is short, broad, and flat, with an anteroposterior orientation at the site of the plexus typically prevents the needle’s reaching the pleural. Contraindication includes local infection, severe coagulopathy, and patient refusal. This block is cautioned in patients who are uncooperative or cannot tolerate any degree of respiratory compromise.
The patient is positioned supine with the head turned away from the side to be blocked with then arm adducted and the hand extended along the side. The midpoint of the clavicle is typically identified and the posterior border of the sternocleidomastoid palpated over the anterior scalene muscle into the interscalene groove, identification of the subclavian artery at this point confirms the landmark. With the use of the ultrasound one can visualize the brachial plexus structures, as well as the subclavian artery and pleura, just below the first rib . A 22-gauge, 4-cm needle is directed in a caudad, slightly medial to posterior direction until a paresthesia or motor response is elicited or the first rib is encountered. If the first rib is encountered without elicitation of a paresthesia, the needle can be systematically moved anteriorly or posteriorly along the rib with continuous visualization of the needle tip with the ultrasound until the other landmarks are located such as the subclavian artery/vein and pleura. After localization of the brachial plexus, aspiration for blood should be performed before incremental injections of local anesthetic.
Side Effects and Complications
The supraclavicular block is more difficult to perform on obese patients, however there is no increased risk of complications documented . The prevalence of pneumothorax after supraclavicular block is 0.5–6 % and diminishes with increased experience and use of ultrasound . If pneumothorax occurs the onset of symptoms is usually delayed and it can take up to 24 h therefore a routine chest radiography post procedure is not recommended . Other complications include phrenic nerve block, at a lesser degree than the interscalene block, Horner’s syndrome, and neuropathy, which usually is self-limited.
The infraclavicular block is recommend for procedures at or distal to the elbow, arm, and hand. It provides blockage of the brachial plexus at the level of the cords. An ultrasound and nerve stimulator is required with this block because there are no palpable vascular landmarks to aid in directing the needle. This technique is distal from the neuraxial structures and the lungs, thus minimizing the complication of an interscalene or supraclavicular block.
The Patient is typically positioned supine but no special arm positioning is required. The ultrasound is placed below the midpoint of the inferior border of the clavicle near the palpable coracoid process and used to visualize the neurovascular bundle. The needle is inserted and advanced laterally until, the brachial plexus identified and confirmed by the nerve stimulator. An incremental local anesthetic is injected around the axillary artery.
Side Effects and Complications
Due to the proximity of the axillary artery there is risk of vascular puncture and systemic local anesthetic toxicity. It is recommended to avoid this approach on patient with catheters or pacemakers at this region .
Among the brachial plexus blocks, the axillary approach is by far the most popular due to its ease, reliability, and safety [3, 4]. Blockade occurs at the level of the terminal nerves therefore it is suitable for procedure of the forearm and hand. The musculocutaneous nerve however is usually spared, at this level as it has already left the sheath and lies with the coracobrachialis muscle. This block is suited for outpatients and is easily adapted to the pediatric population [4, 7]. Arm position is very important therefore axillary blockade is unsuitable for patients who are unable to abduct the arm to perform the block.
The patient should be placed in supine position with the arm to be blocked placed at a right angle to the body, elbow flexed to 90°. The dorsum of the hand rests on a bed or pillow. The axillary artery can then be palpated and traced from the lower axilla to as proximal as possible. The artery is then fixed against the patient’s humerus and the ultrasound is placed to visualize neurovascular bundle. Although anatomic variations exist the median nerve is typically found superior to the artery, the ulnar nerve is inferior, and the radial nerve is posterior to lateral. A short 22-gauge needle is then inserted and advanced until the axillary sheath is entered and desire (including muscular cutones) nerve stimulation is obtained. Local anesthetic is injected after negative aspiration. The ultrasound aids visualization of local anesthetic spread around the nerves. Proximal needle placement and maintenance of distal pressure facilitate proximal spread of the solution.
Terminal Nerve Blocks
Peripheral nerve blocks are useful for procedures at the wrist and elbow requiring limited anesthesia or has contraindications to brachial plexus block such as infection, bilateral procedure, coagulopathy, or difficult anatomy [2, 8]. Peripheral blocks performed at the level of the elbow and wrist are typically performed as “field” blocks without requiring the use of nerve stimulator or ultrasound. Benefits include ease of blocks and reduce complications.
Median Nerve Block
The median nerve originates from the lateral and medial cords of the brachial plexus. It travels medial to the brachial artery. In the antecubital space, it is medial to the insertion of the biceps tendon. It gives off multiple motor branches before it enters the carpal tunnel. Then it is located between the flexor carpi radialis and palmaris longus tendon in the carpal tunnel.
Blocking the median nerve provides anesthesia to the palmar surface of the first, second, third, and lateral half of the fourth digit, motor blockade causing Loss of pronation of forearm, weakness in flexion of the hand at the wrist, loss of flexion of radial half of digits and thumb, and loss of abduction and opposition of thumb. The median nerve block requires the patient’s arm supine, the medial and lateral epicondyles of the humerus identified. The major landmark for this technique is the brachial artery, which is found medial to the biceps tendon at the intercondylar line.
To block the median nerve at the elbow, one identifies the brachial artery in the antecubital crease just medial to the biceps insertion and inserts a short 22-gauge needle just medial to the artery, and directed toward the medial epicondyle until desired wrist flexion and/or thumb opposition is obtained. A small amount of local anesthetic is then injected.
The median nerve is blocked at the wrist by identifying the palmaris longus tendon which can be discentered when the patient is instructed to flex at the way. A short 22-gauge needle is inserted just medial to the palmaris longus tendon at the carpal tunnel and small amount of local is injected.
Radial Nerve Block
The radial nerve originates from the terminal branch of the posterior cord of the brachial plexus and travels posterior to the humerus innervating the triceps and entering the spiral groove of the humerus. It then moves laterally at the elbow and travel thru the posterior lateral of the forearm.
Blockage of the radial nerve provides anesthesia to the lateral aspect of the dorsum of the hand and the proximal portion of the first, second, third and lateral half of the fourth digit. The Radial nerve can be block at the elbow or the wrist.
The radial nerve is blocked at the elbow by locating the biceps tendon and tracing it until it contacts the epicondyle. A small 22 gauge needle is inserted lateral to the biceps tendon near the epicondyle, a small local anesthetic is inject around the radial nerve as it passes over the anterior aspect of the lateral epicondyle.
The radial nerve is blocked at the wrist by identifying the palmaris longus and flexor carpi radialis tendon. A small needle is inserted over this tendon at the base of the first metacarpal; a small local anesthetic is injected proximally along the tendon and a right angle across the anatomic snuffbox. This injection tends to be very superficial.
Ulnar Nerve Block
The ulnar nerve originated from the medial cords of the brachial plexus and travel alongside the axillary and brachial arteries. It is easily located in the ulnar groove, which is bony space between the medial epicondyle of the humerus and olecranon process. In the forearm the nerve travel between the flexor digitorum profundus and the flexor carpi ulnaris.
Blockade of the ulnar nerve provides anesthesia of the ulnar side of the hand, the fifth digit, the medial part of fourth digit, and all the small muscles of the hand, except the thenar eminence and the first and second lumbrical muscles.
At the elbow, the ulnar nerve is blocked by inserting a small needle proximal to the arcuate ligament and posterior to the medial epicondyle until desire the nerve stimulation is obtained. Due to the superficial location of this nerve at this site there is a high incidence of nerve injury.
At the wrist, the ulnar nerve is located beneath the flexor carpi ulnaris tendon between the ulnar artery and the pisiform bone. The nerve is blocked by placing the needle alongside the tendon until desire nerve stimulation is obtained. A small anesthetic is injected alongside the area.
Musculocutaneous Nerve Block
The musculocutaneous nerve originates as the terminal branch of the lateral cord. It innervates the biceps, brachialis muscles, and terminates as the lateral cutaneous nerve of the forearm providing sensory to the radial side of the forearm up to the radiocarpal joint.
The musculocutaneous nerve block is usually performed as a supplement block to the axillary block of the brachial plexus. The nerve is usually located superior and proximal to the brachial artery thru the coracobrachialis muscle. An ultrasound is helpful to visualize the nerve between the muscle tissues. A small amount of local anesthetic is then injected along the nerve.
Side Effects and Complications
In general, terminal peripheral nerve blocks have a less frequent risk of complications. However there is a higher risk of nerve injury due to the nerves being superficially placed between ligamentous and bony structures . Intravascular injection can occur therefore injection after aspiration is recommended.
Intravenous Regional Blocks
Intravenous regional blocks also known as Bier block were first described in 1908 by a German surgeon, August Bier [1–3, 6]. The technique involves the patient resting supine an intravenous cannula placed. Proximal and distal tourniquets are then applied on the desired limb. The goal of the tourniquet is to contain the anesthetic injected locally therefore cuffs should have secure closures and reliable pressure gauges. The Bier block has multiple advantages, including ease of administration, and rapid onset and recovery; therefore it is excellent for short procedures.
Prior to the intravenous administration of local anesthetic the desired limb is first exsanguinated by either tightly wrapping the extremity with an Esmark elastic bandage from distal to proximal direction or elevating it for 3–4 min to allow gravity to exsanguinate it . The proximal cuff is then inflated greater than the systolic pressure until the absence of a distal pulse. The local anesthetic is then injected slowly; the total dose is based on the patient’s weight . The onset of anesthesia is usually within 5 min. When the patient complains of tourniquet pain, the distal tourniquet, which overlies anesthetized skin, is inflated, and the proximal tourniquet is released. The tourniquet can be safely release slowly after 25 minutes and the patient monitored closely for local anesthetic toxicity. For very short duration procedure the tourniquet must be left inflated for at least 15–20 min to avoid rapid intravenous systemic bolus of local anesthetic resulting into toxicity.
Side Effects and Complications
Most common problems associated with bier blocks include tourniquet discomfort, painful exsanguination, and rapid recovery leading to postoperative pain [2, 6]. Early deflation of the tourniquet or excessive doses of local anesthetics can result in systemic anesthetic toxicity. Rare complications including development of compartment syndrome and limb loss have also been noted [2, 8].
Lower Extremity Blocks
The most common indication for regional anesthesia outside of the OR is hip fracture. Pain from hip fracture, both intracapsular and extracapsular, can be treated with a lower extremity nerve block . These blocks include femoral nerve block, fascia iliaca block, and lumbar plexus block. The femoral nerve block, sometimes called a 3-in-1 block, is an excellent block to treat pain from hip fracture and other injuries to the leg [11, 12]. A fascia iliaca block can also be used to treat hip and lower extremity pain, however, the efficacy of the femoral nerve block is greater than the fascia iliaca block . A lumbar plexus block can also provide pain relief for hip fracture, however, the block is technically challenging, has a higher complication rate than the femoral block, and should only be performed by those with advanced training in nerve blocks [1, 14]. In addition, the femoral block is as effective as the lumbar plexus block in controlling pain after surgical repair of hip fractures .
The femoral nerve innervates the leg- including the anterior and medial thigh distally to the knee and the medial aspect of the lower leg and foot. The femoral nerve also provides branches to the hip.
Hip fracture, injury to the anterior or medial thigh, femur, or knee
The femoral nerve block is done adjacent to the femoral artery, in the inguinal crease. The block is usually done in the supine position, although some practitioners prefer Trendelenburg positioning of the table if the goal is analgesia to the hip . The area should be prepped and draped in a sterile fashion. In the obese patient, tape can be used to secure the pannus out of the procedure field. The pulsation of the femoral artery can be used as a landmark in correct placement of the ultrasound transducer, although this can be difficult in the obese patient, and it is not necessary for the procedure. The ultrasound transducer should be placed in the inguinal crease in a transverse plane and adjusted until the femoral artery is identified. The femoral nerve can then be located lateral to the femoral artery, deep to the fascia illaca, superficial to the iliopsoas muscle. The femoral nerve is hyperechoic and can be oval or triangular in shape.