Interscalene

The interscalene block (ISB) targets the brachial plexus at the level of the roots and trunks. This block traditionally could be done with a landmark approach and/or nerve stimulator but is now routinely accomplished with the use of ultrasound (US) guidance. ISBs are often performed for analgesia in surgeries involving the shoulder such as total shoulder arthroplasties and rotator cuff repairs, proximal humerus fractures, or surgeries of the distal clavicle. This approach reliably blocks the superior and middle trunks of the brachial plexus but will often result in sparing of the inferior trunk (C8–T1), commonly termed “ulnar sparing.”

To perform the ISB, the patient is placed in either a semi-sitting or a lateral position. If the patient is placed in the semi-sitting position, the head is turned towards the contralateral side. Identification of the target anatomy is done using a high-frequency US probe beginning at either the supraclavicular fossa or the cricoid cartilage. If starting at the supraclavicular fossa, first the subclavian artery is identified, with the brachial plexus sitting superior and lateral to the artery. Then the probe is slid cranially, tracking the brachial plexus. Another starting point is to place the probe on the lateral neck at the level of the cricoid cartilage (C6). The brachial plexus can be identified between the anterior and middle scalene muscles as a rounded, stacked structure resembling a “snowman” or “stop light.” Injections of 10–20 mL of local anesthetic are often used.

This block is performed in the neck and in proximity to the cervical sympathetic chain, recurrent laryngeal nerve, and phrenic nerve. Thus, it can result in Horner syndrome or hoarseness, and has a near 100% incidence of blocking the ipsilateral phrenic nerve. The resulting hemidiaphragm paralysis often goes unnoticed in healthy patients but can make it potentially unsuitable for patients with underlying respiratory disease. Other complications include vertebral artery injection, which may result in immediate seizures with injection of local anesthetic, and intrathecal injection resulting in total spinal anesthesia, pneumothorax, and permanent nerve injury.

Supraclavicular

The supraclavicular block (SB) is a block of the brachial plexus at the supraclavicular fossa that provides surgical anesthesia and analgesia to the upper extremity. The block requires deposition of local anesthetic around the brachial plexus as it courses through the neck in close association with the subclavian artery. This block is often referred to as the “spinal of the arm” due to its reliability and provision of excellent anesthesia for the entire length of the arm.

Prior to the advent of US-guided regional anesthesia, this block was rarely performed, owing to the proximity of the brachial plexus to the dome of the pleura. US reinvigorated clinicians to use this block routinely, as direct visualization of the plexus, pleura, and the first rib provided a wide margin of safety. The relative superficial depth of the brachial plexus at this location also provided for good imaging of the needle, further enhancing the safety of the SB.

The plexus can be readily seen in close proximity to the subclavian artery as the latter courses over the first rib and between the anterior and middle scalene muscles. The first rib is seen beneath the artery and plexus as a hyperechoic structure superficial to the mobile, “sliding,” and hyperechoic pleura. The upper, middle, and lower trunks of the brachial plexus coalesce into multiple round, hyperechoic structures within an investing fascia that sits lateral to the artery. The SB targets the brachial plexus at the level of the trunks and divisions. The practitioner needs to be aware of the path of the dorsal scapular artery, which often lies close to the plexus and can sometimes lie in the path of the needle trajectory.

This block is most commonly performed under US guidance with an in-plane approach. The block can be performed in a supine or semi-recumbent position, with the patient’s head turned to the contralateral side. A high-frequency, linear probe (10–12 MHz) is commonly employed and placed in the midpoint of the supraclavicular fossa and angled caudally to best visualize a cross-section of the subclavian artery. Color Doppler scanning can be used here to visualize any vessels that may lie in the anticipated needle trajectory, including the dorsal scapular artery, which can sometimes be seen arching over the brachial plexus. The needle is brought in plane to the deepest aspect of the brachial plexus and is associated with a palpable “pop” as the investing fascia of the plexus is pierced. A volume of approximately 20 mL of local anesthetic is required to achieve surgical anesthesia of the arm. Traditionally, local anesthetic is deposited close to the subclavian artery just above the first rib to ensure that there is spread of the drug in the deepest part of the plexus to avoid “ulnar sparing.” This is often referred to as “the corner pocket” and provides a characteristic appearance of the artery peeling off the first rib and spreading around the plexus. To ensure complete spread of the anesthetic, injections at multiple sites around the plexus may be necessary. Complications of the SB include intravascular injection, nerve injury, Horner syndrome, hemidiaphragm paralysis (phrenic nerve blockade), and pneumothorax.

Axillary

The axillary brachial plexus block is used for surgery of the elbow, forearm, and hand. This block derives its name from the approach used to perform it, as the nerves branched from the brachial plexus are accessed through the axilla. The axillary block is relatively easy to perform and mitigates some of the risks associated with comparable blocks such as the ISB (spinal cord or vertebral artery puncture) and SB (pneumothorax). The risk of phrenic nerve palsy is also considerably less than with brachial plexus blocks performed above the level of the clavicle. There are several techniques by which the block can be performed; these include transarterial approach, via nerve stimulation, and via US-guided techniques. US guidance is often favored as it allows for direct visualization of the nerves to be targeted, the needle tip, and the distribution of local anesthetic. To perform the block under US guidance, the arm is abducted 90°; then the insertion of the pectoralis major onto the humerus is palpated, and the transducer is placed distal to this point, perpendicular to the axis of the arm. The axillary artery, the conjoint tendon, and the terminal branches of the brachial plexus can be brought into view by sliding the transducer proximally. Three of the nerves to be blocked are located directly adjacent to the axillary artery – the median nerve superiorly, the ulnar nerve inferiorly, and the radial nerve posteriorly/laterally. Local anesthetic should be distributed between the nerves and the artery to ensure distribution within the neurovascular bundle. The musculocutaneous nerve is located either between the coracobrachialis and biceps muscles or within the coracobrachialis muscle itself. For this reason, vigilance on the part of the operator is required to avoid an incomplete block. It can be identified by its characteristic medial to lateral course in the axilla, as well as by its characteristic change in shape as it courses through the axilla (round adjacent to the artery, flat within the coracobrachialis muscle, and triangular after exiting the muscle).

Intercostobrachial

The intercostobrachial nerve (ICBN) block is commonly performed as a supplemental block in conjunction with blocks of the brachial plexus to obtain total upper arm analgesia. The ICBN supplies cutaneous sensation to the upper half of the medial/posterior arm and a portion of the anterior axilla. The nerve primarily originates from the second thoracic nerve but can have contributions from T1 and T3. As it is not part of the brachial plexus, it is not anesthetized when blocks of the brachial plexus are performed. Blocking of the ICBN may help to alleviate pain caused by tourniquet application to the upper arm, a common practice during surgeries of the arm, forearm, and hand. It is also useful in procedures involving the medial/posterior upper arm and/or for anterior arthroscopic port placement. The block is typically performed by subcutaneously injecting 2–5 mL of local anesthetic superiorly and inferiorly along the axillary crease with a fine-bore needle. Alternatively, the block can be performed under US guidance. One method of achieving this involves externally rotating and abducting the shoulder 90°, placing the probe over the posteromedial axilla, and visualizing the ICBN just posterior to the axillary artery and vein, and just deep to the superficial fascia. Placing the probe too anteriorly may result in inadvertent visualization of the medial cutaneous nerve of the arm, median nerve, or ulnar nerve.

Femoral Nerve Block and Adductor Canal Block

The femoral nerve is one of the largest nerves from the lumbar plexus. This nerve supplies a large portion of the lower extremity. It travels along the anteromedial thigh, traversing the femoral triangle and adductor canal, and terminates as the saphenous nerve – a pure sensory branch. The femoral nerve and its branches innervate the anterior thigh above the knee joint and the medial side of the lower leg and ankle. The extent of the saphenous distribution in the ankle is variable, potentially including the entire medial malleolus, and this must be considered in the regional anesthetic approaches to foot and ankle surgery. Indications for femoral nerve block (FNB) and adductor canal block (ACB) include partial or complete pain control for the anterior thigh and the medial side of the lower leg, such as partial or total knee arthroplasty (TKA), knee ligamentous procedures such as anterior cruciate ligament repair (ACLR), patella tendon repair, and tibial plateau fracture repair. Typical volumes used in FNB and ACB are around 20–40 mL, with lower concentrations (0.2% ropivacaine, 0.25% bupivacaine) for motor-sparing block or higher concentrations (0.5% ropivacaine, 0.5% bupivacaine) of local anesthetics for a more complete sensory and motor block. The FNB can be performed at the level of the inguinal crease level with a linear transducer. At this level, the neurovascular contents of the femoral triangle can be visualized. Under US guidance, the femoral nerve sits lateral to the femoral artery and vein, below the fascia lata and iliaca, and superficial to the iliopsoas muscle. The ACB targets the saphenous nerve and, dependent on the level at which it is performed, the nerve to the vastus medialis. Local anesthetic is deposited into the adductor canal between the sartorius and the adductor longus muscle in the middle third of the thigh under direct US guidance with a linear transducer. The ACB has increasingly replaced the FNB in procedures around or below the knee such as TKA, ACLR, and ankle surgeries, largely due to its ability to preserve quadriceps muscle strength and facilitate early ambulation, while maintaining similar level of analgesia as the FNB. The FNB has retained its indication for pain control in procedures or pathology more proximal to the adductor canal, such as procedures around the hip and proximal femur.

Obturator Nerve Block

The obturator nerve is a major branch from the lumbar plexus that provides motor and sensory innervation to the adductor muscles in the thigh, and sensory innervation to the skin over the medial surface of the thigh up to the posterior–medial knee. The sensory distribution of this nerve makes its blockade valuable in hip and knee analgesia. The obturator nerve block (ONB) has been used in acute pain management after several types of procedures around the knee, such as total knee replacement and ACLR, where it has been shown to improve postoperative analgesia. In addition, the ONB has been shown to be effective in acute pain management after hip fracture surgery in conjunction with the lateral femoral cutaneous nerve (LFCN) block, likely due to the blockade effect of the articular branch of the obturator nerve that innervates the anteromedial hip joint capsule. Several approaches of US-guided ONB have been proposed. Ergonomically, the patient is positioned supine, with a linear transducer employed. In the distal ONB, a volume of 10–15 mL of local anesthetic is injected into the interfascial space between the pectineus/adductor longus and the adductor brevis muscles to block the anterior branch, and between the adductor brevis and adductor magnus muscles to block the posterior branch. Alternatively, a single injection of local anesthetic in a volume of 5–10 mL can be injected into the interfascial plane between the pectineus and obturator externus muscles to block the obturator nerve at its confluence before it divides into two branches.

It is worth mentioning specific block complications germane to the ONB, owing to the particular location of these branches and the potential for unfamiliarity with the landmarks and sonoanatomy. These include penetration of the pelvic cavity and subsequent perforation of the bladder or rectum, as well as perforation of other surrounding structures, such as the obturator vessels, resulting in visceral organ injury or hematoma formation. Corona mortis, a retropubic anastomosis between the external iliac and obturator arteries, is present in 10% of individuals and, if perforated, can cause extensive hemorrhage that is difficult to control. The medial circumflex femoral vessels that travel along the obturator branches between the pectineus, obturator externus, adductor brevis, and adductor magnus must be carefully avoided, as they may lie in the needle path.