Indications, anatomy, and complications

The axillary block provides analgesia to the elbow, forearm, and hand. The terminal branches of the brachial plexus, the median, radial, and ulnar nerves, lie superficially in the axilla where they can be blocked as they surround the axillary artery. Although anatomic variations exist, the ulnar nerve is most commonly located anterior and inferior to the artery, and the radial nerve lies posteriorly. The median nerve is usually located superior and anterior to the axillary artery ( Fig. 1 ). An important consideration to successfully perform this block is the location of the musculocutaneous nerve, as it lies outside the axillary neurovascular sheath and therefore must be blocked separately from the other nerves. This nerve provides sensation to the posterior aspect of the forearm and is located between the biceps brachii and coracobrachialis muscles.

Axillary approach to the brachial plexus block. AA, axillary artery; MN, median nerve; RN, radial nerve; UN, ulnar nerve.

Ultrasound-guided axillary blocks in the pediatric literature are not well described, but the techniques used in adults can be applied. ^, With the ultrasound probe placed transverse to the humerus, an out-of-plane technique may be used. Circumferential spread of local anesthetic can be achieved with multiple injections while repositioning the needle, which must be done carefully, given the axillary sheath’s superficial depth. ^,

Complications of an axillary block include infection, intravascular injection, hematoma, and nerve injury. With ultrasound guidance, the risk of accidental intravascular injection into the axillary artery is likely reduced.

Indications, anatomy, and complications

The interscalene block provides analgesia to the shoulder and proximal humerus. This brachial plexus block is performed at the interscalene groove, where the trunks and roots lie posterior to the sternocleidomastoid muscle. The nerve roots, C5–C7, lie between the anterior and middle scalene muscles ( Fig. 2 ). The C8 and T1 dermatomes are often spared, so this block may not adequately cover more distal procedures of the arm.

Interscalene block. Arrows indicate the interscalene groove. AS, anterior scalene muscle; MS, middle scalene muscle.

This block can be performed under ultrasound guidance by placing the probe in the transverse oblique plane at the lateral edge of the sternocleidomastoid muscle, at the level of the cricoid cartilage. The interscalene groove, which is located deep to the sternocleidomastoid muscle and lateral to the subclavian artery, contains the neurovascular bundle of the C5, C6, and C7 nerve roots. The use of ultrasound to perform this block may decrease the volume of local anesthetic needed compared with using nerve stimulation.

Side effects associated with the interscalene block include hemidiaphragmatic paralysis, recurrent laryngeal nerve block, and Horner syndrome. ^, If larger volumes of local anesthetic are used, there are risks of contralateral, epidural, or intrathecal spread, leading to respiratory depression and possible loss of consciousness. The use of ultrasound may decrease the amount of local anesthetic needed for this block. ^, Despite concern for performing this block under general anesthesia due to risk of neurologic complications, a joint committee practice advisory from the European Society of Regional Anesthesia and Pain Therapy and the American Society of Regional Anesthesia and Pain Medicine stated that performing regional anesthesia in the pediatric population under general anesthesia or deep sedation was safe.

Indications, anatomy, and complications

The supraclavicular block, which is performed at the level of the divisions, provides analgesia to the upper arm, elbow, and hand. The divisions of the brachial plexus are located superficial and lateral to the subclavian artery ( Fig. 3 ). All roots of the brachial plexus are blocked at this location. However, the suprascapular nerve, which innervates the shoulder joint, may be spared.

Supraclavicular block. BP, brachial plexus; SA, subclavian artery.

Under ultrasound guidance, the probe is placed in the coronal-oblique plane just superior to the upper border of the midclavicle. The subclavian artery lies adjacent to the brachial plexus and appears hypoechoic and pulsatile. In an in-plane approach, the needle is directed medially toward the brachial plexus, which lies lateral and superior to the subclavian artery. This approach decreases the risk of intraneural injection as well as the risk of vascular injury.

Complications of this block include intravascular injection, infection, hematoma, and pneumothorax. The risk of pneumothorax may be higher than other brachial plexus blocks due to the proximity of the apex of the lung, which lies just medial to the first rib. An in-plane approach with visualization of the entire needle while performing this block may help prevent this complication.

Indications, anatomy, and complications

The infraclavicular block, similar to the supraclavicular block, is used for surgeries of the elbow, forearm, and hand. At this level, the cords of the brachial plexus are blocked. The cords are superficial to the axillary artery and veins and medial and inferior to the coracoid process ( Fig. 4 ). The pectoralis major and minor are located superficial to the brachial plexus. The medial cord can be difficult to visualize on ultrasound due to its location between the axillary artery and vein. This location is well suited for placement of brachial plexus catheters in children for prolonged analgesia. ^,

Infraclavicular block. AA, axillary artery; LC, lateral cord; MC, medial cord; PC, posterior cord; Pec major, pectoralis major muscle; Pec minor, pectoralis minor muscle.

In performing an ultrasound-guided infraclavicular block, the probe is placed inferior to the clavicle in a transverse orientation. The needle is directed laterally toward the cords and advanced using an out-of-plane technique. The local anesthetic is injected into the deep portion of the neurovascular sheath. Another technique, described by De José María and colleagues, places the probe parallel to the clavicle in a parasagittal plane, and the needle is directed toward the brachial plexus.

Complications related to infraclavicular blocks are similar to those of supraclavicular blocks. Vascular injury is also possible, given the proximity of the axillary artery and vein.

Indications, anatomy, and complications

The femoral nerve block is commonly used for surgeries of the knee. This block provides analgesia to the anterior thigh and knee and can be performed as a single-shot technique; a continuous catheter can be placed when longer-term pain relief is required. ^, The femoral nerve, originating from L2 to L4, is located deep to the fascia iliaca and lateral to the femoral artery and vein ( Fig. 5 ). On ultrasound, the neurovascular bundle is visualized with the probe placed in the inguinal crease. Given the risk of falls due to motor blockade, an alternative is to block the saphenous nerve, a branch of the femoral nerve, at the level of the adductor canal ( Fig. 6 ). The saphenous block can be performed proximally to provide sensory analgesia to the anterior knee or more distally to block sensation to the medial aspect of the lower leg.

Femoral nerve block. FA, femoral artery; FI, fascia iliaca; FN, femoral nerve.

Saphenous nerve block. FA, femoral artery; SM, sartorius muscle; SN, saphenous nerve.

For ultrasound-guided femoral nerve blocks, the probe is placed in the inguinal crease. The femoral artery is identified, and the nerve is visualized just lateral to the pulsating artery. The femoral vein should be visualized just medial to the artery. In contrast to the artery, it does not appear pulsatile and should be compressible. The needle should be placed at the lateral portion of the femoral nerve, using an in-plane or out-of-plane approach, with local anesthetic deposited to surround the nerve. ^, The saphenous nerve block is performed with the probe placed on the medial aspect of the thigh while the leg is abducted and laterally rotated. In an in-plane approach, the sartorius muscle is identified, and the needle is directed toward the saphenous nerve where local anesthetic is injected.

Complications for the femoral and saphenous nerve blocks include hematoma from vascular puncture, nerve injury, and infection.

Indications, anatomy, and complications

The sciatic nerve is blocked via the subgluteal, popliteal fossa, or anterior approach in children. ^, The nerve roots of L4 to S3 comprise the sciatic nerve. This nerve provides sensation to the posterior thigh as well as the distal leg; the medial compartment receives innervation from the femoral nerve. The nerve courses and exits the pelvis through the greater sciatic foramen and then travels inferiorly to the gluteus maximus muscle ( Fig. 7 ). It divides into the tibial and common peroneal nerves around the posterior popliteal fossa ( Fig. 8 ). This block may be performed as a single-shot or continuous catheter technique in the pediatric population. ^,

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