Brachial plexus block

Editor's Notes

• #7: Electrical nerve stimulation in regional anesthesia is a method of using a low-intensity (up to 5 mA) and short-duration (0.05-1 ms) electrical stimulus (at 1-2 Hz repetition rate) to obtain a defined response (muscle twitch or sensation) to locate a peripheral nerve or nerve plexus with an (insulated) needle. The goal is to inject a certain amount of local anesthetic in close proximity to the nerve to block nerve conduction and provide a sensory and motor block for surgery and/or, eventually, analgesia for pain management. The use of nerve stimulation can also help to avoid an intraneural intrafascicular injection and, consequently, nerve injury. Electrical nerve stimulation can be used for a single-injection technique, as well as for guidance during the insertion of continuous nerve block catheters. More recently, ultrasound (US) guidance and, in particular, the so-called dual guidance technique in which both techniques (peripheral nerve stimulation [PNS] and US) are combined, has become a common practice in many institutions.
• #9: CHOICE OF ANESTHETIC Local anesthetics are discussed elsewhere (see Chapter 14), but when performing a block, the anesthesiologist must weigh the toxicity of the agent to be used and the characteristics of individual local anesthetics such as time to onset and duration of action, degree of sensory versus motor block, and the cardiac toxicity of large volumes of local anesthetics delivered into the perineural sheath
• #10: Successful regional anesthesia of the upper extremity requires knowledge of brachial plexus anatomy from its origin, where the nerves emerge from the intervertebral foramina, to its termination in the peripheral nerves. Detailed anatomic knowledge enables the anesthesiologist to choose the appropriate technique for the intended surgical procedure and to salvage inadequate blocks by supplementation with local anesthetic. Without mastery of the anatomy, luck rather than skill becomes the primary determinant of successful neural blockade. Also important is an understanding of the side effects and complications of upper extremity regional techniques, as well as the clinical application of available local anesthetics for these blocks. The role of appropriate sedation during placement of the block and during the surgical procedure should not be underestimated. Many a “perfect” regional anesthetic technique has been undone by inadequate management of sedation.
• #11: Except for cutaneous supply to upper medial aspect of the arm and uppermost aspect of shoulder entire supply to the arm is by brachial plexus The brachial plexus is derived from the anterior primary rami of the fifth, sixth, seventh, and eighth cervical nerves and the first thoracic nerve, with variable contributions from the fourth cervical and second thoracic nerves. Between the scalene muscles, these nerve roots unite to form three trunks that emerge from the interscalene space to lie cephaloposterior to the subclavian artery as it courses along the upper surface of the first rib. The superior (C5 and C6), middle (C7), and inferior (C8 and T1) trunks are arranged accordingly and are not in a strict horizontal formation, as is often depicted. At the lateral edge of the first rib, each trunk forms anterior and posterior divisions that pass posterior to the midportion of the clavicle to enter the axilla. Within the axilla, these divisions form the lateral, posterior, and medial cords, named for their relationship with the second part of the axillary artery. The superior divisions from the superior and middle trunks form the lateral cord, the inferior divisions from all three trunks form the posterior cord, and the anterior division of the inferior trunk continues as the medial cord. At the lateral border of the pectoralis minor, the three cords divide into the peripheral nerves of the upper extremity. The lateral cord gives rise to the lateral head of the median nerve and the musculocutaneous nerve; the medial cord gives rise to the medial head of the median nerve, as well as the ulnar, the medial antebrachial, and the medial brachial cutaneous nerves; and the posterior cord divides into the axillary and radial nerves Aside from branches from the cords that form the peripheral nerves as described, several branches arising from roots of the brachial plexus provide motor innervation to the rhomboid muscles (C5), the subclavian muscles (C5 and C6), and the serratus anterior muscle (C5, C6, and C7). The suprascapular nerve arises from C5 and C6; it supplies the muscles of the dorsal aspect of the scapula and makes a significant contribution to the sensory supply of the shoulder joint.
• #12: After leaving their intervertebral foramina, these nerves course anterolaterally and inferiorly to lie between the anterior and middle scalene muscles, which arise from the anterior and posterior tubercles of the cervical vertebra, respectively. The anterior scalene muscle passes caudad and laterally and inserts into the scalene tubercle of the first rib; the middle scalene muscle inserts on the first rib posterior to the subclavian artery, which passes between these two scalene muscles along the subclavian groove. The prevertebral fascia invests the anterior and middle scalene muscles and fuses laterally to enclose the brachial plexus in a fascial sheath.
• #14: Relationships: vertebral A. travels cephalaud and enters bony canal ar C6. Ext. Jugular vein overlies the interscalene groove at C6. Over the first rib the divisions of B.P lie post., cephalaud and lat. To subclavain A. Axillary A. lies ant. To radial N., Postero medial to median nerve, Posterolateral to ulnar N. Cervical roots are just post. To vertebral A.
• #16: Blockade occurs at the level of the upper and middle trunks. Although this approach can also be used for forearm and hand surgery, blockade of the inferior trunk (C8 through T1) is often incomplete and requires supplementation at the ulnar nerve for adequate surgical anesthesia in that distribution In its course between the anterior and middle scalene muscles, the plexus is superior and posterior to the second and third parts of the subclavian artery. The dome of the pleura lies anteromedial to the inferior trunk
• #17: Blockade occurs at the level of the upper and middle trunks. Although this approach can also be used for forearm and hand surgery, blockade of the inferior trunk (C8 through T1) is often incomplete and requires supplementation at the ulnar nerve for adequate surgical anesthesia in that distribution.[ Supraclavicular nerve c3-4------ upper most part of shoulder Inntercostal T2 --- upper medial aspect of arm
• #18: This technique can be performed with the patient's arm in any position and is technically simple because of easy identification of the necessary landmarks.[14] The patient should be in the supine position with the head turned away from the side to be blocked. The posterior border of the sternocleidomastoid muscle is readily palpated by having the patient briefly lift the head. The interscalene groove may be palpated by rolling the fingers posterolaterally from this border over the belly of the anterior scalene muscle into the groove. A line extended laterally from the cricoid cartilage and intersecting the interscalene groove indicates 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. The use of a nerve stimulator or elicitation of paresthesias is recommended with this technique to accurately place the local anesthetic solution. After ordinary sterile precautions and development of a skin wheal, a 22- to 25-gauge, 4-cm needle is inserted perpendicular to the skin at a 45-degree caudad and slightly posterior angle ( Fig. 52-3 ). The needle is then advanced until a paresthesia (usually the C5 and C6 dermatomes) or nerve stimulator response is elicited, which usually occurs at a very superficial level. Paresthesia and motor response of the arm or shoulder are equally efficacious.[15] If a blunt needle bevel is used, a “click” may be detected as the needle passes through the prevertebral fascia. If bone is encountered within 2 cm of the skin, it is likely to be a transverse process, and the needle may be “walked” across this structure to locate the nerve. Likewise, contraction of the diaphragm indicates phrenic nerve stimulation and anterior needle placement; the needle should be redirected posteriorly to locate the brachial plexus. After the appropriate paresthesia or motor response is obtained, the needle is stabilized. The use of flexible extension tubing facilitates maintenance of the needle's position while aspiration and injection are taking place. After negative aspiration, 10 to 40 mL of solution is injected incrementally,
• #20: Ipsilateral phrenic nerve block resulting in diaphragmatic paresis occurs in 100% of patients undergoing interscalene blockade,[16] even with dilute solutions of local anesthetics, and is associated with a 25% reduction in pulmonary function. [17] [18] This effect probably results from anterior spread of solution over the anterior scalene muscle and may cause subjective symptoms of dyspnea. Although rare, respiratory compromise can occur in patients with severe respiratory disease. Involvement of the vagus, recurrent laryngeal, and cervical sympathetic nerves is rarely significant, but a patient experiencing symptoms related to these side effects may require reassurance. The incidence of pneumothorax is low when the needle is correctly placed at the C5 or C6 level because of the distance from the dome of the pleura. Severe hypotension and bradycardia (i.e., the Bezold-Jarisch reflex) have been reported in awake, sitting patients undergoing shoulder surgery under an interscalene block. The cause is presumed to be stimulation of intracardiac mechanoreceptors by decreased venous return, which produces an abrupt withdrawal of sympathetic tone and enhanced parasympathetic output. This effect results in bradycardia, hypotension, and syncope. The frequency of this reflex is decreased when prophylactic β-blockers are administered.[19] Nerve damage or neuritis can occur with any peripheral nerve block, but it is uncommon and is usually self-limited. Some surgical approaches to the shoulder, such as those for total-shoulder arthroplasty, are associated with neurologic risk to the brachial plexus. [20] [21] In such cases an interscalene block may be placed postoperatively for pain relief after the surgical service has ascertained and documented that no neurologic damage has occurred. Epidural and intrathecal injections have been reported with this block, a finding emphasizing the importance of inserting the needle in a caudad direction.[22] The proximity of significant neurovascular structures may increase the risk for serious neurologic complications when an interscalene block is performed in heavily sedated or anesthetized patients.[23] Several vascular structures are in proximity to a correctly placed needle. Local anesthetic toxicity as a result of intravascular injection should be guarded against by careful aspiration and incremental injection. Seizure activity from this complication is particularly undesirable after rotator cuff surgery because the repair can be compromised by the associated muscular activity.
• #21: Blockade occurs at the distal trunk–proximal division level. At this point, the brachial plexus is compact and a small volume of solution produces rapid onset of reliable blockade of the brachial plexus. An additional advantage is that the block can also be performed with the patient's arm in any position.
• #23: The patient is placed in a supine position with the head turned away from the side to be blocked. The arm to be anesthetized should be adducted, and the hand should be extended along the side toward the ipsilateral knee as far as possible a mark should be made approximately 1.5 to 2.0 cm posterior to the midpoint of the clavicle. Palpation of the subclavian artery at this site confirms the landmark. A 22-gauge, 4-cm needle is directed in a caudad, slightly medial, and posterior direction until a paresthesia or motor response is elicited or the first rib is encountered The goal of this block is to bring the tip of the needle in the proximity of the lower trunk, which is manifested by a twitch of the fingers in either flexion or extension. On localization of the brachial plexus, aspiration for blood should be performed before incremental injections of a total volume of 20 to 30 mL of solution.
• #25: Although the block is more difficult in obese patients, there does not appear to be an increased frequency of complications.[25] The prevalence of pneumothorax after a supraclavicular block is 0.5% to 6% and diminishes with experience. The onset of symptoms is usually delayed and may take up to 24 hours. Routine chest radiography after the block is not justified. The supraclavicular approach is best avoided when the patient is uncooperative or cannot tolerate any degree of respiratory compromise because of underlying disease. Other complications include frequent phrenic nerve block (40% to 60%), Horner's syndrome, and neuropathy. The presence of phrenic or cervical sympathetic nerve blockade normally requires only reassurance. Although nerve damage can occur, it is uncommon and usually self-limited.
• #26: Blockade occurs at the level of the cords and offers the theoretical advantages of avoiding pneumothorax while affording block of the musculocutaneous and axillary nerves. No special arm positioning is required. A nerve stimulator or ultrasound visualization is required because there are no palpable vascular landmarks to aid in directing the needle
• #28: The needle is inserted 2 cm below the midpoint of the inferior clavicular border and advanced laterally, and a nerve stimulator is used to identify the plexus. Incremental injection of 20 to 30 mL of solution is sufficient after the needle is correctly placed. The success rate is improved with a distal motor response
• #29: Patient position in needle insertion for infraclavicular brachial plexus block. The transducer is positioned parasagittally just medial to the coracoid process and inferior to the clavicle.
• #31: Blockade occurs at the level of the terminal nerves. Although blockade of the musculocutaneous nerve is not always produced with this approach
• #32: The axillary approach to the brachial plexus is the most popular because of its ease, reliability, and safety.[29], it can be supplemented at the level of the axilla or at the elbow. Indications for axillary block include surgery on the forearm and hand. Elbow procedures are also successfully performed with the axillary approach.[30] This block is ideally suited for outpatients and is easily adapted to the pediatric population.[31] However, an axillary block is unsuitable for surgical procedures on the upper part of the arm or the shoulder, and the patient must be able to abduct the arm to perform the block.
• #35: Needle insertions for axillary brachial plexus block. Axillary brachial block can be accomplished by two to four separate injections (1-4) to accomplish a block of the entire brachial plexus. MCN, musculocutaneous nerve;RN, radial nerve; MN, median nerve; UN, ulnar nerve.