Orthopaedic Anesthesia - .Orthopaedic Anesthesia Part 2. Common Techniques of Regional Anesthesia

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Bulletin of the NYU Hospital for Joint Diseases 2008;66(4):306-16306

Latifzai K, Sites BD, Koval KJ. Orthopaedic anesthesia: Part 2. Common techniques of regional anesthesia in orthopaedics. Bull NYU Hosp Jt Dis. 2008;66(4):306-16.

Orthopaedic Anesthesia Part 2. Common Techniques of Regional Anesthesia in Orthopaedics

Khushal Latifzai, B.A., Brian D. Sites, M.D., and Kenneth J. Koval, M.D.

Abstract

Anesthesia may be considered in terms of two categories: general and regional. The aim of general anesthesia is to induce analgesia, sedation, amnesia, suppression of autonomic reflexes, and relaxation of muscles. Regional anesthesia is more site-specific and is typically divided into three categories based on the location of injection: 1. a central neuraxial block is an injection of an anesthetic drug into the epidural or intrathecal space; 2. a periph-eral nerve block is an injection near the nerve or plexus supplying the area under operation; and 3. a field block is an injection into the adjoining tissues with subsequent diffusion into the surgical area (in orthopaedics, it is typically employed for minor procedures of the hand or foot). Of these three categories of regional anesthesia (i.e., neuraxial, peripheral, and field blocks), this article focuses on the latter two. Although neuraxial blocks com-prise an important part of regional anesthesia, they are typically performed by anesthesiologists in an operative setting for major procedures of the lower extremities. The intent of this article is to familiarize the orthopaedist with techniques that have implications for emergency rooms and other ambulatory settings in which regional techniques are sometimes favored over general alterna-tives because they entail less risk of systemic side effects and may involve more cost-effective use of resources.

Anesthesia may be considered in terms of two cat-egories: general and regional. The aim of general anesthesia is to induce analgesia, sedation, amne-sia, suppression of autonomic reflexes, and relaxation of muscles. Regional anesthesia is more site-specific and is typically divided into three categories based on the loca-tion of injection: 1. central neuraxial block is injection of an anesthetic drug into the epidural or intrathecal space; 2. peripheral nerve block is injection near the nerve or plexus supplying the area under operation; and 3. field block is injection into the adjoining tissues, with subsequent diffu-sion into the surgical area (in orthopaedics, it is typically employed for minor procedures of the hand or foot). Of the three categories of regional anesthesia (i.e., neur-axial, peripheral, and field blocks), this article will focus on the latter two. Although neuraxial blocks comprise an important part of regional anesthesia, they are typically performed by anesthesiologists in an operative setting for major procedures of the lower extremities. The intent of this article is to familiarize the orthopaedist with techniques that have implications for the emergency room and other ambula-tory settings, in which regional techniques are sometimes favored over general alternatives, as they entail less risk for systemic side effects and may involve more cost-effective use of resources.

Peripheral Blocks of the Upper ExtremitiesAnatomy The brachial plexus is the neural supply to the upper extremi-ties. A thorough understanding of its anatomical structure is essential for the clinician to apply the appropriate regional anesthetic technique (Fig. 1). An overview of the brachial plexus and its layout includes the following. Anterior primary rami of the C5-T1 spinal nerves give rise to five nerve roots that travel anterolaterally and inferiorly to pass between the anterior and middle scalene muscles. Once in

Khushal Latifzai, B.A., and Kenneth J. Koval, M.D., Professor of Orthopaedic Surgery, are from the Department of Orthopaedics, Dartmouth-Hitchcock Medical Center. Brian D. Sites, M.D., is and Associate Professor of Anesthesiology, in the Department of Anesthesia, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire. Correspondence: Kenneth J. Koval, M.D., Dartmouth Hitchcock Medical Center, 1 Medical Center Drive, Lebanon, New Hampshire 03766; kjkmd@yahoo.com.

307Bulletin of the NYU Hospital for Joint Diseases 2008;66(4):306-16

the interscalene space, the roots merge into the superior (C5-C6), middle (C7), and inferior (C8-T1) trunks. Each one of these three trunks separates into an anterior and posterior

division (for a total of six divisions) at the level of the first rib (in some texts, the anterior and posterior divisions of each trunk are referred to as the superior and inferior divi-sions, respectively). The six divisions continue into the axilla, where they unite in various combinations to yield a total of three cords that are named in accordance with their relationship to the second part of the axillary artery. Details of this division-to-cord transition are as follows: the anterior divisions of the superior and middle trunks combine to produce the lateral cord; the posterior divisions of all three trunks unite, forming the posterior cord; and the anterior division of the inferior trunk continues on as the medial cord. The next transition, from the three cords to peripheral branches, occurs at the lateral border of the pectoralis minor. The lateral cord contributes to the formation of two peripher-al nerves: it alone gives rise to the musculocutaneous nerve, and it also combines with the medial cord to establish the median nerve. In addition to its contribution to the median nerve, the medial cord generates the ulnar, antebrachial, and medial brachial cutaneous nerves. And finally, the posterior cord splits into the axillary and radial nerves. Important departures from the pattern of transition of the brachial plexus thus outlined are several branches that emanate directly from the roots (instead of cords). These

Figure 1 Anatomy of the brachial plexus. (Reproduced from: Campbells Operative Orthopaedics. (10th ed). Copyright 2003 Mosby, Inc., with permission.)

Table 1 Plexus Blocks of the Upper Extremities

Technique Neural Target/Indications Comments

Interscalene Block Target: Root-to-trunk Injection Volume: 10-15 mL transition (interscalene space). (ultrasound); otherwise, 20-40 mL. Indications: Proximal procedures of arm; requires supplementation with ulnar nerve block for procedures of forearm and hand.

Supraclavicular Block Target: Trunk-to-division Injection Volume: 10-15 mL (ultrasound transition. highly desirable; if unavailable, use Indications: Procedures of infraclavicular block). the arm, elbow, or forearm.

Infraclavicular Block Target: Posterior, lateral, and Injection Volume: 7-11 mL per neural medial cords. cord (ultrasound); otherwise, one 20-30 mL) injection. Indications: Procedures of the Compared with axillary block, has elbow, forearm, and hand. advantage of not requiring supplemental injection of musculocutaneous nerve. If ultrasound and nerve stimulation are unavailable unavailable, forego above advantage, and use axillary block.

Axillary Block Target: Radial, ulnar, and median Injection Volume: 5-8 mL per nerve nerves. (ultrasound). If ultrasound is unavailable, Indications: Procedures of elbow, several options still exist: 35-40 mL (single forearm, and hand. injection); 10 mL (near each of the three nerves); two 20 mL injections (transarterial approach); or 40-50 mL (fascial click method). Compared with infraclavicular block, can be performed in the absence of ultrasound or nerve stimulation. Requires supplemental injection of musculocutaneous nerve.

Bulletin of the NYU Hospital for Joint Diseases 2008;66(4):306-16308

branches primarily supply motor functions to muscles of the axial skeleton (e.g., serratus anterior, rhomboids, etc.). However, the suprascapular nerve (C5-C6) provides sensa-tion to the shoulder joint in addition to its motor functions. Of the brachial plexus blocks, the interscalene approach is the only one to anesthetize the suprascapular nerve. Therefore, it is the most appropriate block for procedures involving the shoulder.

Interscalene BlockBest suited for procedures involving the most proximal as-pects of the arm (e.g., the shoulder), this block is directed at the root-to-trunk transition of the brachial plexus occurring in the interscalene space, at the level of the C6 vertebra. The result is a blockade of the superior and middle trunks (C5-C7), as well as the suprascapular nerve (C5-C6). Be-cause the inferior trunk (C8-T1) is not entirely anesthetized with this approach, it is not indicated for procedures of the forearm and hand unless supplemented with an ulnar nerve block (Table 1).

Supraclavicular BlockApplied at the level of the supraclavicular fossa, this ap-proach targets the transition of the three brachial plexus trunks into their respective divisions. The supraclavicular block is indicated for procedures of the arm, elbow, or forearm. Because of the proximity of the cervical pleura, ultrasound visualization is highly recommended (Fig. 2). If ultrasound tools are unavailable, then the infraclavicular approach should be considered, because the latter poses less risk of a pneumothorax (Table 1).1

Infraclavicular BlockApplied at the level of three cords (medial, lateral, and posterior) of the brachial plexus, this approach is indicated for procedures involving areas from the distal arm to the hand. Blockade of the musculocutaneous nerve gives this

approach an advantage over the axillary block. However, in the absence of ultrasound, while this technique relies on a nerve stimulator to guide the needle, the axillary block can be employed using a palpable vascular landmark, making the latter a simpler technique to administer (Table