Upper extremity regional anesthesia: essentials of our current understanding, 2008

Abstract

Brachial plexus blockade is the cornerstone of the peripheral nerve regional anesthesia practice of most anesthesiologists. As part of the American Society of Regional Anesthesia and Pain Medicine's commitment to providing intensive evidence-based education related to regional anesthesia and analgesia, this article is a complete update of our 2002 comprehensive review of upper extremity anesthesia. The text of the review focuses on (1) pertinent anatomy, (2) approaches to the brachial plexus and techniques that optimize block quality, (4) local anesthetic and adjuvant pharmacology, (5) complications, (6) perioperative issues, and (6) challenges for future research.

FIGURE 1

Dissection of the right brachial plexus. The vertebral artery (VA) is medial to the anterior scalene muscle (AS) and travels anterior to the plexus before entering the canal formed by the vertebral transverse process. The phrenic nerve (PN) overlies the anterior scalene muscle. The C5 and C6 nerve roots join to form the upper trunk. MS indicates middle scalene muscle; SA, subclavian artery; SSN, suprascapular nerve; C8, C8 nerve root. Dissection and photo courtesy of Carlo D. Franco, MD. Modified with permission from Franco and Clark. Tech Reg Anesth Pain Manag. 2008;12:134 (Elsevier).

FIGURE 2

Dissection of the right interscalene area. The brachial plexus is contained within connective tissue and traverses between the anterior (AS) and middle scalene (MS) muscles. The plexus is lateral to the subclavian artery (SA). SCM indicates sternocleidomastoid muscle. Photo courtesy of Quinn H. Hogan, MD.

FIGURE 3

Cryomicrotome section of the left neck at the C7 level. The brachial plexus (BP) lies between the anterior (AS) and middle scalene (MS) muscles. Note the closeness of the brachial plexus to the skin and to the vertebral canal and its contents. SCM indicates sternocleidomastoid muscle; J, jugular vein; C, carotid artery. Cryomicrotome courtesy of Quinn H. Hogan, MD.

FIGURE 4

Idealized brachial plexus. Various approaches define individual brachial plexus blocks and their expected distribution of cutaneous anesthesia. Illustration by Jennifer Gentry. ©American Society of Regional Anesthesia and Pain Medicine.

FIGURE 5

Peripheral nerve anatomy. Nerves are a collection of individual axons, which are surrounded by loose endoneurium and freely interdigitate along their course (12-o′clock). Axons receive nutrition from intrinsic vessels. Extrinsic vessels supply the intrinsic system and are under adrenergic control. Fascicles are collections of axons contained within perineurium. Fascicles are separated by connective tissue and surrounded by epineurium. Illustration by Jennifer Gentry. ©American Society of Regional Anesthesia and Pain Medicine.

FIGURE 6

Cutaneous sensory distribution of the upper extremity. Terminal nerves of the brachial plexus provide sensory innervation to the arm. The sensory distribution of these nerves is variable and overlapping—as depicted by blended colors as the zones converge. Illustration by Jennifer Gentry. ©American Society of Regional Anesthesia and Pain Medicine.

FIGURE 7

Cryomicrotome section of the right supraclavicular area. The brachial plexus (arrows) lies posterior and lateral to the subclavian artery (SA). Note the proximity of the lung. There is no evidence of a defined brachial plexus sheath in this section. Cryomicrotome courtesy of Quinn H. Hogan, MD.

FIGURE 8

Axillary block. Top left insert depicts the expected distribution of anesthesia consequent to AXB. The 4 terminal nerves are drawn in their classic relationship to the axillary artery, which in turn is correlated to ultrasonic anatomy that shows the hyperechoic nerves. Note: To correlate with the illustration, the ultrasound inset is rotated 90 degrees clockwise from the way it is normally viewed in a patient. There is significant variation in how the terminal nerves relate to the axillary artery. The upper right inset depicts these variations as color-coded nerves in various positions around the artery (radial nerve = orange, ulnar nerve = blue, median nerve = green). The color saturation correlates with the expected frequency of the nerve residing in a specific location—the deeper the saturation, the more frequently the nerve is found in that position. The musculocutaneous nerve (MC) lies in the fascial plane between the coracobrachialis and biceps muscles. Illustration by Jennifer Gentry. ©American Society of Regional Anesthesia and Pain Medicine.

FIGURE 9

Dissection of the right axilla. The brachial plexus is contained within connective tissue of the axillary sheath and lies inferior to the biceps and coracobrachialis muscles. At this level, the musculocutaneous nerve is likely within the belly of the coracobrachialis muscle or the fascial plane between it and the biceps. Note that the intercostobrachial nerve is not part of the plexus. Photo courtesy of Quinn H. Hogan, MD.

FIGURE 10

Interscalene block. The upper left inset depicts the expected distribution of anesthesia consequent to ISB. The roots converge to form trunks at the medial border of the middle scalene muscle. The vertebral artery lies medial to the anterior scalene muscle and anterior to the plexus. The classic ultrasound view depicts the hypoechoic upper roots (most likely C5–C7) stacked on each other, within the interscalene groove. The upper right inset depicts the closeness of the brachial plexus to major arteries and the spinal canal. Illustration by Jennifer Gentry. ©American Society of Regional Anesthesia and Pain Medicine.

FIGURE 11

Supraclavicular block. Inset depicts the expected distribution of anesthesia consequent to supraclavicular block. The trunks begin to diverge into the anterior and posterior divisions as the brachial plexus courses below the clavicle and over the first rib. The plexus is posterior and lateral to the subclavian artery, and both overlie the first rib in close approximation to the pleura and lung. The classic ultrasound view depicts the hypoechoic trunks bundled together lateral to the subclavian artery and over the first rib, which casts an acoustic shadow as the ultrasound beam is attenuated by bone. Note that the pleura does not impede the passage of the ultrasound beam to the same extent. Illustration by Jennifer Gentry. ©American Society of Regional Anesthesia and Pain Medicine.

FIGURE 12

Infraclavicular block. Inset depicts the expected distribution of anesthesia consequent to ICB. The cords take on their characteristic position lateral, posterior, and medial to the second part of the axillary artery in this illustration of the coracoid approach. The medial cord frequently lies between the axillary artery and vein (4-o′clock). There is considerable variation in the relationship of the artery to the cords, as depicted by the color-coded cords in the upper right inset (lateral cord = green, medial cord = blue, posterior cord = orange). The color saturation correlates with the expected frequency of the cord residing in a specific location—the deeper the saturation, the more frequently the cord is found in that position. Illustration by Jennifer Gentry. ©American Society of Regional Anesthesia and Pain Medicine.

FIGURE 13

Block of the supraclavicular branches of the superficial cervical plexus. Inset depicts the expected distribution of anesthesia consequent to supraclavicular nerve block. The 3 supraclavicular nerve branches (C3–C4) provide cutaneous innervation to the cape of the shoulder. Illustration by Jennifer Gentry. ©American Society of Regional Anesthesia and Pain Medicine.

FIGURE 14

Suprascapular nerve block. Inset depicts the expected distribution of anesthesia consequent to SSNB—the posterior 70% of the shoulder joint and the acromioclavicular joint. The nerve exits through the suprascapular notch. A cephalad-to-caudad needle trajectory (arrow) should reduce the risk of entering the notch and causing a pneumothorax. Illustration by Jennifer Gentry. ©American Society of Regional Anesthesia and Pain Medicine.

FIGURE 15

Medial and lateral antebrachial cutaneous nerve blocks. The medial antebrachial cutaneous nerve branches from the medial cord to innervate the ulnar volar forearm. The lateral antebrachial cutaneous nerve is the sensory terminus of the musculocutaneous nerve; it innervates the radial volar forearm. Illustration by Jennifer Gentry. ©American Society of Regional Anesthesia and Pain Medicine.

FIGURE 16

Percent of maximal rat sciatic nerve injury as a function of time, and needle bevel type and orientation. Nerve injury is determined by the cumulative score of 3 graded components: intraneuronal disruption (graded 0 to 5), axonal degeneration (graded yes/no), and disorganized fiber regeneration (graded yes/no). Nerve lesions induced by short-bevel needles are more severe and take longer to repair than those induced by long-bevel needles. Nerve injury induced by short-bevel needle was often associated with persisting signs of injury 28 days after the injury. LB(p) indicates long-bevel needle in parallel configuration to nerve fibers; LB(t), long-bevel needle in transverse configuration to nerve fibers; SB(p), short-bevel needle in parallel configuration to nerve fibers; SB(t), short-bevel needle in transverse configuration to nerve fibers. Reproduced by permission of Oxford University Press/British Journal of Anaesthesia.

FIGURE 17

Mechanisms of peripheral nerve injury. Direct needle trauma can rarely lacerate a nerve (A) or, more typically, injure the perineurium (B) and thereby expose the axons to potential local anesthetic neurotoxicity (shaded area). Vasoconstrictors may worsen injury by reducing local anesthetic clearance (inset). Illustration by Gary J. Nelson. Reproduced with permission from Neal and Rathmell. Complications in Regional Anesthesia and Pain Medicine (Elsevier Saunders).

FIGURE 18

Mechanisms of phrenic nerve blockade. Hemidiaphragmatic paresis occurs as a consequence of phrenic nerve blockade during brachial plexus blocks. The phrenic nerve can be blocked as local anesthetic moves cephalad to the C3–C4 nerve roots (shading), as the phrenic nerve passes nearby the C5 nerve root, or as the phrenic nerve courses along the anterior scalene muscle. Illustration by Gary J. Nelson. Reproduced with permission from Neal and Rathmell. Complications in Regional Anesthesia and Pain Medicine (Elsevier Saunders).

FIGURE 19

Mechanisms of unintended neuraxial block during interscalene brachial plexus anesthesia. The spinal canal and its contents are within 35 mm of the skin in most patients and can be accessed by unintentionally deep needle placement. Needles can also enter long dural root cuffs, thereby accessing cerebrospinal fluid (inset). Illustration by Gary J. Nelson. Reproduced with permission from Neal and Rathmell. Complications in Regional Anesthesia and Pain Medicine (Elsevier Saunders).

FIGURE 20

Mechanisms of cervical sympathetic trunk anesthesia. The stellate ganglia is quite close to the brachial plexus. Diffusion of local anesthetic from properly placed needles near the brachial plexus can unintentionally anesthetize the stellate ganglia (arrow) and cause Horner syndrome. Illustration by Gary J. Nelson. Reproduced with permission from Neal and Rathmell. Complications in Regional Anesthesia and Pain Medicine (Elsevier Saunders).

FIGURE 21

Mechanisms of recurrent laryngeal nerve anesthesia. The recurrent laryngeal nerve and vagus nerve can be unintentionally anesthetized during the course of brachial plexus regional anesthesia. Local anesthetic diffuses or tracks through tissue planes (arrows) and causes hoarseness during the blockade′s duration. Illustration by Gary J. Nelson. Reproduced with permission from Neal and Rathmell. Complications in Regional Anesthesia and Pain Medicine (Elsevier Saunders).

FIGURE 22

Mechanisms of hypotension/bradycardia. Patients who receive interscalene brachial plexus block, are sedated, and are placed in the beach-chair position may develop hypotension and bradycardia during their anesthetic course. The proposed mechanism for this phenomenon is a relative preload deficit from the sitting position, combined with a hypercontractile ventricle, which occurs as a consequence of exogenous and endogenous epinephrine. The vigorously contracting “empty” heart causes reflex bradycardia and hypotension. Illustration by Gary J. Nelson. Reproduced with permission from Neal and Rathmell. Complications in Regional Anesthesia and Pain Medicine (Elsevier Saunders).