Chapter 74 Brachial Plexus Blocks: Techniques Above the Clavicle

Question 1

The brachial plexus is formed by

Answer 1

the anterior primary rami of cervical nerve roots C5–C8 and thoracic nerve root T1.
The fourth cervical nerve (C4) contributes to about 67% of plexuses, and, if significant, may shift the plexus in a craniad
direction (“prefixed plexus”). The second thoracic nerve (T2) contributes to about 33% of plexuses, and may shift the plexus in a caudad direction (“postfixed plexus”).

Question 2

brachial plexus interact in a manner analogous to the components of a tree

Answer 2

roots, trunks, divisions, cords, and

terminal branches

Question 3

The roots of C5–C8 and T1 travel along the groove between

Answer 3

the anterior and posterior tubercles of the transverse processes of the cervical vertebrae,
pass posterior to the vertebral artery, and
descend toward the first rib

Question 4

“interscalene space”

Answer 4

they are enveloped

by the posterior fascia of the anterior scalene muscle and the anterior fascia of the middle scalene muscle

Question 5

The anterior scalene muscle arises from the

Answer 5

anterior tubercles of the
transverse processes of C3–C6 and inserts on the scalene tubercle of the first rib. It separates the subclavian vein and
artery

Question 6

The middle scalene muscle arises from the

Answer 6

posterior tubercles of the transverse processes of C2–C7 and inserts on the first rib just posterior to the subclavian groove
on the rib.

Question 7

After arriving at the distal end of their respective transverse
processes, the five roots converge to form the

Answer 7

three trunks (superior, middle, inferior), which together with the subclavian artery invaginate the scalene fascia to form
a “subclavian space.

Question 8

The superior trunk of the plexus is formed by the union of the

Answer 8

C5 and C6 nerve roots

Question 9

the middle trunk is the distal continuation of

Answer 9

C7

Question 10

the inferior trunk is formed by the union of the

Answer 10

C8 and T1 nerve roots

Question 11

As these three trunks pass over the first rib and under the clavicle, each divides into

Answer 11

an anterior and posterior division (there are a total of six divisions). It is at this level that separation of fibers destined for the anterior arm (flexor or volar surface of the
upper extremity) and the posterior arm (extensor or dorsal
surface) occurs.

Question 12

As the plexus emerges from beneath

the clavicle, the fibers recombine to form

Answer 12

the three cords

of the brachial plexus.

Question 13

The lateral cord is formed by the union of

Answer 13

the anterior divisions of the superior and middle

trunks.

Question 14

the medial cord is simply the continuation of the

Answer 14

anterior division of the inferior trunk

Question 15

the posterior

cord is composed of

Answer 15

the posterior divisions of all three trunks

Question 16

The medial and lateral cords then give rise to nerves that supply the

Answer 16

flexor surface of the upper extremity

Question 17

nerves arising from the posterior cord supply the

Answer 17

extensor surface of the arm

Question 18

The lateral and medial

cords give off branches that become

Answer 18

the lateral and medial

heads of the median nerve (C5–C8) (major terminal branch)

Question 19

The lateral cord continues as the

Answer 19

musculocutaneous

nerve (C5–C7) (major terminal branch)

Question 20

medial cord continues on as

Answer 20

the ulnar nerve (C7–T1)

major terminal branch

Question 21

The posterior cord gives off the

Answer 21

axillary nerve (C5–C6) (major terminal branch) and then continues on as the radial nerve (C5–T1) (major terminal
branch)

Question 22

The long thoracic nerve

Answer 22

arising from C5, C6, and C7, innervates the serratus anterior muscle.

Question 23

long thoracic nerve stimulation may result in

Answer 23

contraction of the muscular wall enveloping the ribs, and may be mistaken for diaphragmatic contraction resulting from stimulation of the phrenic nerve (C3,
C4, C5).

Question 24

dorsal scapular nerve

Answer 24

arising from C5 and
innervating the major and minor rhomboids and the levator scapulae, may be stimulated, resulting in a contraction of the musculature of the back and shoulder blade.

Question 25

The trunks also supply two branches

Answer 25

the nerve to the subclavius (C5–C6) and the suprascapular nerve (C5–C6).

Question 26

suprascapular nerve innervated

Answer 26

to motor branches to the supraspinatus and infraspinatus | muscles, it also supplies the only sensory fibers (to the shoulder joint) that arise above the clavicle

Question 27

As a general rule of thumb when using a nerve stimulator technique, diaphragmatic contraction requires

Answer 27

a more posterior reinsertion of the needle (the phrenic nerve is typically located outside the sheath on the anterior scalene muscle)

Question 28

trapezius or posterior deltoid contraction | requires

Answer 28

reinsertion of the needle more anteriorly | in the interscalene space

Question 29

Brachial plexus block

Answer 29

providing sensory analgesia and anesthesia and motor block, also blocks the sympathetic outflow to the upper extremity.

Question 30

Postganglionic | sympathetic nerve fibers reach the nerve roots as

Answer 30

gray rami communicantes from the middle and inferior cervical sympathetic ganglia and stellate ganglion. Additional contributions may arise from the vertebral artery (fibers given off to C4, C5, C6), and from the nerve of Kuntz (branch from T2)

Question 31

postganglionic fibers to the upper extremity are derived from two potential sources

Answer 31

The first is a distal innervation that is carried to the peripheral vessels by the somatic nerves of the plexus. The second mode is a proximal innervation (not extending beyond the proximal part of the brachial artery) arising from the cervical sympathetic chain, particularly via the stellate ganglion. This supplies the proximal one-third of the extremity.

Question 32

The distal innervation (distal two-thirds of the arm) mediates vasoconstriction of resistance vessels, implying that brachial plexus block produces

Answer 32

vasodilatation of veins | of the upper extremity, increases the amount of blood pooling in the distal arm, and increases skin temperature

Question 33

INTERSCALENE BLOCK TECHNIQUES

Answer 33

The patient lies supine with the head turned slightly toward the opposite side and is asked to relax the shoulder and reach with the hand on the affected side toward the ipsilateral knee. The interscalene groove is palpated posterior to the sternocleidomastoid muscle, and the C6 level is estimated by dropping a line laterally from the cricoid cartilage. With the palpating index and middle fingers straddling and indenting the interscalene groove (to minimize the distance from the skin to the cervical transverse processes), the opposite hand advances a short (1–2 inch) insulated needle into the groove, using nerve stimulator assistance. The direction of the needle should be perpendicular to the skin with a slightly posterior (dorsad), medial (mesiad), and inferior (caudad) direction until a motor response is observed at 0.5 mA or less

Question 34

When using PNS guidance for ISB, whereas an evoked motor response of the shoulder, elbow, or hand is acceptable prior to injecting local anesthetic, a shoulder paresthesia should

Answer 34

not be used as a sole endpoint since it may indicate that the stimulating needle is stimulating the suprascapular nerve, either within or outside the brachial plexus sheath

Question 35

resultant anesthesia | and analgesia of ISB

Answer 35

Blockade of C8 and T1 may not occur, and resultant anesthesia and analgesia will commonly be in the distribution of the nerve roots C5–C7. This block may provide complete surgical anesthesia for shoulder procedures and, if the surgeon is performing arthroscopy. the primary utility of ISB remains as a component of anesthesia for shoulder surgery

Question 36

In ISB, Due | to the proximity of the phrenic nerve

Answer 36

hemidiaphragmatic | paresis and concomitant 25% to 30% reduction in pulmonary function occurs routinely following this technique

Question 37

INTERSCALENE BLOCK US TECHNIQUES

Answer 37

the patient is positioned in similar fashion to traditional techniques or in the lateral decubitus position for in-plane needle guidance. When performing US-guided interscalene block techniques, the brachial plexus is identified in the short axis using a high-frequency linear transducer placed at or below the level of the cricoid cartilage in transverse orientation perpendicular to skin and posterior to the SCM muscle. The roots and trunks of the brachial plexus appear as hypoechoic structures between the fascia of the anterior and middle scalene muscles. Once the brachial plexus is identified, the block needle is inserted out-of-plane anterior to the interscalene groove or posterior to the US transducer in-plane aiming anteromedially. When the needle tip is positioned within the interscalene groove, local anesthetic solution is injected incrementally with real-time confirmation of appropriate injectate spread on US.

Question 38

Common long-acting local anesthetics chosen for single injection brachial plexus blocks include

Answer 38

racemic bupivacaine or levobupivacaine (the S (–) enantiomer of bupivacaine) with or without epinephrine, although some patients prefer to avoid the 18 to 30 hr of postblock paresis routinely seen with these agents. In these cases, one can use 1.5% mepivacaine, and additives such as clonidine or buprenorphine 0.3 mg/40 ml can be added to prolong postoperative analgesia

Question 39

Ropivacaine

Answer 39

an aminoamide local anesthetic that is highly protein bound and lipid soluble. as it is purported to have less propensity for cardiotoxicity than racemic bupivacaine, while having a similar anesthetic profile (in equipotent concentrations) for brachial plexus anesthesia

Question 40

Adjuvants given to augment postoperative analgesia. For prolonged postoperative analgesia,

Answer 40

clonidine 150 mg or buprenorphine | 300 mg may be added to the local anesthetic solution, or continuous catheter techniques may be used

Question 41

Gabapentin

Answer 41

used as a preemptive analgesic and administered in a single 800 mg dose orally before ISB for shoulder surgery

Question 42

Dexamethasone

Answer 42

8 mg

Question 43

single injection ISB | techniques, side effects like

Answer 43

hemidiaphragmatic paresis, Horner’s syndrome, and recurrent laryngeal nerve block are all possible using continuous catheter techniques, as are complications like hematoma, infection, nerve injury, hemopneumothorax, subcutaneous and mediastinal emphysema, and spinal subarachnoid and epidural block.

Question 44

The incidence of side effects like Horner’s syndrome, hoarseness, and subjective breathing difficulties related to the spread of local anesthetic to neural structures may be slightly higher following right-sided blocks than it is for left-sided interscalene brachial blocks.

Answer 44

The recurrent laryngeal nerve, on the right side, leaves the vagus nerve and loops around the subclavian artery several centimeters higher than the nerve on the left side, which does not emerge until the carotid has joined the aorta lower in the chest. This may explain the higher incidence of hoarseness on the right side versus the left. Alternatively, hoarseness may result from vasodilation of the larynx from local anesthetic spread to cervical sympathetic fibers.

Question 45

The syndrome of sudden hypotension and bradycardia (vasovagal syncope) during shoulder surgery with the patients in the beach-chair position is of continuing concern, and has been attributed to activation of

Answer 45

Bezold–Jarisch reflex

Question 46

SUPRACLAVICULAR BLOCK | associated with an incidence of

Answer 46

pneumothorax

Question 47

SUPRACLAVICULAR BLOCK TECHNIQUES

Answer 47

The patient lies supine with the shoulder completely relaxed and the head turned slightly toward the opposite side. The interscalene groove is palpated after the patient elevates the head off the bed to demonstrate the prominence of the clavicular head of the SCM muscle. The palpating finger(s) now sit on the anterior belly of the anterior scalene muscle, and must be rolled laterally toward the middle scalene muscle into the groove between the two muscles. The groove is traced inferiorly until the subclavian arterial pulse is felt, or until the omohyoid muscle (running obliquely and inferiorly across the groove) obscures further palpation. At the~ level of C6, a short (2-inch) insulated needle is advanced inferiorly (caudad, but not mesiad or dorsad). The needle is now in the longest dimension of the interscalene space (parallel to the scalene muscles), while observing the arm for an appropriate distal motor response at 0.5 mA or less. A total volume of 40 ml of local anesthetic solution is now injected in divided doses.

Question 48

The resultant anesthesia and analgesia of supraclavicular will be in the distribution of the

Answer 48

trunks (superior, middle, | inferior).

Question 49

SUPRACLAVICULAR BLOCK appropriate for

Answer 49

upper extremity surgeries at or below the shoulder.

Question 50

US-guided supraclavicular block

Answer 50

the patient is positioned in similar fashion to traditional supraclavicular block approaches, and a high-frequency linear or curvilinear US transducer is placed perpendicular to skin at the base of the interscalene groove just medial to the clavicle to image the brachial plexus in short axis. The neural elements of the brachial plexus appear posterolateral to the subclavian artery as hypoechoic round structures surrounded by hyperechoic connective tissue. Once the brachial plexus is identified, the block needle is inserted in-plane

Question 51

in supraclavicular block To ensure blockade of the C8 and T1 divisions for complete distal upper extremity anesthesia, local anesthetic injectate should be deposited in

Answer 51

the “corner pocket” between the posterolateral portion of | the subclavian artery and first rib

Question 52

supraclavicular block Compared to nerve stimulation techniques, US guidance may improve

Answer 52

procedural speed and minimize the occurrence of phrenic nerve block

Question 53

Perioperative nerve injury remains a significant concern following brachial plexus block

Answer 53

It has been suggested that perineural hematoma, intraneural edema, tissue reaction, or scar formation may be causative factors in neural injury. The roles of epinephrine-induced neural ischemia, intrafascicular (intraneuronal) injections, and chemical injury due to local anesthetics themselves as anesthetic factors in nerve injury have also been considered

Question 54

For ambulatory surgery, ISB as a single shot or continuous | infusion has been shown to provide

Answer 54

shot or continuous infusion has been shown to provide superior pain relief for rotator cuff repair and for total shoulder arthroplasty than that provided by use of systemic opioids and adjuvant medications

Question 55

parascalene techniques

Answer 55

advocate placing the needle across the interscalene space in its narrowest dimension. The slightest movement of the needle, therefore, may result in the needle exiting this space; hence a significant volume of local anesthetic could theoretically be deposited outside the intended fascial compartment.

Question 56

The interscalene block and supraclavicular block is carried | out at the level of the

Answer 56

The interscalene block is carried out at the level of the brachial plexus roots, while the supraclavicular block is carried out at the level of the nerve trunks or divisions.

Question 57

frequently missed following interscalene block

Answer 57

C8 and T1 nerve roots

Question 58

he most feared complication of the supraclavicular | block

Answer 58

risk of pneumothorax (estimated to be | 0.5% to 6%)