Chapter 74 Brachial Plexus Blocks: Techniques Above the Clavicle Flashcards Preview

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Flashcards in Chapter 74 Brachial Plexus Blocks: Techniques Above the Clavicle Deck (58):

The brachial plexus is formed by

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”).


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

roots, trunks, divisions, cords, and
terminal branches


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

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


“interscalene space”

they are enveloped
by the posterior fascia of the anterior scalene muscle and the anterior fascia of the middle scalene muscle


The anterior scalene muscle arises from the

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


The middle scalene muscle arises from the

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


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

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


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

C5 and C6 nerve roots


the middle trunk is the distal continuation of



the inferior trunk is formed by the union of the

C8 and T1 nerve roots


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

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.


As the plexus emerges from beneath
the clavicle, the fibers recombine to form

the three cords
of the brachial plexus.


The lateral cord is formed by the union of

the anterior divisions of the superior and middle


the medial cord is simply the continuation of the

anterior division of the inferior trunk


the posterior
cord is composed of

the posterior divisions of all three trunks


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

flexor surface of the upper extremity


nerves arising from the posterior cord supply the

extensor surface of the arm


The lateral and medial
cords give off branches that become

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


The lateral cord continues as the

nerve (C5–C7) (major terminal branch)


medial cord continues on as

the ulnar nerve (C7–T1)
(major terminal branch)


The posterior cord gives off the

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


The long thoracic nerve

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


long thoracic nerve stimulation may result in

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).


dorsal scapular nerve

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.


The trunks also supply two branches

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


suprascapular nerve innervated

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


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

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


trapezius or posterior deltoid contraction

reinsertion of the needle more anteriorly
in the interscalene space


Brachial plexus block

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


sympathetic nerve fibers reach the nerve roots as

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)


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

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.


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

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



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


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

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


resultant anesthesia
and analgesia of ISB

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


In ISB, Due
to the proximity of the phrenic nerve

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



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.


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

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



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


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

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



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



8 mg


single injection ISB
techniques, side effects like

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.


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.

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.


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

Bezold–Jarisch reflex


associated with an incidence of




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.


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

trunks (superior, middle,



upper extremity surgeries at or below the shoulder.


US-guided supraclavicular block

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


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

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


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

procedural speed and minimize the occurrence of phrenic nerve block


Perioperative nerve injury remains a significant concern following brachial plexus

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


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

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


parascalene techniques

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.


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

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.


frequently missed following interscalene block

C8 and T1 nerve roots


he most feared complication of the supraclavicular

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

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