NYSORA - The New York School of Regional Anesthesia: Ultrasound-Guided Interscalene Brachial Plexus Block

Ultrasound-Guided Interscalene Brachial Plexus Block
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admin on 06/08/2013 02:30:00


Figure 1: Ultrasound-guided interscalene brachial plexus block; transducer and
needle position to obtain the desired ultrasound image for an in-plane approach.
Essentials
Indications: shoulder and upper arm surgery
Transducer position: transverse on neck, 3-4 cm superior to clavicle, over
external jugular vein
Goal: local anesthetic spread around superior and middle trunks of brachial
plexus, between anterior and middle      scalene muscles
Local anesthetic: 15-25 mL
General Considerations
Figure 2: Relevant anatomy for interscalene brachial block and transducer
position to obtain the desired views. Brachial plexus (BP) is seen sandwiched
between middle scalene muscle (MSM) laterally and anterior scalene muscle (ASM)
medially. Ultrasound image often includes a partial view of the lateral border
of the sternocleidomastoid muscle (SCM) as well as the internal jugular vein
(IJV) and carotid artery (CA). The transverse process of one of the cervical
vertebrae is also often seen.
The ultrasound-guided technique of interscalene brachial plexus block differs
from nerve stimulator or landmark-based techniques in several important aspects.
Most importantly, distribution of the local anesthetic is visualized to assure
adequate spread around the brachial plexus. Ultrasound guidance allows multiple
injections around the brachial plexus, therefore eliminating the reliance on a
single large injection of local anesthetic for block success as is the case with
non-ultrasound-guided techniques. Ability to inject multiple aliquots of local
anesthetic also may allow for the reduction in the volume of local anesthetic
required to accomplish the block. Repetition of the block in case of inadequate
anesthesia is also possible, a management option that is unpredictable without
ultrasound guidance. Finally, the risk of major vessel and nerve puncture during
nerve block performance is reduced.
Ultrasound Anatomy
The brachial plexus at the interscalene level is seen lateral to the carotid
artery, between the anterior and middle scalene muscles (Figures 2, 3, and 4).
Prevertebral fascia, superficial cervical plexus and sternocleidomastoid muscle
are seen superficial to the plexus. The transducer is moved in the
superior-inferior direction until two or more of the brachial plexus trunks are
seen in the space between the scalene muscles. Depending on the depth of field
selected and the level at which the scanning is performed, first rib and/or apex
of the lung may be seen. The brachial plexus is typically visualized at a depth
of 1 to 3 cm.
Distribution of Blockade
The interscalene approach to brachial plexus blockade results in anesthesia of
the shoulder and upper arm. Inferior trunk for more distal anesthesia can also
be blocked by additional, selective injection, deeper in the plexus. This is
accomplished either by controlled needle redirection inferiorly or by additional
scanning to visualize the inferior trunk and another needle insertion and
targeted injection.
Figure 3: Interscalene brachial plexus is seen between middle scalene muscle
and anterior scalene muscle. Carotid artery is seen medial at 1 cm depth in this
image.
Figure 4: Typical image of the brachial plexus (BP). The BP is seen positioned
between the anterior scalene muscle (ASM) and the middle scalene muscle (MSM).
The superficial cervical plexus (white arrowhead) can be seen posterior to the
SCM and underneath the prevertebral fascia. In this particular image, the
vertebral artery (VA), carotid artery (CA), as well as the transverse process of
C6 are also seen.
Equipment
Equipment needed includes the following:
Ultrasound machine with linear transducer (8-14 MHz), sterile sleeve, and gel
Standard nerve block tray
One 20-mL syringe containing local anesthetic
5-cm, 22-gauge short-bevel insulated stimulating needle
Peripheral nerve stimulator
Sterile gloves
Landmarks and Patient Positioning
Any position that allows comfortable placement of the ultrasound transducer and
needle advancement is appropriate. The block is typically performed with the
patient in supine, semisitting, or semilateral decubitus position, with the
patient's head facing away from the side to be blocked. The latter position may
prove ergonomically more convenient, especially during an in-plane approach from
the lateral side, in which the needle is entering the skin at the posterolateral
aspect of the neck. A slight elevation of the head of the bed is often more
comfortable for the patient, and it allows for better drainage and less
prominence of the neck veins.
Adherence to strict anatomic landmarks is of lesser importance for the
ultrasound-guided interscalene block than it is the case for the surface
anatomy-based techniques. Regardless, knowledge of the underlying anatomy and
the position of the brachial plexus is important to facilitate recognition of
the ultrasound anatomy. Scanning usually begins just below the level of the
cricoid cartilage and medial to the sternocleidomastoid muscle with a goal to
identify the carotid artery.
GOAL
The goal is to place the needle in the tissue space between the anterior and
middle scalene muscles and inject local  anesthetic until the spread around the
brachial plexus is documented by ultrasound. The volume of the local anesthetic
and  number of needle insertions are determined during the procedure and depend
on the adequacy of the observed spread of  the local anesthetic.
Technique
With the patient in the proper position, the skin is disinfected and the
transducer is positioned in the transverse plane to identify the carotid artery
(Figure 5). Once the artery is identified, the transducer is moved slightly
laterally across the neck (see algorithm at end of chapter). The goal is to
identify the scalene muscles and the brachial plexus that is sandwiched between
the anterior and middle scalene muscles.
The needle is then inserted in-plane toward the brachial plexus, typically in a
lateral-to-medial direction (Figure 7), although medial-to-lateral needle
orientation also can be chosen if more convenient. As the needle passes through
the prevertebral fascia, a certain "give" is often appreciated. When nerve
stimulation is used (0.5 mA, 0.1 msec), the entrance of the needle in the
interscalene groove is often associated with a motor response of the shoulder,
arm, or forearm as another confirmation of the proper needle placement. After a
careful aspiration to rule out an intravascular needle placement, 1 to 2 mL of
local anesthetic is injected to document the proper needle placement (Figure
8A). Injection of several milliliters of local anesthetic often displaces the
brachial plexus away from the needle.
An additional advancement of the needle 1 to 2 mm toward the brachial plexus
may be beneficial to assure a proper spread of the local anesthetic (Figure 8B).
Whenever the needle is further advanced, or multiple injections used, assure
that high resistance to injection is absent to decrease the risk of an
intrafascicular injection. When injection of the local anesthetic does not
appear to result in a spread around the brachial plexus, additional needle
repositions and injections may be necessary.
In an adult patient, 15 to 25 mL of local anesthetic is usually adequate for
successful and rapid onset of blockade. Smaller volumes of local anesthetics can
also be effective, however, their success rate in everyday clinical practice may
be inferior to those reported in meticulously conducted clinical trials.
NYSORA Highlights
When the visualization of the brachial plexus between the scalene muscles
proves difficult, the transducer is lowered to      the supraclavicular fossa.
At this position, the brachial plexus is identified lateral and superficial to
the subclavian artery,      (Figure 6). From here, the brachial plexus is traced
cranially to the desired level.
Figure 5: Ultrasound image just below the level of the cricoid cartilage and
medial to the sternocleidomastoid muscle. ASM, anterior scalene muscle; SCM,
sternocleidomastoid muscle; IJV, internal jugular vein; CA, carotid artery; Th,
thyroid gland.
Figure 6: View of the brachial plexus (BP) at the supraclavicular fossa. When
identification of the brachial plexus at the interscalene level proves
difficult, the transducer is positioned at the supraclavicular fossa to identify
the BP superficial and lateral to the subclavian artery (SA). The transducer is
then slowly moved cephalad while continuously visualizing the brachial plexus
until the desired level is reached.
NYSORA Highlights
The presence of the motor response to nerve stimulation is useful but not
necessary to elicit if the plexus, needle, and       local anesthetic spread are
well-visualized.
The neck is a very vascular area, and care must be exercised to avoid needle
placement or injection into the vascular       structures. Of particular
importance is to avoid the vertebral artery, and branches of the thyrocervical
trunk: inferior thyroid       artery, suprascapular artery, and transverse
cervical artery.
Never inject against high resistance (>15 psi) because this may indicate a
needle-nerve contact or an intrafascicular       injection.
Pro and con of multiple injections:
Pro: May increase the speed of onset and success rate of the interscalene
block.
Pro: May allow for a reduction in the total volume and dose of local anesthetic
required to accom- plish block.
Con: May carry a higher risk of nerve injury because part of the plexus may be
anesthetized by the time consecutive       injections are made.
NOTE: Avoidance of high resistance to injection and needle-nerve contact is
essential to avoid intrafascicular injection       because reliance on nerve
stimulation with multiple injections is diminished.
A
A
B
B
Figure 7: (A) Transducer placement and needle insertion. (B) The desired
position of the needle (1) for the interscalene brachial plexus block using an
in-plane approach. The needle tip is seen in contact with the superior trunk of
the brachial plexus (yellow arrows); this always results in high injection
pressure (>15 psi)-indicating that the needle should be withdrawn slightly away
from the trunk.
Figure 8: (A) A small amount of local anesthetic (blue shaded area) is injected
through the needle to confirm the proper needle placement. A properly placed
needle tip will result in distribution of the local anesthetic between and/or
alongside roots of the brachial plexus (BP). (B) An actual needle (white
arrowhead) placement in the interscalene groove with the dispersion of the local
anesthetic (LA; blue shaded area or arrows) surrounding the BP.
Continuous Ultrasound-Guided Interscalene Block
The goal of the continuous interscalene block is similar to the
non-ultrasound-based techniques: to place the catheter in the vicinity of the
trunks of the brachial plexus between the scalene muscles. The procedure
consists of three phases: needle placement, catheter advancement, and securing
of the catheter. For the first two phases of the procedure, ultrasound can be
used to assure accuracy. The needle is typically inserted in-plane from the
lateral-to-medial direction and underneath the prevertebral fascia to enter the
interscalene space (Figure 9), although other needle directions could be used.
Figure 9: Continuous brachial plexus block. Needle is inserted in the
interscalene space using an in-plane approach. Please note that for better
demonstration, sterile drapes are not used in the model in this figure.
Figure 10: An ultrasound image demonstrating needle and catheter (white arrow)
inserted in the interscalene space between the anterior (ASM) and middle (MSM)
scalene muscles. BP, brachial plexus.
Proper placement of the needle can also be confirmed by obtaining a motor
response of the deltoid muscle, arm, or forearm (0.5 mA, 0.1 msec) at which
point 4 to 5 mL of local anesthetic can be injected. This small dose of local
anesthetic serves to assure adequate distribution of the local anesthetic as
well as to make the advancement of the catheter more comfortable to the patient.
This first phase of the procedure does not significantly differ from the
single-injection technique. The second phase of the procedure involves
maintaining the needle in the proper position and inserting the catheter 2 to 3
cm into the interscalene space in the vicinity of the brachial plexus (Figure
10). Insertion of the catheter can be accomplished by a single operator or with
a helper. Proper location of the catheter can be determined either by
visualizing the course of the catheter or by an injection of the local
anesthetic through the catheter. When this proves difficult, alternatively, a
small amount of air (1 mL) can be injected to confirm the catheter tip location.
There is no agreement on what constitutes the ideal catheter securing system.
The catheter is secured by either taping to the skin or tunneling. Some
clinicians prefer one over the other. However, the decision about which method
to use could be based on the patient's age, duration of the catheter therapy,
and anatomy. Tunneling could be preferred in older patients with obesity or
mobile skin over the neck and when longer duration of catheter infusion is
expected. Two main disadvantages of tunneling are the risk of catheter
dislodgment during the tunneling and the potential for scar formation.
Fortunately, a number of catheter-securing devices are available to help
stabilize the catheter.
NYSORA Highlights
Both stimulating and nonstimulating catheters can be used, although for
simplicity we prefer nonstimulating catheters for     ultrasound-guided
continuous interscalene block.