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

US Guided- Interscalene Brachial Plexus Block
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Vijay Patel on 15/03/2009 15:51:00

Typical indications for the Ultrasound-Guided Interscalene Brachial Plexus block
are surgery on the shoulder, lateral clavicle, acromioclavicular joint, proximal
humerus and elbow (with low interscalene block).

VIDEO
FIGURE 1
The patient is in semi-sitting supine position with the head  facing away from
the side to be anesthetized. The premedication of an adult,  average size
patient typically consists of 2-4 mg of midazolam; 250mcg  -500mcg  of
alfentanyl administered just before insertion of the needle
TIP: Visualization of the brachial plexus in the interscalene grove can be 
challenging in patients who are tense, moving or exhibit guarding. Proper 
sedation can go a long way toward obtaining quality images.
FIGURE 2
Equipment:
Ultrasound  machine with 8-12 MHz probe
Nerve block  tray with following equipment items:
*Betadine  soaked sponges 	*4”x4”  gauze packs 	*Sterile  gel for the
ultrasound probe 	*Local anesthetic (30-40ml)
* Insulated nerve stimulator needle (50 mm)
* Injection pressure monitor (optional) 	*Sterile gloves 	*Surface electrode
(optional) 	*Nerve stimulator (optional) 	*Ruler  and skin marker  	*Remote 
controller (foot pedal) for the nerve stimulator (optional)
FIGURE 3
Be certain to understand which part of the probe corresponds  to medial,
lateral, superior and inferior part of the screen. After applying a  large,
sterile “Tegaderm” and sterile gel to the probe, touch the end of the  probe
with the finger and observe the position of the shadow that occurs with  the
touch.
TIP: Make  sure that there is no air trapping between the “Tegaderm” and
the probe. Any  trapped air will results in “shadowing” due to the poor
acoustic impedance of  the air.
FIGURES 4-5
Figure 4
Figure 5
The ultrasound probe (10-12MHz) is applied in the axial  oblique plane (Figure
4) closer to the midline and angled to first  visualize the carotid artery
(Figure 5).
FIGURE 6
Note the position of the internal jugular vein (IJ) as the  pressure on the
ultrasound probe is lightened. The internal jugular vein is  positioned slightly
superficially and lateral to the carotid artery. Changing  the pressure on the
probe causes the IJ to open and close.
FIGURE 7
The ultrasound probe is then moved slightly laterally to  visualize the
brachial plexus in the interscalene grove between anterior and  middle scalene
muscles. The roots/trunks (N) of the brachial plexus are  seen stacked between
the scalene muscles usually as round, hypoechoic  structures  (Figure 7).
FIGURE 8
Sliding or angling the ultrasound probe slightly more  inferior allows
visualization in the low-interscalene position in which the  brachial plexus is
positioned in proximity to the subclavian artery.
FIGURE 9
After the brachial plexus is identified on the image, a 50  mm (max)
stimulating needle is inserted perpendicular to the long axis of the  ultrasound
probe. The needle is inserted at the point on the probe that  corresponds to the
location of the brachial plexus on the screen (i.e., if the  brachial plexus
appears on the middle of the screen – the probe is inserted in  the middle of
the probe). The needle insertion results in shadowing of the  ultrasound image
which indicates the path of the needle (Figure 10).
TIP: Make sure to estimate the exact  depth of the brachial plexus (typically
0.5-1.5 cm) before inserting the  needle. The needle should never be inserted
deeper than the depth indicated on  the ultrasound image.
FIGURE 10
As the needle is being inserted into the interscalene  groove, shadowing (blue
arrows) is seen on the ultrasound image. The location  of the shadow should be
in line with the position of the brachial plexus.
TIP: The  needle is best connected to a nerve stimulator (0.8 mA). Appearance
of the  motor response of the brachial plexus serves as additional (but not
essential)  confirmation of the needle placement in the interscalene groove.
FIGURE 11
Injection of local anesthetic is made with monitoring of the dispersion of the
injectate. If the injectate does not appear to fill the lower compartment of the
interscalene space, the needle is slightly advanced (0.5-1cm) and additional
injection is made at a slightly greater depth (0.5-1cm deeper). Local anesthetic
is injected slowly and with frequent aspirations, while avoiding excessive
injection pressures (