Ultrasound Techniques

Ultrasound-guided Interscalene Brachial Plexus Block - Single Injection

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; 250mg -500mg 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:

    1. Betadine soaked sponges
    2. 4”x4” gauze packs
    3. Sterile gel for the ultrasound probe
    4. Local anesthetic (30-40ml)
    5. Insulated nerve stimulator needle (50 mm)
    6. Injection pressure monitor (optional)
    7. Sterile gloves
    8. Surface electrode (optional)
    9. Nerve stimulator (optional)
    10. Ruler and skin marker
    11. 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

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 (<20 psi). Thirty to forty ml of local anesthetic is more than adequate for reliable blockade of the brachial plexus.

Typical indications for this block are surgery on the shoulder, lateral clavicle, acromioclavicular joint, proximal humerus and elbow (with low interscalene block).

 

 

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DISCLAIMER: The material presented on this Web page has not been peer-reviewed. The indications, techniques and dosages on this Web page have been recommended in the medical literature and/or conform to OUR clinical practice. The medications and equipment have not necessarily been approved by the Food and Drug Administration (FDA) for use in the techniques and dosages for which they are recommended. The package insert for each drug and/or equipment should be consulted for use and dosage as recommended by the FDA. Because standards, practices and recommendations change, it is advisable to keep abreast of revised recommendations, particularly those concerning new drugs and techniques. While the techniques and dosages described are successfully used in our practice, they should be followed with a discretion since their complications may be dependent on the operator, patient and/or other accompanying clinical circumstances. The development and maintenance of this web page has not been supported by any pharmaceutical or medical manufacturing industry. The medications and/or equipment discussed in the web page is shown solely for teaching purposes. Similar equipment or medications from other manufacturers may produce similar clinical results to ours.