Enter the skin at the site of the local skin wheal in a lateral to medial in-plane approach. Flatter needle angles will allow for better needle visualization, which will depend on the depth and location of the brachial plexus. Advance the needle in 1- to 2-cm increments, maintaining clear visualization of the needle tip at all times. This block may be performed with either an in-plane or out-of-plane approach.
Explore This IssueACEP News: Vol 31 – No 02 – February 2012
In many cases, the authors prefer an in-plane approach because the needle tip can be better visualized, allowing for more precise intraplexus injections. The needle is inserted lateral to the lateral aspect of the transducer. For a periplexus injection, the needle tip is advanced through the middle scalene muscle to the lateral border of the deepest nerve root. Local anesthetic (15-20 mL) is delivered into the potential space between the middle scalene muscle and the brachial plexus sheath (Fig. 7).
For an intraplexus injection, the needle is advanced into the brachial plexus sheath between the two most superficial nerve roots and a low-volume injection of 5-10 mL may be used. For all ultrasound-guided nerve blocks, frequent aspiration to confirm lack of vasculature puncture and visualization of the needle (including needle tip) are recommended before injection.
Finally, if anechoic fluid is not seen on the ultrasound screen (or if high injection pressures or parethesias are encountered) when injecting anesthetic, the procedure should be halted, and the visualization of the needle tip should be confirmed. Local anesthetic will track around the brachial plexus bundle, producing the classic “donut” sign.
Evaluating Block Efficacy
Successful blocks are associated with direct visualization of hypoechoic anesthetic adjacent to the brachial plexus in the interscalene groove, as well as fluid tracking in the fascial plane. Waiting at least 20 minutes before performing the motor and sensory exam of the upper extremity is recommended. Block duration should be approximately 1-3 hours, but a block occasionally lasts as long as 6 hours.
After the block is performed, the time and date of the block should be marked on the patient’s skin with a sterile marking pen (if they are being admitted) or noted in discharge paperwork. Patients should be reminded that they are at risk of injuring the affected extremity because of the anesthesia. A sling should be provided to support the arm even if not otherwise warranted by the injury. Patients should be given strict verbal and written instructions to return for persistent paresthesias, weakness, or severe pain that lasts more than 48-72 hours.
The interscalene approach to the brachial plexus block provides effective anesthesia for painful traumatic and infectious conditions of the upper extremity. Ultrasound guidance allows the emergency physician to perform this block safely. The interscalene brachial plexus is identified between the scalene muscles at the level of the larynx, or followed up from the supraclavicular location, where the plexus is more unified. Local anesthetic is delivered via the periplexus or intraplexus approach, with the needle visualized in-plane. The patient’s neurologic exam should be recorded before and after the block, and appropriate aftercare and return precautions given.
- Blaivas M, Adhikari S, Lander L. A prospective comparison of procedural sedation and ultrasound-guided interscalene nerve block for shoulder reduction in the emergency department. Acad. Emerg. Med. 2011;18(9):922-7.
- Stone MB, Wang R, Price DD. Ultrasound-guided supraclavicular brachial plexus nerve block vs procedural sedation for the treatment of upper extremity emergencies. Am. J. Emerg. Med. 2008;26(6):706-10.
- Kapral S, Greher M, Huber G, et al. Ultrasonographic guidance improves the success rate of interscalene brachial plexus blockade. Reg. Anesth. Pain Med. 2008;33(3):253-8.
- Urmey WF, Talts KH, Sharrock NE. One hundred percent incidence of hemidiaphragmatic paresis associated with interscalene brachial plexus anesthesia as diagnosed by ultrasonography. Anesth. Analg. 1991;72(4):498-503.
- Riazi S, Carmichael N, Awad I, Holtby RM, McCartney CJL. Effect of local anaesthetic volume (20 vs 5 ml) on the efficacy and respiratory consequences of ultrasound-guided interscalene brachial plexus block. Br. J. Anaesth. 2008;101(4):549-56.
- Marhofer P, Harrop-Griffiths W, Willschke H, Kirchmair L. Fifteen years of ultrasound guidance in regional anaesthesia, Part 2: Recent developments in block techniques. Br. J. Anaesth. 2010;104(6):673-83.