Your patient is a 25 year old male with a shoulder dislocation.  He needs analgesia, but has a date later and does not want to risk dimming his considerable mental acuity with systemic medications.  What to do?

Consider an ultrasound guided nerve block.

Interscalene plexus block

Nerve roots c5-t1 coalesce into the brachial plexus and eventually form the terminal nerves supplying the upper extremity.  The plexus can be effectively blocked at multiple locations with more proximal blocks necessary to anesthetize the upper arm.  An interscalene block at the level of the cricoid cartilage (at the c6 transverse process) will anesthetize the shoulder and upper arm.  A block at this level often does not include the inferior trunk so some median and ulnar function may be preserved, so do not use if for distal procedures.

finding your target:
use a high frequency linear probe.  with the head turned away from you scan the anterior neck in the transverse plane at the level of the cricoid.  start by identifying the trachea and move laterally noting the sternocleidomastoid and the great vessels (carotid and internal jugular)


Trachea, sternocleidomastoid, carotid, IJ

Continue to move laterally and posterior looking for the anterior scalene muscle.  It will be deep to the lateral border of the SCM and lateral to the great vessels.  the middle scalene muscle is behind this and the plexus is in between the two scalene muscles.

Carotid, anterior scalene, plexus, middle scalene

Be careful:
-aspirate prior to injection, you are right next to the great vessels
-can result in horner’s syndrome (recurrent laryngeal nerve).  avoid in patients with airway concern
-the phrenic nerve lies anterior to the interscalene space.  block is usually well tolerated, but should make you think twice about preforming this procedure in anyone but young healthy patients
-monitor for signs pneumothorax or hematoma



References: adapted from and images linked from:
Bunting, Leonard V. “Interscalene Plexus Block.” Interscalene Plexus Block. Sonoguide, 2008. Web. 27 Aug. 2015.

May 2024