Interscalene brachial plexus block

Last revised by Andrew Murphy on 23 Mar 2023

An interscalene brachial plexus block is indicated for procedures involving the shoulder and upper arm.

Ultrasound-guided brachial plexus nerve blocks entered the literature in 1989, when Ting et al. detailed their success with axillary nerve blocks in 10 patients 3.

  • reduction of proximal humerus fracture
  • reduction of glenohumeral dislocation
  • frozen shoulder manipulation
  • deltoid abscess aspiration 5
  • local infection
  • severe coagulopathy
  • local anesthetic allergy
  • patient refusal

Full neurovascular exam should be performed and documented, and consent should be obtained 5. A short-acting benzodiazepine or opioid may be used to reduce patient anxiety.

IV access should be obtained, and the patient should be placed on a cardiac monitor. The ultrasound machine should be optimally positioned for ergonomic visualization during the procedure, typically on the opposite side of the bed 1. The patient is positioned supine with their head rotated 45 degrees to the contralateral side. 

  • two 20 mL syringes
  • 20-gauge 3.5-inch blunt-tip block needles
  • 18 and 30-gauge needles
  • IV extension tubing
  • two 10 mL normal saline flushes
  • transparent dressing
  • alcohol swabs, chlorhexidine
  • body marking pen

The relevant anatomy is first defined with a high frequency linear probe, placed in a transverse orientation along the course of the anterior and middle scalenes, roughly around the level of the C6 vertebral body. The internal jugular vein and common carotid may be used as sonographic landmarks.

The transducer should be moved laterally, to the edge of the sternocleidomastoid. The sternocleidomastoid's clavicular head may be identified superficially, as well as the deeper anterior and middle scalenes. Three hypoechoic structures may then be visualized in the interscalene groove, representing the C5-C7 roots. 

Place a skin wheal at site of insertion with 30-gauge needle. Using an in-plane technique with the probe marker directed toward patient midline, the needle is inserted parallel to the ultrasound beam.  The needle is advanced through the middle scalene muscle under real-time guidance until just short of the interscalene groove. The needle is then advanced into the groove with hydrodissection, and circumferential spread of local anesthetic should be achieved, requiring roughly 10-20 mL of lidocaine (higher volume block).

Repeat neurovascular exam should be immediately performed. Type of block, anesthetic, and time procedure was performed should be enumerated in the medical record. Limb should be immobilized and patient educated on follow-up precautions. 

  • hematoma 2
  • hemidiaphragmatic paresis
  • Horner syndrome
  • recurrent laryngeal nerve involvement
  • vertebral artery injection
  • epidural injection
  • pneumothorax
  • sensorimotor function in the proximal upper arm and shoulder affected more profoundly than distal upper extremity
  • C8 and T1 dermatomes often retain sensation


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