Nerve block: Intrascalene


Left: the red line corresponds to the course of the subclavian artery, while the yellow line represents the brachial plexus and the "X" represents the site of entry of the needle when performing an interscalene block. Right: diagram of the course of the brachial plexus in relation to other important anatomic structures in the right side of the neck.
  • Provides anesthesia to the shoulder and upper arm.[1]
  • Performed by injecting local anesthetic to the nerves of the brachial plexus as it passes through the groove between the anterior and middle scalene muscles, at the level of the cricoid cartilage.



  • Severe lung disease
    • Due to risk of unilateral pneumothorax
  • Overlying infection
  • Allergy to anesthetics
  • Phrenic nerve dysfunction
    • Specifically contralateral phrenic nerve dysfunction, due to the risk of unilateral paralysis

Equipment Needed

  • Ultrasound (linear probe)
  • Syringe with 25g needle
  • 5-10cc local anesthetic


  1. Place the linear probe at the level of the larynx and find the IJ vein and the overlying sternocleidomastoid muscle (SCM)
  2. Slide the probe laterally until the tapering edge of the SCM is visualized
  3. The anterior and middle scalene muscles lie directly below the edge of the SCM, and the brachial plexus is sandwiched in between the muscles
  4. The C5-C7 roots are usually well visualized and resemble a "traffic light" while C8 and T1 roots are variably visualized
  5. Check with color doppler to ensure no blood vessels in the vicinity
  6. Insert the needle in the long axis underneath the probe and inject the local anethetic next the the roots after hydrodissecting the roots with test injections


  • Phrenic nerve paralysis[2]
    • Causing unilateral diaphragmatic paralysis and respiratory distress.
  • Pneumothorax[3]
    • On the side of the nerve block

See Also

External Links




  1. Ullah H. et al. Continuous interscalene brachial plexus block versus parenteral analgesia for postoperative pain relief after major shoulder surgery. Cochrane Database Syst Rev. 2014 CD007080
  2. Borgeat A et al. Acute and nonacute complications associated with interscalene block and shoulder surgery: a prospective study. Anesthesiology. 2001 Oct. 95(4):875-80
  3. Auroy Y. et al. Major complications of regional anesthesia in France: The SOS Regional Anesthesia Hotline Service. Anesthesiology. 2002 Nov. 97(5):1274-80.