What Is an Interscalene Block?

Pain-Doctor-Interscalene-Nerve-Block-Injection-Procedure-1Shoulder surgery is invasive and can cause varying levels of pain during and after surgery. During surgery, also called the intra-operative period, general anesthesia provides most of the pain relief. After surgery, also called the post-operative period, nerve blocks can be used for pain relief with regard to general and rehabilitation purposes.

In an interscalene block, a painkiller is injected within the area near the brachial plexus. The brachial plexus is a system of nerves responsible for the sensation and motion in the shoulder, upper arm, forearm, and hand. The brachial plexus courses between the anterior and medial scalene muscles. An interscalene block will temporarily disable the upper extremity with regard to sensation and movement. As a result, interscalene blocks can provide pain relief during or after surgery on the shoulder, clavicle, upper arm, or elbow. The block is not appropriate for forearm or hand surgery due to the inconsistent nature of pain relief with this procedure.

How Is an Interscalene Block Performed?

Pain-Doctor-Interscalene-Nerve-Block-Injection-Procedure-4 copyThe interscalene block can be performed with the patient awake or under general anesthesia. Small doses of sedative can be given before, during, and after the block to help keep the patient calm and maintain a normal blood pressure and pulse. Indications for an interscalene block include shoulder surgery (total shoulder replacement, acromioplasty, rotator cuff repair, and hemiarthroplasty), humerus fracture, and any other arm surgery not involving the medial aspect of the hand or forearm.

The patient is situated on their back with the head turned to the non-operative side. The landmarks to identify include the cricoid cartilage (at the level of cervical vertebra #6), the lateral border of the sternocleidomastoid muscle, and the interscalene groove between the anterior and middle scalene muscles. Some professionals use nerve stimulation or different imaging techniques to better delineate the target of injection.

The approach for the procedure can be anterior or posterior. The area of the neck is well-cleansed and injected. Most adults require 30 to 40 mL of anesthetic injected into the area for the desired result. Care should be taken to avoid the external jugular vein, which often crosses the border of the sternocleidomastoid muscle, and the apex of the lung. The injection should block the shoulder muscles, including the deltoid, infraspinatus, supraspinatus, and teres major. The block generally lasts less than a day.

Generally, interscalene blocks are very safe. Complications may include hematoma, infection, or allergic reaction. Other complications are more specific to the procedure, such as parasthesias (abnormal skin sensations), anesthetic systemic toxicity, diaphragmatic paralysis, hoarseness, Horner syndrome, and pneumothorax (collection of air in the chest causing the collapse of a lung). Horner syndrome consists of miosis (contraction of pupil), ptosis (drooping upper eyelid), and anhidrosis (absence of sweating).

Conditions Related to Interscalene Blocks

The following surgeries are amenable to interscalene block treatment:

  • Humerus fracture
  • Acromioplasty
  • Rotator cuff repair
  • Total shoulder replacement
  • Hemiarthroplasty
  • Any other arm surgery involving the lateral aspect of the forearm or hand

The aforementioned surgeries are associated with significant amounts of pain. An interscalene block can provide analgesia, or pain relief, during and after surgery involving the upper extremity. It is also particularly helpful with the rehabilitation process, providing pain relief in the upper extremity for the needed range of motion and strength.


The procedure of interscalene block was first performed and popularized by Alon Winnie, MD in 1970. An interscalene block involves injecting anesthesia in the area of the brachial plexus, which supplies sensation and motion for the upper extremity. Interscalene blocks are frequently used for pain relief during and after upper extremity surgery. The blocks are well-tolerated, but do have side effects or complications. The effects of the block generally last less than 24 hours. Lastly, interscalene blocks can be an element of the multidisciplinary approach to rehabilitation of the upper extremity after surgery.

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