Interscalene Block

What is interscalene block?

Shoulder surgery is invasive and can cause varying levels of pain during and after surgery. During surgery, also called the intraoperative period, general anesthesia provides most of the pain relief. After surgery, also called the postoperative 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. 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.


The following surgeries are amenable to interscalene block treatment:

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.

How interscalene block works

The interscalene block can be performed with the patient awake or under general anesthesia. The patient is situated on his or her back with the head turned to the nonoperative side. 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. 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.

Are there risks?

Complications may include hematoma, infection, or allergic reaction. Other complications are more specific to the procedure, such as paresthesias (abnormal skin sensations), anesthetic systemic toxicity, diaphragmatic paralysis, hoarseness, Horner’s 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).

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