Interscalene Block


Interscalene Block for Shoulder and Arm Surgery

If you have a severe arm or shoulder injury that’s causing you chronic pain and loss of function, you may have to undergo surgery to repair the damaged area. If you undergo any type of arm or shoulder surgery, you will likely receive general anesthesia and a type of regional anesthesia called an interscalene block.
If you’re experiencing chronic pain in any part of your body, doctors at the Pain Relief Center want to give you relief. For more information, give us a call at 214-709-1904.

What is an Interscalene Block?

An interscalene block is a type of regional anesthesia that numbs your arm and shoulder before surgery. Oftentimes, an interscalene block is also used with general anesthesia.

How Does an Interscalene Block Work?

The brachial plexus is a bunch of nerves in between two scalene muscles that controls the movement and function of the shoulder and arm by sending signals from the spinal cord to these areas. Basically, an interscalene block works by numbing the shoulder and arm so they don’t receive any pain signals from the brachial plexus nerves. Patients can expect anywhere from six to 12 hours of pain relief from an interscalene block depending on the dosage given and how quickly the patient metabolizes the anesthetic.

Brachial Plexus Anatomy

The brachial plexus begins near the bottom of the neck and extends to the area where the arm connects to the shoulder (the axilla) and then down the arm. Cervical spinal nerves C5, C6, C7, and C8 form the brachial plexus along with T1, which is the first thoracic spinal nerve. For the sake of understanding and explaining the anatomy of the brachial plexus, it’s divided into five parts: roots, trunks, divisions, cords, and branches.


The roots are basically the spinal nerves that make up the brachial plexus: C5 through T1, which are anterior rami. Basically, each spinal nerve separates into an anterior and a posterior ramus. The anterior ramus sends signals to the skin and muscles in the arms and shoulders while the posterior ramus sends signals to the skin and muscles in the back. As stated previously, the roots of the brachial plexus extend between the two scalene muscles.


The brachial plexus roots form three trunks near the bottom of the neck, they are:
  • Superior trunk: C5 and C6 roots
  • Middle Trunk: C7 root
  • Inferior Trunk: C8 and T1 roots


Each brachial plexus trunk separates into two divisions within the posterior triangle of the neck, which is basically the area of the neck that extends from behind the ear to the clavicle.
  • Anterior division: Moves towards the front of the body
  • Posterior division: Moves towards the back of the body
These two divisions extend down the neck and into the axilla, which is the area where the arm connects to the shoulder. This is where the divisions reconnect into the brachial plexus cords.


The anterior and posterior divisions combine into these three cords once they reach the axilla area:
  • Lateral cord: Formed by the anterior divisions of the superior and middle trunks
  • Posterior cord: Formed by the posterior divisions of the superior, middle, and inferior trunks
  • Medial cord: Formed by the anterior division of the inferior trunk
These three cords then lead into the brachial plexus’ major branches, which is the last part of this bundle of nerves.


Lastly, the brachial plexus is made up of five major branches which are responsible for sending signals to the skin and muscles in the arms.
  • Musculocutaneous nerve: Provides function and feeling to the upper arm muscle that flexes the elbow (brachialis), the biceps, and the muscles that extend from the clavicle to the elbow (coracobrachialis muscles).
  • Axillary nerve: Provides function and feeling to one of the muscles that form the rotator cuff (teres minor) as well as the deltoid muscles.
  • Median nerve: Provides function and feeling to the forearm muscles, the thumb muscles, and two muscles within the index and middle fingers.
  • Radial nerve: Provides function and feeling to the triceps and forearm muscles that are generally wrist and finger extensors.
  • Ulnar nerve: Provides function and feeling to the hand muscles as well as the forearm muscles that flex the wrist and fingers.

How an Anesthesiologist Performs an Interscalene Block

Whenever you receive an interscalene block, you will be awake for the sake of safety. However, you will be lightly sedated to ease and discomfort or anxiety you may feel. You will lay flat on your back with your head turned away from the side of your body that your surgeon will operate on. This head positioning will give the anesthesiologist better access to your neck which is where the brachial plexus nerves are.

Identifying the Brachial Plexus Nerves

Before administering the interscalene block, the anesthesiologist must identify the correct area by tracing your nerves with a marker on your neck.

Nerve Stimulator

Once the anesthesiologists identifies the brachial plexus nerves, they will attach a tiny needle to a handheld nerve stimulator in order to administer the numbing drug. They will clean your skin and then insert the needle. Once the needle approaches the brachial plexus nerves, the nerve stimulator will cause the muscles in the arm and shoulder to twitch. This twitching shows the anesthesiologist that they are in the right position. Lastly, the anesthesiologist will administer the interscalene block through the needle until the twitching stops.


Sometimes, anesthesiologists will use an ultrasound to guide the needle into the right position. If this happens, you will feel some gel and then a transducer moving on your skin.

Benefits of Interscalene Block

An interscalene block has numerous benefits as a regional anesthetic, including:
  • Reduced risk of post-operative nausea as anesthesia wears off
  • Ability to eat and drink sooner after surgery due to lack of nausea
  • Quicker recovery from anesthesia
  • Possibility of going home earlier due to quicker recovery time from anesthesia
  • Lower pain levels after surgery

What Surgeries Require an Interscalene Block?

Any surgery involving the shoulders or arms will generally require an interscalene block. The most common types of surgeries in this area of the body include:
  • Tendon repair
  • Elbow fracture repair
  • Total elbow replacement
  • Acromioplasty, which is a surgery that shaves away part of the shoulder bone in order to relieve friction and pain on the rotator cuff
  • Shoulder fracture repair
  • Total shoulder replacement
  • Shoulder instability or dislocation repair
  • Any type of arthroscopy in the arm, which are generally performed to diagnose and treat joint problems

Side Effects of an Interscalene Block

An interscalene block comes with a few side effects. However, most side effects go away once the anesthetic wears off. Patients undergoing this type of regional anesthetic may experience:
  • Shortness of breath: Sometimes, the interscalene block can numb part of the diaphragm. As a result, patients may experience shortness of breath. It’s important to note that patients will still be able to breathe, they just may not be able to take a full deep breath like they normally would.
  • Blurred vision: Sometimes the interscalene block can numb surrounding nerves that send signals to the face. If that happens, patients may experience blurred vision, droopy eyelids, and pupil size changes on the same side of the body that’s enduring surgery.
  • Hoarse or raspy voice: Additionally, the interscalene block can numb some surrounding nerves that assist voice box functioning. As a result, patients may experience a hoarse or raspy voice.
  • Difficulty swallowing: As stated previously, some surrounding nerves that supply the voice box can be numbed from this anesthetic. Another side effect of this is that patients can wake up feeling like they have a lump in their throat, therefore making it difficult to swallow food or water. Until the anesthesia fully wears off, patients can deal with this through conscious swallowing, or forcing themselves to swallow food and water.
  • Numbness or tingling: As the interscalene block wears off after surgery, patients may experience some minor tingling in their shoulder or arm. If this issue doesn’t completely disappear within one or two days, it’s important to contact your surgeon.

Possible Complications of an Interscalene Block

The interscalene block is generally very safe. But similarly to any other drug or procedure, use of this anesthesia comes with possible complications including:
  • Infection
  • Excess bleeding
  • Punctured carotid artery, which is an artery in the neck that carries blood from the heart to the brain
  • Local anesthetic toxicity
  • Permanent nerve damage
  • Horner syndrome, a rare condition where a nerve pathway from the brain to the face and the eyes is disrupted
  • Allergic reaction
  • Pneumothorax, also known as a collapsed lung
  • Severe low blood pressure
  • Slow heartbeat, also known as bradycardia
  • Permanent brain damage

Who Shouldn’t Have an Interscalene Block?

An interscalene block is not recommended for patients who:
  • Are allergic to numbing medications
  • Have active infections
  • Are using blood thinners
  • Are pregnant
Additionally, if you have a history of chronic lung conditions, breathing difficulties, COPD, or emphysema, you should ask your surgeon if an interscalene block would be appropriate for you. Patients with breathing difficulties could react negatively with this anesthesia because of the shortness of breath and pneumothorax side effects.

Call the Pain Relief Center Today

If you’re experiencing chronic shoulder or arm pain, there are surgical and non-surgical treatment options available. To schedule an appointment with one of our pain management doctors, call 214-709-1904 or fill out our contact form.
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