Overview of Radial Nerve Block
Radial nerve anesthesia is a procedure which stops signals from being sent in the nerve. This involves using certain medications, known as local anesthetics, which are injected directly where the nerve is located. This effectively “turns off” the nerve for a while, and can then be switched “on” again when needed. This procedure can be carried out wherever nerves are easy to see and reach with an injection.
A radial nerve block specifically helps to numb or provide pain relief to the hand, particularly the back side of your thumb, index and middle fingers, and the outer half of your ring finger. It helps medical practitioners perform procedures on the hands and fingers, ease severe pain in areas related to the radial nerve, diagnose and treat a condition called radial tunnel syndrome (pain in the forearm caused by pressure on the radial nerve), and understand the possible outcomes in cases where the radial nerve has been damaged.
This nerve block can be a good alternative to sedation (use of drugs to make a patient calmer or unconscious for medical procedures). It is particularly helpful for acutely painful conditions such as bone fractures, cuts, and burns as it can offer relief without the need for increasing doses of strong painkillers known as opioids.
Anatomy and Physiology of Radial Nerve Block
The radial nerve is a major nerve in the body that starts from the spinal cord and passes through the arm. This nerve, like a highway, receives input from the levels C5 to T1 of the spinal cord. It lies behind and below a major blood vessel in your arm known as the axillary artery. The radial nerve goes down the arm and to the backside of the upper arm bone (humerus) in proximity to the muscles of the shoulder, arm and forearm, particularly the latissimus dorsi and tricep muscles.
As it travels, the radial nerve splits into smaller branches that help with feeling and movements. Some of these branches include the sensory posterior cutaneous branch that provides feeling to the elbow and back of the forearm, and the superficial and deep branches that manage feeling and muscle motion in the hand. The superficial branch of the nerve handles sensation to part of the thumb, index and middle fingers. The deep branch controls the movement of the forearm-extending muscles.
Knowing the pathway of the radial nerve is essential particularly during a procedure called anesthetic block where anesthesia is applied to numb a specific area. This procedure can be performed in different locations along the nerve’s course such as above the elbow, at the elbow level, or below the elbow. This helps to numb specific areas during surgical or medical procedures.
Why do People Need Radial Nerve Block
A radial nerve block is a procedure performed to numb a portion of your arm or hand in order to offer pain relief or to perform certain medical procedures. This technique might be used for a variety of reasons:
1. If you have multiple cuts in the area that the radial nerve supplies feeling to, you may need a radial nerve block before these cuts can be stitched up.
2. If you’re having surgery on your forearm or hand, including the removal of skin lesions, draining an infection, removing a foreign body, or having a finger amputated.
3. This approach can also be used to relieve pain from injuries and burns.
4. It might be used in cases of hand or finger fractures and dislocations.
5. If other methods of numbing have failed or are not enough, a radial nerve block can be used as rescue pain relief.
6. Sometimes, it’s used alongside another technique, the median nerve block.
7. For conditions such as radial tunnel syndrome, a condition where the radial nerve is pinched when it passes through a tunnel near the elbow.
8. It can also be used to manage persistent pain, such as in lateral epicondylalgia, also known as tennis elbow.
9. You may have a radial nerve block to control pain after certain procedures such as arthrolysis and tenolysis, that free up joints or tendons.
When a Person Should Avoid Radial Nerve Block
A radial nerve block is a procedure that’s not recommended in certain situations:
- If the person does not agree or is not fully informed about the procedure.
- If the injection area on the body has an infection, an abscess (which is a swollen area within body tissue, containing an accumulation of pus), or cellulitis (a common skin infection).
- If the person is allergic to the type of local anesthetic being used.
- If there’s a chance the person could end up with what’s called local anesthetic systemic toxicity. That’s when too much local anesthetic is used, and it gets into the person’s system, posing a health risk.
For more details on how anesthetics work and move through the body, refer to Table 1.
Equipment used for Radial Nerve Block
To perform a nerve block procedure guided by ultrasound on your arm (specifically, the radial nerve), your doctor will need several items:
An ultrasound machine with a high-frequency linear array transducer (10 to 15 MHz) is used. This is simply a device that uses sound waves to create an image, helping the doctor guide the procedure accurately.
A sterile cover for the ultrasound probe, or a protective dressing called Tegaderm, ensures hygiene and reduces the risk of infection.
Sterile ultrasound gel aids in transmitting the images better by reducing air pockets between the probe and the skin.
Your skin will be cleaned before the procedure with a sterile skin preparation, typically 2% chlorhexidine or a similar disinfectant, to prevent infection.
A 22-G to 25-G, 38-mm to 50-mm, short-bevel block needle will be used. This is a slim needle designed to deliver the anesthetic effectively, with its bevel (angled point) designed to make insertion more comfortable.
The doctor will wear sterile gloves to maintain cleanliness during the procedure.
Local anesthetic will be used. This is a medication that numbs a specific area in your body, in this case, your arm. About 3 to 5 ml (a little less than a teaspoon) should be enough. The anesthetic needs to encircle the nerve sheath (sort of like a protective cover around the nerve). The health care provider has to decide on the most suitable anesthetic and its concentration before starting the procedure, balancing its strength against how long it needs to last.
As for the setup, it’s recommended that the doctor stands on the same side of the body as the arm being treated. The ultrasound machine should be on the opposite side. This setup makes it easier for them to perform the procedure.
Who is needed to perform Radial Nerve Block?
The procedure should be done by people who have been trained well and have experience using ultrasound to guide regional anesthesia. They need to have enough support from other medical staff too.
Preparing for Radial Nerve Block
After getting the patient’s permission, the doctor will place the patient in a certain position based on the chosen method for their radial nerve block, which is a type of local anesthesia used to numb a specific area. More details about this method will be provided in the technique section.
Next, the doctor will clean the skin over the area where the anesthetic will be injected using either povidone-iodine or chlorhexidine 2% – these are antiseptic solutions used to kill germs.
After that, a sterile cover is placed over the ultrasound probe, which is a device that uses sound waves to create a picture of the inside of the body, to prevent any infection. A sterile gel is then applied to the site where the injection will be given.
The last step is to draw the local anesthetic into a syringe. This substance will numb the area to prevent feelings of pain during the procedure.
It’s also important that the patient is carefully monitored during this process, and a 20% lipid emulsion is kept ready. This is a special fat-based substance used to quickly reverse the effect of the anesthetic if too much gets into the bloodstream, leading to a rare but serious condition called local anesthetic systemic toxicity which can affect your heart and brain.
How is Radial Nerve Block performed
There are three methods to numb the radial nerve, one of the main nerves in your arm.
Method 1: Upper Third of the Forearm
The radial nerve can be numbed where it joins the side of the main artery of the forearm before it divides into smaller branches.
1. You can either lie down or sit up for this procedure. Turn your palm downwards to make it easier for the doctor to place the needle. The doctor will stand on the side of your arm.
2. At this point, the radial nerve is underneath a muscle called the brachioradialis. The doctor will use an ultrasound to exactly locate the nerve. They will use a thin needle to inject the anesthetic (drug that numbs the area).
3. The ultrasound helps to see the nerve as a bright area under the muscle.
The needle is carefully placed through the muscle towards the nerve from the side. Before injecting the anesthetic, the doctor makes sure that the needle hasn’t entered any blood vessels. The anesthetic is then slowly injected into the area under the muscle around the nerve.
Method 2: The Elbow in the Antecubital Fossa
The radial nerve can also be numbed in the bend of the elbow, before it divides into the branches that handle sensation and movement.
1. You can either lie down or sit up. Turn your arm so that the palm faces upwards. The doctor stands on the side of your arm.
2. Using the ultrasound and a needle, the doctor follows the same steps to locate and numb the nerve.
3. The nerve is located between two muscles in this area.
After finding the nerve, the doctor decides the best place to inject the anesthetic before it divides into branches. The same checks are followed to make sure the needle is not in a blood vessel before injecting the anesthetic.
Method 3: Above the Elbow Just Below the Humeral Spiral Groove
The radial nerve can also be numbed near the spiral groove on the outer side of the upper arm bone where it divides into the sensation and movement branches.
1. For this procedure, you would need to lie down. Your arm would need to be folded and rested on your chest. The doctor stands on the side of your arm.
2. The ultrasound and needle are used to locate and numb the nerve in a similar way as described before.
3. The nerve appears as a bright, triangle shaped area coming off the upper arm bone.
After locating the nerve with the ultrasound, the needle is carefully placed next to the nerve. The doctor makes sure they aren’t in a blood vessel before injecting the anesthetic.
Possible Complications of Radial Nerve Block
There can be several complications after a medical procedure, including:
* Injury to the nerves, which can lead to temporary numbness (neuropraxia) or permanent damage (neurolysis)
* Formation of a hematoma, which is a collection of blood outside of the blood vessels
* Muscle pain, also known as myalgias
* Occurrence of injections into blood vessels
* Toxicity from local anesthesia which can affect the entire body
* Risk of infection
* Bleeding at the site where the needle enters your skin
* Allergic reaction to the numbing medicine used in local anesthesia
* Damage to muscle tissues and cells, which can occur with frequent or long-lasting injections. This is known as myotoxicity and myonecrosis
* Reflex sympathetic dystrophy, a type of chronic pain condition
What Else Should I Know About Radial Nerve Block?
Local peripheral nerve blocks are commonly used to reduce pain during and after surgery, as well as to treat severe and long-term pain conditions. Their use has grown significantly thanks to ultrasound technology.
Ultrasound-guided techniques improve the effectiveness and efficiency of these nerve blocks. They work by giving doctors a clearer view, ensuring the medicines are delivered accurately and reducing the risk of any harm or reactions caused by local anesthetics. These techniques have made the whole process of numbing nerves during the surgery safer and more successful.
