Radial Nerve Block
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Radial nerve block is a simple procedure that can be performed at various levels along the course of the radial nerve. Surgical anesthesia, postoperative analgesia, and palliative measures for acute painful conditions are all indications for radial nerve block.
The radial nerve is 1 of the 4 important branches of the posterior cord of the brachial plexus and has the root values of C5, C6, C7, C8, and T1. The mnemonic STAR (Subscapular, Thoracodorsal, Axillary, Radial) is an easy way to remember the 4 branches.
A brachial plexus schematic, radial nerve sensory distribution, and radial nerve course are shown in the images below.
In the axilla, the radial nerve descends behind the axillary and brachial arteries, passes between the long and medial heads of the triceps muscle, and enters the posterior compartment of the arm. It then winds in the spiral groove of the humerus with the profunda brachii vessels. Just above the elbow, it pierces the lateral intermuscular septum and continues downward into the cubital fossa between the brachialis and brachioradialis muscles. At the level of the elbow (lateral epicondyle), it divides into superficial and deep branches.
Branches of the radial nerve in the axilla
Cutaneous branch – Posterior brachial cutaneous nerve
Muscular branches – Long and medial heads of triceps
Branches of the radial nerve in the spiral groove
Cutaneous branches – Lower lateral brachial cutaneous nerve, posterior antebrachial cutaneous nerve
Muscular branches – Lateral and medial heads of the triceps, anconeus
Branches of the radial nerve in the arm
Articular branch – Elbow joint
Muscular branches – Brachialis, brachioradialis, extensor carpi radialis longus
The superficial branch of the radial nerve descends lateral to the radial artery and passes backward under the tendon of the brachioradialis muscle. It then continues distally between the brachioradialis and supinator muscles before descending onto the dorsum of the hand. [1] It provides cutaneous innervation to the lateral two thirds of the dorsum of the hand and the lateral two and one half proximal phalanxes.
The deep branch of the radial nerve winds around the lateral part of the neck of the radius and enters the posterior compartment of the forearm. It descends between the superficial and deep layers of the supinator muscle and reaches the dorsal aspect of the interosseous membrane. It innervates the extensor carpi radialis brevis, supinator, extensor digitorum, extensor digiti minimi, extensor carpi ulnaris, abductor pollicis longus, extensor pollicis longus, extensor pollicis brevis, and extensor indicis. It also provides articular branches to the wrist and carpal joints.
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Surgical anesthesia along the course of the radial nerve
Supplement to brachial plexus block
Postoperative analgesia
Acute pain emergencies in the course of the radial nerve
Radial tunnel syndrome: [2] This is a painful condition of the radial nerve. To distinguish radial tunnel syndrome from tennis elbow, palpate the lateral epicondyle. In tennis elbow, this palpation reveals tenderness over the lateral epicondyle that is absent in radial tunnel syndrome.
Cheiralgia paresthetica or Wartenberg syndrome: [3] This syndrome is secondary to compression of the radial nerve distal to the musculospiral grove. Compression occurs because of the brachioradialis muscle during forearm pronation. The syndrome is manifested by painful paresthesias and decreased sensation over the dorsum of the hand.
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Patient refusal
Infection at the site
Coagulopathy
Allergy to available local anesthetic
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In adults, the radial nerve block is well tolerated with reassurance from the practitioner. Skin infiltration with lidocaine 1% 0.5-1 mL suffices to facilitate needle entry. For more information, see Local Anesthetic Agents, Infiltrative Administration.
Extremely anxious patients may benefit from oral diazepam 10 mg the night before or intravenous midazolam (1-2 mg, titrated to sedation) prior to the block.
General anesthesia may be needed for pediatric patients.
The choice of the type and concentration of local anesthetic for radial nerve blockade is based on the desired duration. Alkalinization of mepivacaine and lidocaine with sodium bicarbonate results in faster time to onset of anesthesia. Table 1 provides onset times and duration for some commonly used local anesthetics mixtures. [4]
Table 1. Local Anesthetic for Radial Nerve Block (Open Table in a new window)
Local Anesthetic
Onset, min
Anesthesia Duration, h
Analgesia Duration, h
Mepivacaine 1.5%
15-20
2-3
3-5
Lidocaine 2%
10-20
2-5
3-8
Ropivacaine 0.5%
15-30
4-8
5-8
Ropivacaine 0.75%
10-15
5-10
6-24
Bupivacaine 0.5% (or levobupivacaine)
15-30
5-15
6-30
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Alcohol, povidone-iodine solution (Betadine), or chlorhexidine (Hibiclens) preparatory solution
Syringe, 1 mL, for local anesthetic
Syringe, 5 mL, for the block
Needle, 1 in, 25-27 gauge (ga), for the block
Lidocaine 1%, bupivacaine 0.5%, or ropivacaine 0.5%; 5 mL
Depot corticosteroid (eg, methylprednisolone acetate [DepoMedrol] 40 mg, triamcinolone acetonide [Kenalog] 40 mg)
Gauze, 2 X 2
Adhesive bandage
Sterile gloves
All resuscitative equipment
Standard monitoring equipment
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Position the patient comfortably with the affected arm well supported.
Usually, the supine position is preferred, with the arm supported on the side.
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Position the patient supine with the arm abducted 45º and the hand resting comfortably on the abdomen. Radial nerve block land marks are shown in the image below. [2]
Palpate deeply between the heads of the triceps muscle and the brachialis muscle to identify the musculospiral groove.
Prepare the skin with an antiseptic solution.
To facilitate needle entry, infiltrate the injection site with lidocaine 1% 0.5-1 mL.
Insert the 25-ga 1-in needle perpendicularly toward the musculospiral groove.
Identify the nerve by paresthesia or nerve stimulator technique. If no response is elicited, redirect the needle slightly more anteriorly or posteriorly until the response is elicited.
Aspirate gently to identify intravascular location of the needle.
If the aspiration is negative, slowly inject 7-10 mL of the local anesthetic in slow increments, with intermittent aspiration. The image below shows landmarks for a radial nerve block at the humerus level.
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Position the patient as described above.
Identify the lateral margin of the biceps tendon at the elbow crease by flexing the elbow.
Prepare the skin with an antiseptic solution.
Insert the needle just lateral to the tendon and advance it in a slightly medial and cephalad direction toward the humerus. Landmarks for a radial nerve block at the elbow are shown in the image below.
Identify the nerve with paresthesia, nerve stimulation, ultrasonographic guidance, or a combination thereof. [5]
After negative aspiration, slowly inject 7-10 mL of the local anesthetic. Landmarks for a radial nerve block at the elbow are shown below.
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The radial nerve block at the wrist level (landmarks shown below) is essentially a field block and requires a more extensive infiltration because of its less predictable anatomic location and division into multiple, smaller, cutaneous branches. [4, 6]
Inject 5 mL of local anesthetic subcutaneously, just above the radial styloid, aiming medially. Additional landmarks for a radial nerve block at the wrist are shown below.
Extend the infiltration laterally, using an additional 5 mL of local anesthetic.
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The radial nerve block may be performed solely or in combination with ulnar and median nerve blocks.
The radial nerve block may supplement the brachial plexus block. If performing a brachial plexus block at the humeral canal, block the radial nerve before blocking the ulnar nerve. [7]
This block can be performed at the humerus, elbow, and wrist levels.
Lidocaine, bupivacaine, ropivacaine are the local anesthetics typically used for this procedure.
Surface landmarks, paresthesia, nerve stimulation, and ultrasonographic guidance are all helpful in performing the radial nerve block.
Take care to avoid intraneural or intravascular injection of the local anesthetic.
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Complications after wrist block are typically limited to residual paresthesia due to an inadvertent intraneuronal injection. Systemic toxicity is rare because of the distal location of the blockade.
Complications may be avoided by taking preventive measures (see Table 2). [4]
Table 2. Prevention of Complications in Radial Nerve Block* (Open Table in a new window)
Complication
Prevention
Infection
Use aseptic technique
Hematoma
Limit number of insertions (1-2 for superficial block)
Use 25-ga needle to avoid puncturing superficial veins
Vascular puncture
Do not use epinephrine with wrist and finger blocks
Nerve injury
Do not inject when patient reports pain on injection
Do not inject when high pressure is detected on injection
Other injury
Instruct the patient on care of the insensate extremity
*Table adapted from Wrist Block, New York School of Regional Anesthesia
Nishanian E, Gargarian M. Regional anesthesia. Hurford WE, Bailin MT. Clinical anesthesia procedures of the Massachusetts General Hospital. 5th ed. Philadelphia, Pa: Lippincott-Raven; 1998. 264.
Waldman SD. Radial Nerve block at the humerus. Atlas of Interventional Pain Management. 2nd ed. WB Saunders; 2004. Chap 43, pp 166-70.
Overbaugh RH. Peripheral nerve blocks of the upper extremity. Waldman SD. Pain Management. Philadelphia, Pa: Saunders Elsevier; 2007. 2nd ed: Chap 146, p 1233.
Wrist Block. The New York School of Regional Anesthesia. Available at http://www.nysora.com/posts/view/94. Accessed: January 17, 2009.
Wong DM, Gledhill S, Thomas R, Barrington MJ. Sonographic location of the radial nerve confirmed by nerve stimulation during axillary brachial plexus blockade. Reg Anesth Pain Med. 2009 Sep-Oct. 34(5):503-7. [Medline].
Goldstein B. Musculoskeletal upper limb pain. Loeser JD. Bonica’s management of pain. 3rd ed. Philadelphia, Pa: Lippincott-Raven; 2001. 1032.
Guntz E, Herman P, Delbos A, Sosnowski M. The radial nerve should be blocked before the ulnar nerve during a brachial plexus block at the humeral canal. Can J Anaesth. 2004 Apr. 51(4):354-7. [Medline]. [Full Text].
Foxall GL, Hardman JG, Bedforth NM. Three-dimensional, multiplanar, ultrasound-guided, radial nerve block. Reg Anesth Pain Med. 2007 Nov-Dec. 32(6):516-21. [Medline].
Local Anesthetic
Onset, min
Anesthesia Duration, h
Analgesia Duration, h
Mepivacaine 1.5%
15-20
2-3
3-5
Lidocaine 2%
10-20
2-5
3-8
Ropivacaine 0.5%
15-30
4-8
5-8
Ropivacaine 0.75%
10-15
5-10
6-24
Bupivacaine 0.5% (or levobupivacaine)
15-30
5-15
6-30
Complication
Prevention
Infection
Use aseptic technique
Hematoma
Limit number of insertions (1-2 for superficial block)
Use 25-ga needle to avoid puncturing superficial veins
Vascular puncture
Do not use epinephrine with wrist and finger blocks
Nerve injury
Do not inject when patient reports pain on injection
Do not inject when high pressure is detected on injection
Other injury
Instruct the patient on care of the insensate extremity
*Table adapted from Wrist Block, New York School of Regional Anesthesia
Meda Raghavendra (Raghu), MD Associate Professor, Interventional Pain Management, Department of Anesthesiology, Chicago Stritch School of Medicine, Loyola University Medical Center
Meda Raghavendra (Raghu), MD is a member of the following medical societies: American Society of Anesthesiologists, American Society of Regional Anesthesia and Pain Medicine, American Association of Physicians of Indian Origin
Disclosure: Nothing to disclose.
Troy Buck, MD Assistant Professor, Department of Anesthesiology, Loyola University
Troy Buck, MD is a member of the following medical societies: American Society of Anesthesiologists, American Society of Interventional Pain Physicians
Disclosure: Nothing to disclose.
Jasvinder Chawla, MD, MBA Chief of Neurology, Hines Veterans Affairs Hospital; Professor of Neurology, Loyola University Medical Center
Jasvinder Chawla, MD, MBA is a member of the following medical societies: American Academy of Neurology, American Association of Neuromuscular and Electrodiagnostic Medicine, American Clinical Neurophysiology Society, American Medical Association
Disclosure: Nothing to disclose.
Mary L Windle, PharmD Adjunct Associate Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference
Disclosure: Nothing to disclose.
Laurie Scudder, DNP, NP Nurse Planner, Medscape; Senior Clinical Professor of Nursing, George Washington University
Disclosure: Nothing to disclose.
Alex Macario, MD, MBA Professor of Anesthesia, Program Director, Anesthesia Residency, Professor (Courtesy), Department of Health Research and Policy, Stanford University School of Medicine
Alex Macario, MD, MBA is a member of the following medical societies: American Medical Association, American Society of Anesthesiologists, California Medical Association, International Anesthesia Research Society
Disclosure: Received consulting fee for: Merck.
Luis M Lovato, MD Associate Clinical Professor, University of California, Los Angeles, David Geffen School of Medicine; Director of Critical Care, Department of Emergency Medicine, Olive View-UCLA Medical Center
Luis M Lovato, MD is a member of the following medical societies: Alpha Omega Alpha, American College of Emergency Physicians, Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.
Radial Nerve Block
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