Radial Nerve Block
Welcome to the Radial Nerve Block regional anesthesia page. Here we will cover indications, contraindications, materials and steps for you to master this procedure. Let’s begin with the overview below.
Overview
Involves local anesthesia of the radial nerve to safely and reliably provide pain relief as well as total loss of feeling if needed for laceration repair, fracture reduction, or other intervention. Wrist blocks are simple to perform, essentially devoid of systemic complications and can be used in an emergency department setting, office, or operating room.
Indications
While most commonly used for finger and hand surgery, wrist blocks can also be used to perform minor procedures or provide acute pain relief.
Contraindications
There are few true contraindications to this block. They include:
- Infection (cellulitis) at the site of injection
- Allergy to local anesthetic being used
- Patient refusal
Some relative contraindications to consider:
- Patient needs a neural exam of the affected extremity
- Anticoagulation use or bleeding disorder (pressure and tourniquet can be applied to the affected area if necessary)
- Patient with prior neural lesion or active injury
Anatomy
The radial nerve passes along the anterior and radial side of the forearm, traveling with the radial artery. Approximately 5 cm above the wrist, it leaves the artery and divides into a superficial and deep branch innervating the skin of the radial/dorsal side of the thumb, as well as the lateral aspect of the dorsal surface of the hand (Figure 1). It is also responsible for the extensor function of the digits.
Materials
Technique
Blocks should be performed with aseptic technique using a skin antiseptic, sterile field, and sterile equipment (i.e. ultrasound) if possible. Allow for appropriate dry time for your antiseptic. Block needles should be aspirated prior to every injection to avoid intravascular administration, and injection should be immediately stopped if the patient suddenly complains of pain or high pressure.
Landmark
- Place the patient’s extremity in a partially pronated position, with the hand resting on the hypothenar area and fifth digit.
- Identify the radial styloid process. Clean and prep the area, then place a skin wheal just dorsal and medial to the radial styloid, at the base of the anatomic snuff box (Figure 2).
- Insert your needle through your skin wheal and inject 5 mL of local anesthetic subcutaneously in this location.
- Infiltrate an additional 5 mL of local anesthetic laterally, toward the radial styloid process.
Note: Given the proximity of the radial nerve to the radial artery and the multiple branches that occur at and around the wrist , landmark-based radial nerve block as described below is not recommended as ultrasound localization and a forearm injection site is preferred.
Ultrasound
- Place the patient’s extremity in the supinated position.
- Using the linear probe, place the US probe on the lateral upper arm. The radial nerve travels in the radial groove of the humerus, then along the lateral aspect in the distal part of the upper arm. Running down the lateral humerus with your probe, you will identify a “honeycomb” hyperechoic structure that moves laterally away from the bone. This is the radial nerve (Figure 3).
- After cleaning the area and placing a skin wheal, approach the radial nerve from the lateral aspect of the forearm to avoid the radial artery (Figure 4). Advance the needle into vicinity of the radial nerve. Aspirate as you go to avoid intravascular administration and use hydro-dissection to verify appropriate location of the needle tip.
- Inject 3-5 mL of local anesthetic in the area around the radial nerve.
Note: Another approach is to move your linear probe up from the wrist crease. The radial artery is easily identified here and the radial nerve will be found in close proximity. As you move up the forearm the nerve will separate from the artery (Figure 5).
Summary & Bullet Points
- Radial nerve block is safe and effective way to provide analgesia/anesthesia to a patient requiring intervention (i.e. laceration repair) in the dermatomal distribution of the radial nerve.
- Very few contraindications exist for this block (overlying infection, medication allergy).
- The radial nerve can be injected blindly at the base of the anatomic snuff box dorsal to the radial styloid process, or via ultrasound in the distal upper arm.