Overview

The following three nerves are involved in a wrist block: radial, median, and ulnar.

• 1.
  

  The ulnar nerve has a dorsal sensory branch that arises 5 cm proximal to the wrist crease.

  
  
• 2.
  

  Two techniques can be used to block the ulnar nerve.

  
  
  
  
  • a.
    

    Proximal block:

    
    
    
    
    • (1)
      

      A proximal block anesthetizes the ulnar nerve approximately 6 cm proximal to the wrist crease.

      
      
    • (2)
      

      In most cases, a proximal block will block both branches.

      
      
    • (3)
      

      Variable anatomy is always a risk.

    
    
    
    
  • b.
    

    Distal block:

    
    
    
    
    • (1)
      

      The ulnar nerve is anesthetized near the wrist crease, and the injection of an anesthetic is directed both volarly to anesthetize the ulnar nerve and dorsally to anesthetize the dorsal cutaneous branch.

      
      
    • (2)
      

      The distal block technique ensures that both branches are consistently blocked.

      
      
    • (3)
      

      A distal block is the favored technique.

    
    

  
  

Indications for Use

• 1.
  

  A complete wrist block can be used when soft tissue procedures that cross dermatomal boundaries are performed.

  
  
• 2.
  

  Selective nerve blocks:

  
  
  
  
  • a.
    

    Ulnar: Reduction of fractures about the small finger (particularly boxer’s fractures) and ulnar-sided soft tissue concerns.

    
    
  • b.
    

    Median: Fingertip injuries to the index and long fingers.

    
    
  • c.
    

    Radial: Reduction of fractures about the thumb and dorsal hand soft tissue concerns.

  
  

Precautions

• 1.
  

  An intravascular injection is of particular concern when injecting an anesthetic around the wrist.

  
  
• 2.
  

  Use of epinephrine should be avoided in wrist blocks.

Pearls

• 1.
  

  Asking the patient to make a fist can aid in palpation of anatomic landmarks.

  
  
• 2.
  

  When injecting an anesthetic near the ulnar nerve, look for a fullness in the area radial to the flexor carpi ulnaris (FCU) tendon to confirm correct placement.

Equipment

• 1.
  

  Antiseptic: A chlorhexidine prep stick or alcohol-soaked gauze

  
  
• 2.
  

  Syringe: Three 10-mL syringes

  
  
• 3.
  

  Needles:

  
  
  
  
  • a.
    

    Large-bore, blunt-tipped drawing-up needles

    
    
  • b.
    

    A 1-in., 25-gauge needle

  
  
  
  
• 4.
  

  Anesthetics (for a typical adult):

  
  
  
  
  • a.
    

    Lidocaine: 15 mL of 1%

    
    
  • b.
    

    Bupivacaine: 15 mL of 0.5%

    
    
    
    
    • (1)
      

      Ulnar nerve: 8–10 mL of the anesthetic

      
      
    • (2)
      

      Median nerve: 3–5 mL of the anesthetic

      
      
    • (3)
      

      Radial nerve: 5–8 mL of the anesthetic

    
    

  
  
  
  
• 5.
  

  Sterile gloves

  
  
• 6.
  

  4 × 4 in. gauze

Basic Technique

• 1.
  

  Patient positioning:

  
  
  
  
  • a.
    

    The patient should be seated, and a bedside table should be available to position the extremity.

    
    
  • b.
    

    For median and ulnar nerve blocks, lay the extremity on a bedside table with the elbow extended and the hand supinated.

    
    
  • c.
    

    For radial nerve blocks, lay the extremity on a bedside table with the elbow extended and the hand pronated.

  
  
  
  
• 2.
  

  Landmarks:

  
  
  
  
  • a.
    

    Ulnar nerve:

    
    
    
    
    • (1)
      

      FCU tendon.

      
      
    • (2)
      

      Ulnar styloid.

      
      
    • (3)
      

      Injection of the ulnar nerve is carried out 0.5 cm proximal to the ulnar styloid under the FCU tendon.

    
    
    
    
  • b.
    

    Median nerve:

    
    
    
    
    • (1)
      

      Palmaris longus tendon.

      
      
    • (2)
      

      Flexor carpi radialis (FCR) tendon.

      
      
      
      
      • (a)
        

        The palmaris longus tendon is the more prominent and more medial tendon.

        
        
      • (b)
        

        Be aware that the palmaris longus is absent in about 10%–20% of patients. If only one tendon can be palpated, then it is the FCR tendon.

      
      
      
      
    • (3)
      

      Wrist crease.

      
      
    • (4)
      

      Injection of the median nerve is carried out 2 cm proximal to the wrist crease between the FCR and palmaris longus tendons.

    
    
    
    
  • c.
    

    Radial nerve:

    
    
    
    
    • (1)
      

      Radial styloid.

    
    

  
  
  
  
• 3.
  

  Steps:

  
  
  
  
  • a.
    

    Block the ulnar nerve.

    
    
  • b.
    

    Block the median nerve.

    
    
  • c.
    

    Block the radial and lateral antebrachial cutaneous nerves.

  
  

Detailed Technique

Prepare the anesthetic; three 10-mL syringes should be prepared.