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Regional Anesthesia for the Hand

Authors

Mark J Conroy, MD, FACEP, CAQ-SM
Assistant Professor
Department of Emergency Medicine, Center for Sports Medicine
The Ohio State University Wexner Medical Center

Ryan McGrath, MD
Sergio Alvarez, MD

Summary

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Introduction

  • Regional blocks of the median, radial and/or ulnar nerves are an effective and safe approach to provide anesthesia to the hand
  • Hand blocks can be used for pain control from fractures, burns, blast injuries, and for procedures such as fracture reduction, laceration repair, foreign body removal, and I&D of abscesses. 
  • For analgesia to the the thumb, index, palmar, and/or dorsal side of the hand block the median and radial nerves
  • The median nerve will provide analgesia to most of the palmar surface, thumb, index, and ring finger
  • The ulnar nerve will provide analgesia to the ulnar side of the hand and little finger 
  • One, two, or all three nerves can be blocked to provide analgesia to the desired region(s) of the hand 
  • Use of these regional nerve blocks enables the provider to anesthetize a large and relatively complex surface area while minimizing the volume of anesthetic that may otherwise be required for diffuse application of local anesthetic in these regions. [1]Eren G, Altun E, Pektas Y, Polat Y, Cetingok H, Demir G, Bilgi D, Tekdos Y, Dogan M. To what extent can local anesthetics be reduced for infraclavicular block with ultrasound guidance? Anaesthesist. … Continue reading
  • Studies have shown that performing ultrasound guided anesthetic nerve blocks of the median, radial and ulnar nerves for procedures of the wrist and hand can be performed quickly with little patient discomfort and improve patient satisfaction. [2]Liebmann O, Price D, Mills C, et al. Feasibility of forearm ultrasonography-guided nerve blocks of the radial, ulnar, and median nerves for hand procedures in the emergency department. Ann Emerg Med. … Continue reading
  • They generally do not provide analgesia to the wrist or volar forearm given they do not adequately block the musculocutaneous nerve, medial antebrachial cutaneous nerve, anterior interosseous nerve, or posterior interosseous nerve

Anatomy

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Indications

  • Complex laceration repair
  • Fracture reduction
    • Carpal/Metacarpal fracture reduction
    • Can be used for distal radius fracture, but not always effective
  • Foreign body removal
  • Abscess Incision and Drainage
  • Fingernail removal

Ultrasound Identification of Nerves

  • Blocks can be performed more proximally or distally in the forearm. In general, it is advised to target the location for the nerve block approximately 5-10cm proximal to the wrist crease. The nerves are typically easier to identify due to larger cross-sectional area, as well as having more room to maneuver. In the wrist there are numerous structures packed within a small space such as tendons and arteries. Furthermore, targeting anesthetic blocks of the median, radial and ulnar nerves 5-10cm proximal to the wrist crease ensures that the palmar branches of the Median and Ulnar nerves will also be blocked thus providing more comprehensive anesthesia of the hand and wrist. [3] NYSORA. Ultrasound-Guided Wrist Block – NYSORA. https://www.nysora.com/techniques/upper-extremity/wrist/ ultrasound-guided-wrist-block/.
  • Median Nerve
    • The patient’s forearm should be placed with the volar aspect of the forearm facing upwards (palm up). 
    • The linear ultrasound probe should then be applied in a transverse orientation to approximately the midpoint of the volar forearm.
    • The median nerve should be located as a fibrillar honeycomb-appearing structure between the superficial flexor digitorum superficialis and the deeper flexor digitorum profundus muscles along the fascial plane that separates them. The flexor digitorum profundus can be found lying directly above the interosseous membrane between the radius and ulna. 
    • Alternatively, the median nerve can be identified at the carpal tunnel by placing the ultrasound probe in the center of the volar wrist at the level of the volar wrist crease, and then the probe can be moved proximally. 

Image 1. Median nerve ultrasound identification in the mid-forearm

Image 2. Median nerve ultrasound identification at the level of the carpal tunnel

  • Radial Nerve
    • The patient’s forearm should be placed with the volar aspect of the forearm facing upwards (palm up). 
    • The ultrasound probe should be applied in a transverse orientation over the radial aspect of the volar forearm at approximately the midpoint of the forearm.
    • Identify the bony cortex of the radius (which will appear with distal shadowing) as well as the radial artery which will be located medial to the bony cortex of the radius. 
    • The radial nerve can then be located just lateral (radial) to the radial artery. The radial nerve will appear relatively small compared to the radial artery at this point along the forearm.
    • The radial nerve can then be tracked proximally towards the elbow and will increase in size as it is tracked.

Image 3. Radial nerve ultrasound identification in the mid-forearm

  • Ulnar Nerve
    • The patient’s forearm should be placed with the volar aspect of the forearm facing upwards (palm up). 
    • The ultrasound probe should be applied in a transverse orientation over the ulnar aspect of the volar forearm at approximately the midpoint of the forearm.
    • Identify the ulnar artery in this plane. Color doppler can be utilized to ensure the structure identified is in fact the ulnar artery as it should have a pulsatile flow pattern when color doppler is applied.
    • Identify the ulnar nerve directly medial to the Ulnar Artery.
    • The ulnar nerve can be tracked proximally towards the elbow where you will see the ulnar nerve and ulnar artery begin to separate as the artery dives deeper into the soft tissues of the forearm. 

Image 4. Ultrasound identification of the ulnar nerve in the distal forearm

Image 5. Ultrasound identification of the ulnar nerve in the mid-forearm

Materials

  • Ultrasound with linear probe
  • Sterile field (drapes)
  • Sterile gauze
  • Skin sterilization (chlorhexidine, iodine, etc)
  • Sterile gloves
    • Ideal but not necessary. Gloved hand should not touch the prepared sterile field on the patient.
  • Needles
    • Various sizes indicated based on provider’s preference 
    • 22 gauge 1 ½” needle most commonly utilized 
    • 25 gauge 1 ½” needle also commonly used
  • Syringes
    • 5 – 10 cc (injecting anesthetic)
  • Local anesthetic (See Introduction to Regional Anesthesia for more details)
    • Lidocaine 1% without epinephrine (10mg/ml)
      • 1% Lidocaine without epinephrine is the most readily available and commonly used local anesthetic as it provides a rapid time of onset (1-3 minutes) and suitable duration of effect (30-120 minutes) to complete commonly associated procedures.
    • Lidocaine 1% with epinephrine (10mg/ml)
      • Provides longer duration of action
    • Bupivacaine 0.5% (5mg/ml)
      • Typically 3-5ccs of anesthetic is all that is needed to achieve effective anesthesia. 
      • 0.5% Bupivicaine is also commonly available. If used, it is typically used in place of 1% lidocaine due to its prolonged duration of effect (120-240 minutes) despite having a slower onset of effect (5-10 minutes) 
  • Optional
    • Skin marking pen (optional)
    • Ethyl chloride (optional), 
      • Use of ethyl chloride does not negatively affect the sterile field.

Contraindications

  • Absolute Contraindications
    • Overlying cellulitis or infection
    • Allergy to anesthetic (consider using an ester anesthetic)
    • Suspected or high index of concern for acute compartment syndrome
  • Relative Contraindications
    • Abnormal or altered anatomy
    • Uncooperative patients
    • Pre-existing peripheral neuropathies
    • Injury proximal to block

General Procedure for Performing Hand Nerve Block

  • Obtain informed consent
    • Discuss risks and benefits with patient
      • Risks include infection, iatrogenic nerve injury, arterial puncture & hematoma
    • Set expectations regarding the procedure
  • Perform neurovascular exam and document
  • Place the patient in position with the volar aspect of the forearm facing upwards (palm up position). Additionally position the ultrasound in direct line of sight to the practitioner. 
  • Identify target nerve(s) and location for intended anesthetic block utilizing high frequency linear ultrasound probe and mark location of intended injection using sterile marking pen.
  • If having difficulty identifying the desired nerve, using color doppler to identify the corresponding artery will aid in localizing the nerve which typically runs with or near its corresponding artery.
  • Sterilize skin using (chlorhexidine)
  • Place sterile drapes to establish the sterile field. 
  • Apply sterile ultrasound probe cover and sterile gel to field and re-identify targeted nerve at marked location.
  • Insert needle with in-plane approach under ultrasound guidance and administer 2-5ccs of local anesthetic around perineurium of the targeted nerve to create a “halo” around the nerve.
  • Perform post-procedure neurovascular exam

Pearls and Pitfalls

  • It is critical to identify the accompanying artery and draw back before attempting the desired nerve block in order to avoid arterial puncture. 
  • Avoid direct contact with the nerves by directing anesthetic in the fascial plane around the nerve. Do not inject into the nerve!
  • Performing nerve blocks 5-10cm proximal to the wrist will ensure capture of all nerve branches supplying sensory innervation to the hand and wrist. 
  • Radial nerve block below the elbow will avoid causing wrist drop.
  • Forearm blocks are unable to provide anesthesia for the volar forearm due to innervation by the musculocutaneous and medial antebrachial cutaneous nerves.

References[+]