Median Nerve Block

Aka: Median Nerve Block, Regional Anesthesia of the Median Nerve, Median Nerve Block at Wrist, Forearm Median Nerve Block

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II. Indications

  1. Anesthesia of Median Nerve distribution distal to wrist
    1. Forearm and Wrist Nerve Blocks are primarily sensory (while proximal blocks are also motor)
  2. Consider in combination with Ulnar Nerve Block at Wrist and Radial Nerve Block at Wrist for Complete Hand Anesthesia
    1. See Complete Hand Anesthesia

III. Contraindications (Relative)

  1. Carpal Tunnel Syndrome

IV. Precautions

  1. Avoid Median Nerve
  2. Injection is harmful if improperly done

V. Anatomy: Relationships

  1. Flexor carpi radialis (radial side)
  2. Median Nerve
  3. Palmaris Longus (Ulnar side)
    1. Forms palmar aponeurosis at midline of wrist
    2. Opose thumb and 5th finger to find palmaris longus

VI. Preparation

  1. Needle: 23 to 27 gauge 1.5 inch
  2. Skin Preparation (e.g. Hibiclens or Betadine)
    1. See Regional Anesthesia
  3. Anesthetic
    1. See Regional Anesthesia for Anesthetic options
    2. Local Anesthetic 2-5 ml (Ultrasound) or 5-10 ml (landmark)

VII. Technique: Forearm (Ultrasound, preferred location compared with wrist)

  1. Images
    1. forearmMedianUlnarNerveBlock.jpg
  2. Ultrasound-Guidance
    1. High frequency linear probe in short axis
    2. Use standard Ultrasound-guided Regional Anesthesia technique
    3. Linear probe is transverse to mid-Forearm
    4. Median Nerve, Ulnar artery and Ulnar Nerve lie in a plane between the superficial and deep flexors
      1. Ultrasound at wrist can easily identify ulnar artery and Ulnar Nerve
      2. Slide probe up Forearm, proximally, until Ulnar Nerve and ulnar artery separate
      3. Slide probe medially until Median Nerve is seen in the same plane as the Ulnar Nerve
  3. Needle Insertion
    1. Both Ulnar Nerve and Median Nerve can be blocked in same Ultrasound view, with needle redirection
    2. Approaching from ulnar aspect, rounded Forearm edge allows needle to be perpendicular to probe
    3. May also approach the Median Nerve from the lateral or radial aspect

VIII. Technique: Wrist

  1. Images
    1. medianNerveBlockWristLandmark.jpg
    2. medianNerveBlockWristUltrasound.jpg
  2. Wrist position
    1. Forearm supinated
    2. Dorsiflex wrist to 30 degrees resting on towel roll
  3. Ultrasound-Guidance (preferred)
    1. High frequency linear probe in short axis
    2. Start with probe over mid-Forearm
    3. Median Nerve is "starry night" ovoid structure between flexor digitorum superficialis and profundus
      1. Slide Ultrasound probe distally until a vessel is not adjacent to nerve
      2. Ultrasound-guided injection site will be proximal to landmark-guided injection
    4. Use standard Ultrasound-guided Regional Anesthesia technique
  4. Landmark Injection site
    1. Proximal wrist crease AND
    2. Radial side of following landmark
      1. Wrist midline (1 cm medial to flexor carpi radialis tendon) IF palmaris longus absent OR
      2. Palmaris longus tendon
        1. Find by opposing thumb with pinky or
        2. Flex middle finger against resistance
  5. Needle insertion
    1. Apply antiseptic to skin (e.g. Betadine)
    2. Aim 45 degrees distally toward middle and ring fingers
      1. Some guidelines recommend directing needle proximally at 45 degrees
    3. Insert needle 1-2 cm until no resistance
    4. Do not inject if Paresthesias (see below)
  6. Warning: Distal Paresthesias with needle with injection
    1. Indicates needle is at Median Nerve
    2. Do not inject here!
    3. Remove needle and replace further to the ulnar side

IX. References

  1. Grant and Auyong (2017) Ultrasound Guided Regional Anesthesia, Oxford University Press, New York, 94-103
  2. Eicken and Rempell (2016) Crit Dec Emerg Med 30(4):3-11
  3. Pfenninger (1994) Procedures, Mosby, p. 1036-54
  4. Salam (2004) Am Fam Physician 69(4):896 [PubMed]
  5. Yurgil (2020) Am Fam Physician 101(11):654-64 [PubMed]

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