Nerve Block: Median

Background

• Useful for lacerations across multiple fingers/palm instead of multiple digit blocks
• Useful for exploration of flexor tendons of digits 1-3
• Ultrasound guidance significantly increases the success rate of this block

The yellow area indicates the area of the hand innervated by the median nerve

Indications

• Trauma or need to perform painful procedure on area innervated by median nerve

Contraindications

• Infection overlying injection site
• Previous allergic reaction to local anesthesic used
• Distortion of anatomic landmarks

Equipment Needed

• Topical anesthesia (LET, EMLA)
• local anesthesia
  • Lidocaine 1% (lasts 30-60 minutes or longer if given with epinephrine, rapid onset)
  • Mepivacaine 3% (lasts 45-90 minutes, slower onset)
  • Bupivacaine 0.5% (lasts 2-4 hours, slowest in onset)
• 18G needle to draw up anesthetic
• 25-30G needle to inject. Use of a larger gauge (21-23) makes it easier to see the needle on ultrasound
• 10 cc syringe
• Gauze pads

Procedure

Median nerve lies between palmaris longus and flexor carpi radialis.

• Time out, confirm correct patient and laterality
• Apply topical anesthesia if needed
• Draw up 5-10 mL of anesthetic into syringe
  • Beware of toxic dose of anesthetic you're using Local Anesthetic Systemic Toxicity (LAST)
• Before any nerve block, perform neurovascular exam (often includes 2 patient discrimination with paperclip)

Wrist Block

• Median nerve is within the carpal tunnel
• Between palmaris longus and flexor carpi radialis
• Insert needle perpendicular between tendons, 2-3 cm proximal to the distal crease of the wrist
• Aspirate; if no blood inject a few mL's of anesthetic slowly
• Test sensation to pain distal to block

Elbow Block

Upper Extremity Nerves

• Cleanse the skin overlying the antecubital fossa with chosen antiseptic
• Create a sterile field using sterile drape
• In a sterile fashion, apply a small wheel of local anesthetic to the area immediately proximal to the antecubital fossa
• Palpate the brachial artery to be aware of its path
  • The median nerve should be approximately 1 cm medial to the brachial artery at this point
• Insert the needle approximately 1-2 cm proximal to the flexor crease and advance with negative pressure applied to the syringe
• At 1-2 cm deep, aspirate prior to injection to rule out intravascular placement
• Inject 5-10 mL of local anesthetic

Ultrasound Guided Block

• Place a linear probe on the volar aspect of the midforearm
• The median nerve takes the appearnce of a "chocolate chip cookie" in the axial orientation and lies between the flexor digitorum profundus and supeficialis
• Clean and prep the patient's arm under sterile conditions, and insert a 25 g needle in the long axis under ultrasound guidance next to the nerve
• Aspirate to prevent inadvertent intravascular injection
• Inject 5 mL of local anesthetic so that it basks the nerve

Complications

• Bleeding
• Infection
• Pain
• Needle fracture
• Neurapraxia

See Also

• Nerve blocks (main)
• Local anesthetic systemic toxicity

External Links

• Emedicine: Median Wrist Block
• Video: Median and Ulnar Block
• Video: Median Block at Elbow

References

Authors

Daniel Eggeman, Tianjiang Ye, Devin Smith, Jay, Michael O'Brien, MD, Michael Holtz, Ross Donaldson, Neil Young, Daniel Ostermayer