Nerve block: digital block

Background

Deep palmar nerves

• Each digit is innervated by 4 nerves
  • 2 Dorsal (10 and 2 o'clock positions)
  • 2 Ventral - palmar or plantar (4 and 8 o'clock positions)

Indications

• Need to anesthetize entire digit (finger or toe)
  • Laceration repair
  • Dislocation/fracture reduction
  • Pain control for traumatic injury
  • Paronychia
  • Felon
  • Nail trephination or removal

Contraindications

• Overlying skin infection
• Distortion of landmarks

Equipment Needed

• PPE
• Local anesthetic
• 27-30ga needle
• 5-10 mL Syringe
• Iodine or chlorhexadine prep

Maximum Doses of Anesthetic Agents

Agent	Without Epinephrine	With Epinephrine	Duration	Notes
Lidocaine	5 mg/kg (max 300mg)	7 mg/kg (max 500mg)	30-90 min	1% soln contains 10 mg/ml 2% soln contains 20 mg/ml
Mepivicaine	7 mg/kg	8 mg/kg
Bupivicaine	2.5 mg/kg (max 175mg)	3 mg/kg (max 225mg)	6-8 hr	0.5% soln contains 5 mg/ml May cause cardiac arrest if injected intravascularly Do not buffer with bicarbonate
Ropivacaine	3 mg/kg
Prilocaine	6 mg/kg
Tetracaine	1 mg/kg	1.5 mg/kg	3hrs (10hrs with epi)
Procaine	7 mg/kg	10 mg/kg	30min (90min with epi)

Epinephrine in Digital Block

• Previously, "conventional wisdom" argued that it is unsafe to use epinephrine in digital local anesthesia.
• However, many studies going back more than a decade have shown that using local anesthetic with epinephrine is safe for use in digits.
• A Cochrane Review concurs that no adverse effects have been reported, but notes that the level of evidence is poor and further high quality studies are required.

Procedure

Traditional Technique

Cross sectional anatomy of digit with four nerves (dark circles) shown. Note that palmar nerves are more medial than dorsal nerves. Arrow shows needle trajectory of traditional technique.

• Cleanse skin at proximal, dorsal aspect of the digit to be anesthetized, including web space
• Introduce the needle at the base of the digit near the MCP joint, lateral to the midline of the digit.
• Advance the needle around the bone towards the ventral side of the digit - stop if skin tenting is noted
• Inject ~1mL of anesthetic to block ventral digital nerve
• As needle is withdrawn, inject additional ~1mL of anesthetic to block dorsal digital nerve
• Repeat on opposite side of digit

Transthecal Technique

Described for finger blocks - most effective in 2nd-5th digits
Contraindicated if flexor tendon involvement or infection (e.g. felon, tenosynovitis, etc)

• With hand supinated, locate flexor tendon of finger to be anesthetized
• Cleanse skin over the distal palmar crease and proximal digital crease

• Method 1
  • Insert needle 90 degrees to the skin at the proximal digital crease
  • Advance until needle hits bone, then withdraw 2-3mm
  • Redirect needle 45 degrees to the skin with needle pointing distally (towards finger tip)
  • Slowly inject anesthetic - initially no resistance, progressive resistance felt as tendon sheath fills (~1.5-3mL)
• Method 2
  • Insert needle at 45 degrees to the skin just distal to the distal palmar crease
  • Advance into flexor tendon sheath
  • Slowly inject anesthesic - if resistance to injection felt, withdraw needle slightly

Complications

• Damage to surrounding structures
• Bleeding
• Infection
• Accidental intravascular injection of anesthetic

See Also

• Nerve Blocks (Main)

External Links

Videos

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