Digital block

Background

  • 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)

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)

Epinephrinein 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.[1][2][3]
  • 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.[4]

Procedure

Traditional Technique[5][6]

  • Cleanse skin at proximal, dorsal aspect of the digit to be anesthetized, including web space
  • Introduce the needle perpendicular to the skin 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  • As needle is withdrawn, inject additional ~1mL of anesthetic to block dorsal digital nerve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[7]

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)

References

  1. Denkler K. A comprehensive review of epinephrine in the finger: to do or not to do. Plast Reconstr Surg. 2001 Jul;108(1):114-24.
  2. Krunic AL, Wang LC, Soltani K, Weitzul S, Taylor RS. Digital anesthesia with epinephrine: an old myth revisited. J Am Acad Dermatol. 2004 Nov;51(5):755-9.
  3. Chowdhry S, Seidenstricker L, Cooney DS, Hazani R, Wilhelmi BJ. Do not use epinephrine in digital blocks: myth or truth? Part II. A retrospective review of 1111 cases. Plast Reconstr Surg. 2010 Dec;126(6):2031-4
  4. Prabhakar H, Rath S, Kalaivani M, Bhanderi N. Adrenaline with lidocaine for digital nerve blocks. Cochrane Database Syst Rev. 2015 Mar 19;3
  5. Harness NG. Digital block anesthesia. J Hand Surg Am. 2009 Jan;34(1):142-5.
  6. Hill RG Jr, Patterson JW, Parker JC, et al. Comparison of transthecal digital block and traditional digital block for anesthesia of the finger. Ann Emerg Med. 1995 May;25(5):604-7.
  7. Hart RG, Fernandas FA, Kutz JE. Transthecal digital block: an underutilized technique in the ED. Am J Emerg Med. 2005 May;23(3):340-2.