What is the recommended procedure for a 2nd digit (index finger) nerve block?

Digital Nerve Block for the Index Finger (2nd Digit)

For index finger procedures requiring anesthesia, a digital nerve block is recommended as the preferred method due to its ability to provide complete anesthesia with minimal tissue distortion, prolonged analgesia, and decreased postoperative discomfort compared to local infiltration.

Anatomy and Preparation

• The index finger is innervated by four digital nerves:
  • Two dorsal digital nerves (radial and ulnar aspects)
  • Two volar digital nerves (radial and ulnar aspects)
• Equipment needed:
  • 1% lidocaine without epinephrine (3-5 mL)
  • 25-27 gauge needle
  • Sterile preparation supplies
  • Optional: longer-acting agent like 0.75% ropivacaine for extended procedures

Technique for Index Finger Block

Traditional Digital Block Method:

1. Position the patient's hand with palm facing down on a flat surface
2. Identify the web space at the base of the index finger
3. Insert a 25-27G needle at the dorsal web space between the index and middle fingers
4. Advance the needle to the volar aspect without penetrating too deeply
5. Aspirate to ensure no intravascular placement
6. Inject 1-2 mL of anesthetic
7. Withdraw needle to just below skin and redirect toward the radial aspect of the index finger
8. Inject 1-2 mL of anesthetic
9. Total volume should not exceed 4-5 mL per digit

Alternative: Transthecal Approach

1. Identify the midpoint between the proximal digital and proximal interphalangeal joint creases on the volar surface
2. Insert needle perpendicular to the skin into the flexor tendon sheath
3. Inject 1-2 mL of anesthetic solution
4. This single-injection technique has shown 97% success rate for fingers 1

Anesthetic Selection

• First choice: 1% lidocaine without epinephrine 2, 3

  • Onset: 1-3 minutes
  • Duration: 1.5-2.5 hours
  • Maximum dose: 4-5 mg/kg (not to exceed 300 mg total)

• For longer procedures (>1.5 hours):

  • Consider 0.75% ropivacaine
  • Onset: 3.5-5.5 minutes
  • Duration: 19-23 hours of postoperative analgesia 4

Important Precautions

1. Never use epinephrine-containing solutions in digits due to risk of ischemia and necrosis 3
2. Use sterile technique to avoid introducing infection
3. Avoid performing blocks through infected or severely burned tissue
4. Monitor distal circulation after the block, especially with circumferential injuries
5. Stay below maximum recommended doses of local anesthetics
6. Be aware of potential for compartment syndrome in traumatic injuries

Assessment of Block Effectiveness

1. Test for complete loss of pinprick sensation on both dorsal and palmar aspects of the digit
2. Allow adequate time for onset (1-3 minutes for lidocaine, 3.5-5.5 minutes for ropivacaine)
3. If block is incomplete after 5 minutes, consider supplementary injection at the site of incomplete anesthesia

Benefits Over Local Infiltration

1. Complete anesthesia of the entire digit
2. Avoids tissue distortion that occurs with local infiltration
3. Reduces total anesthetic volume needed
4. Prolongs anesthesia duration
5. Decreases postoperative discomfort 2, 3

Potential Complications

1. Hematoma formation at injection site
2. Nerve damage (rare)
3. Local anesthetic systemic toxicity (rare with proper dosing)
4. Inadequate anesthesia requiring supplemental block

Thorough testing of block success is essential to prevent the need for additional anesthesia during the procedure 2. For procedures requiring a bloodless field, a properly performed digital block can reduce bleeding during surgery 5.