Digital Nerve Block

Used to provide local anesthesia to the digits for repair, reduction, or drainage

Lacerations

Nail bed injuries

Infections (i.e., felons, paronychias)

Amputations

Fractures or dislocations

CONTRAINDICATIONS

Absolute Contraindications

Transthecal technique contraindicated in cases of infection, including felon, tenosynovitis, and overlying cellulitis

Allergy to lidocaine, bupivacaine, or other selected anesthetic

Relative Contraindications

Complex laceration or other injury involving multiple digits that can be more easily and adequately anesthetized with a nerve block at the wrist

RISKS/CONSENT ISSUES

Pain (site of needle insertion)

Bleeding (local at needle puncture site)

Infection (theoretical risk of iatrogenic infection)

Potential for damage to neurovascular bundle

Paresthesias

Possible need for additional anesthetic or alternate procedures if the initial nerve block fails

General Basic Steps

Aseptic technique

Choose approach and deliver anesthetic

Massage area for 25 to 30 seconds

Test for adequate analgesia

LANDMARKS

The common digital nerves divide into two pairs of nerves corresponding to the dorsal and volar sides of the digits

Palmar Nerve

Located at the 4- and 8 o’clock positions when looking at a cross section of the digit

Supplies the volar surface of the digit and the dorsal surface distal to the distal interphalangeal (DIP) joint for the middle three fingers

Blocking only the palmar nerves will provide adequate anesthesia on fingertip injuries distal to the DIP for the three middle fingers

Digital Nerve

Located at the dorsal 2- and 10 o’clock positions when looking at a cross section of the digit

Supplies the nail beds of the thumb, fifth digit, and dorsal aspects of all three middle fingers up to the DIP

For the thumb and fifth digit, all four nerves must be blocked for fingertip and nail bed anesthesia (FIGURE 52.1)

FIGURE 52.1 Dorsal technique for palmar and dorsal digital nerve block. A: Nerve distribution in hand. B: Traditional digital nerve block. C: Dorsal three-sided ring block. D: Volar three-sided ring block. (Lewis L, Stephan M. Local and regional anesthesia. In: Henretig FM, King C, eds. Textbook of Pediatric Emergency Procedures. Philadelphia, PA: Williams & Wilkins; 1997:481, with permission.)

TECHNIQUE: SEVEN APPROACHES

Patient Preparation

Document neurovascular examination before anesthesia

Place patient’s affected hand/foot comfortably on bedside procedure table with volar surface down (for metacarpal nerve block, traditional ring block, wing block) or volar surface up (for subcutaneous block, transthecal approach or thumb block)

Prepare the digit and web space by using standard aseptic technique

Equipment

Lidocaine or procaine 1% to 2% (or 0.25% bupivacaine for longer, complicated procedures), 2 to 3 mL

An 18-gauge needle for drawing up the anesthetic

A 25- to 30-gauge needle for the nerve block

A 5-mL syringe

Povidone–iodine or chlorhexidine solution

Sterile drapes and sterile gauze

Gloves

Traditional Digital Block (Web-space Block or Metacarpal Nerve Block)

Anesthetizes all digits except great toe

Prepare skin over dorsal surface of web space between metacarpal/metatarsal heads

Aspirate and inject subcutaneous wheal between metacarpal/metatarsal bones on dorsum of hand/foot 1 to 2 cm proximal to web space

Slowly advance needle through the wheal toward lateral volar surface of metacarpal/metatarsal head until slight tenting of the volar surface is appreciated

Aspirate and then inject 2 mL of anesthetic

Repeat the process on the opposite side of the finger/toe

Traditional Three-sided Ring Block

Anesthetizes all digits including the dorsal, medial, and lateral nerve branches of great toe

Give two injections of lidocaine, one on each side of the digit

Locate dorsal–lateral aspect of proximal phalanx at the web space, just distal to metacarpal/phalangeal (MCP) or metatarsal/phalangeal (MTP) joint

Advance needle perpendicular to digit until bone is struck, aspirate and slowly inject 0.5 mL of lidocaine to anesthetize the dorsal nerve

Withdraw needle slightly, then redirect and advance toward volar surface and slowly inject 1 mL of lidocaine

Withdraw needle partially and redirect it medially over dorsal aspect of digit, aspirate and slowly inject lidocaine while withdrawing needle to anesthetize medial and dorsal aspect of digit

Withdraw the needle

Repeat procedure on medial side of digit at site of anesthetized skin

Massage area of infiltrated skin for 15 to 30 seconds to ensure diffusion of the anesthetic

Wait for 5 to 10 minutes to test for efficacy

Four-sided Ring Block

Advantages: Anesthetizes volar side of digits

Disadvantages: May result in ischemic complications

Perform traditional three-sided ring block

Locate anesthetized volar–lateral aspect of proximal phalanx at the web space, just distal to MCP or MTP joint

Advance needle medially, aspirate and slowly inject 0.5 mL of lidocaine to anesthetize the volar side while withdrawing needle

Subcutaneous Block

Prepare skin over volar surface at proximal skin crease

Pinch skin distal to proximal skin crease

Insert needle at midpoint of crease, aspirate and inject subcutaneous 1 to 2 mL wheal

Massage injected area for 15 to 30 seconds to improve diffusion process

Transthecal Approach

Advantages: Single injection and low risk of neurovascular bundle injury

Disadvantage: More painful to inject through volar surface

Anesthetic is infused directly into the flexor tendon sheath at the proximal digital crease on volar surface

Fill 5-mL syringe with lidocaine

Insert 25-gauge needle at a 90-degree angle at the midpoint of the proximal digital crease and advance until bone is struck

Withdraw needle approximately 2 to 3 mm (should be in flexor tendon sheath) and redirect at a 45-degree angle to the long axis of the digit

Aspirate and inject 1.5 to 3 mL lidocaine while palpating tendon sheath with other hand; continue until resistance is felt

After removing the needle, apply pressure over the tendon proximally to facilitate distal spread

Wait for 2 to 3 minutes to test for efficacy of anesthesia

Most effective for middle three fingers (FIGURE 52.2)

Thumb Block

All four digital nerves must be blocked for complete anesthesia of the thumb

Locate the flexor pollicis longus on the volar aspect of the thumb at the level of the proximal thumb flexor crease

The nerves lie immediately adjacent to this tendon

Aspirate and inject 1 to 2 mL of lidocaine along both sides of the tendon (FIGURE 52.3)

Wing Block

Anesthetizes distal digit and nail bed

Prepare the distal digit by using standard aseptic technique

Insert 30-gauge needle perpendicular to the long axis of digit at a 45-degree angle at a point 3 mm proximal to the imaginary intersection of the lateral and proximal nail folds

Aspirate and inject anesthetic across the dorsum of digit parallel to proximal nail fold

Partially withdraw needle and redirect along lateral nail fold

Aspirate and inject anesthetic along the lateral nail fold

Repeat procedure on opposite side of digit if bilateral anesthesia is required (FIGURE 52.4)

FIGURE 52.2 Digital nerve block: Transthecal approach. The needle is directed into the proximal digital crease at a 45-degree angle to the long axis of the digit into the flexor tendon sheath where the lidocaine is deposited slowly.

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