10.11 Digital Block
===================

agk's Library of Common Simple Emergencies

It is necessary to provide complete anesthesia 
when treating most fingertip injuries. Many 
techniques for performing a digital nerve block 
have been described. The following is one that 
is both effective and rapid in onset. This type 
of digital block will only provide anesthesia 
distal to the distal interphalangeal joint, but 
this is most often the site that demands a 
nerve block.

What to do:
-----------

- Cleanse the finger and paint the area with 
    povidone-iodine (Betadine) solution.
- Using a 27 gauge needle, slowly inject 1% 
    lidocaine midway between the dorsal and 
    palmar surfaces of the finger at the 
    midpoint of the middle phalanx.
- Inject straight in along the side of the 
    periosteum. Then pull back without removing 
    the needle from the skin and fan the needle 
    dorsally.
- Advance the needle dorsally and inject again. 
    Pull the needle back a second time and, 
    without removing it from the skin, fan the 
    needle in a palmar direction.
- Advance the needle and inject the lidocaine 
    in the vicinity of the digital 
    neurovascular bundle.
- With each injection, instill enough lidocaine 
    to produce visible soft tissue swelling.
- Repeat this procedure on the opposide side of 
    the finger.
- For anesthesia of the proximal finger as 
    well, a similar block may be performed as 
    far proximally as the middle of the 
    metacarpal. There, the connective tissue is 
    looser, and the needle need not be fanned 
    into digital septae as described above. Be 
    prepared to wait three to ten minutes for 
    adequate anesthesia.
- With painful crush injuries or when the pain 
    will be prolonged, substitute bupivicaine 
    for lidocaine.

What not to do:
---------------

- Do not use lidocaine with epinephrine. The 
    digital arteries are end arteries that can 
    spasm and provide prolonged anesthesia, 
    ischemia of the finger tip, and 
    potentially, necrosis.

Discussion
----------

Digital nerve blocks are often described as 
being injected at the base of the proximal 
phalynx, but it is not necessary to block the 
whole digit when only the distal tip is 
injured, and the first technique above provides 
anesthesia much faster. Toes are difficult to 
separate and it may be easier to perform a 
modified ring block at the base. Over the 
dorsum of the proximal interphalyngeal joint 
the connective tissue is loose enough for 
direct injection of anesthetic, and a digital 
block is not required. Some studies have 
demonstrated digital anesthesia by injecting 2 
mL of buffered lidocaine directly into the 
flexor tendon sheath, using a 25 or 27 gauge 
needle at a 45 degree angle at the distal 
palmar crease.

Illustration
------------

img/cse1011.gif

 ----------------------------------------------------
 from Buttaravoli & Stair: COMMON SIMPLE EMERGENCIES
 Longwood Information LLC 4822 Quebec St NW Wash DC
 1.202.237.0971 fax 1.202.244.8393 electra@clark.net
 ----------------------------------------------------