Anesthesia of the hand

Indications

• Local anesthesia has many practical uses and is straightforward to administer because of the superficial nature and consistent anatomic course of the sensory nerves surrounding the hand and wrist. It is increasingly used as the sole anesthetic in the outpatient setting for WALANT (wide awake, local anesthesia, no tourniquet) procedures.

• Local anesthetics can be administered to individual digits (digital block) along named sensory nerves, such as the superficial radial and dorsal ulnar branches, or locally in random patterned areas to provide complete anesthesia.

• This technique facilitates detailed examinations of important structures within the digits and hand in an emergency room setting, such as ensuring tendon continuity in a patient with an acute digit laceration.

• Local anesthesia is also useful when evaluating a patient’s motion in real time in the operating room. For example, it may be used to ensure that a complete A1 pulley release has been performed with no residual triggering.

• This technique is also useful for patients with critical cardiopulmonary illness because it can obviate the need for general anesthesia.

Clinical examination

Surgical anatomy

• Fig. 1.1 shows the sensory distribution of the dorsal hand.

  

• Fig. 1.2 shows the location of the radial, median, and ulnar nerves. The radial nerve crosses the wrist in the area of the radial styloid. The purely sensory nerve arborizes proximal to the radial styloid and crosses the wrist divided into a few major branches that travel in subcutaneous tissues anywhere from just volar to the styloid and as far dorsal/ulnar as the area in line with the middle finger metacarpal ( Fig. 1.3 ).

  
  

• The median nerve crosses the wrist within the carpal tunnel, and the palmar cutaneous branch crosses in a similar region of the wrist but more superficially. The nerve runs between the palmaris longus (PL) and the flexor carpi radialis (FCR) tendons, and for patients with PL, this tendon can be used to help landmark for injections.

  • To identify the PL, have the patient pinch their thumb to their ring/small finger and locate the tendon bulge in the wrist ( Fig. 1.4 ).

    

  • If not present or identifiable, the ulnar border of the FCR tendon can be used as the landmark.

• The ulnar nerve crosses the wrist in the area of the flexor carpi ulnaris (FCU) tendon, proximal to its insertion on the pisiform (before entering the Guyon canal).

  • The ulnar artery is radial to the nerve and to the FCU tendon.

  • The dorsal sensory branch also runs ulnar to FCU at the level of the wrist, more superficial to the major ulnar nerve trunk ( Fig. 1.5 ).

    

• Common digital nerves travel between the metacarpals. The injection site to perform a block of the common digital nerve to anesthetize multiple fingers at once is at the level of the distal palmar crease, approximately 1 cm proximal to the metacarpophalangeal joint.

• Each finger has a volar and dorsal nerve on the ulnar and radial sides (for a total of four digital nerves). The volar branches are larger, and within the finger are volar to the corresponding digital artery. The volar branches pass from the common digital nerve proximal to each webspace and enter the finger ( Fig. 1.6 ).

  

Positioning

Blocks are most easily performed with the patient supine and the arm extended out on a hand table. The great degree of motion through the shoulder, elbow, and wrist allow for these blocks to be performed in a variety of hand and arm positions.

Radial nerve block