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The wrist block is a technique for blocking branches of the ulnar,
medial, and radial nerves at the level of the wrist. The wrist block is a
basic peripheral nerve block technique that involves anesthesia of the
median, ulnar, and radial nerves, as well as the dorsal sensory branch of
the ulnar nerve. The wrist block is simple to perform, essentially devoid of
systemic complications, and highly effective for a variety of procedures on
the hand and fingers. As such, skill in performing a wrist block should be
in the armamentarium of every anesthesiologist. Wrist blocks can be used in
the outpatient setting and office setting along with the standard operating
room setting, resulting in safe, effective, and cost-effective anesthesia
that is well accepted by both surgeons and patients.1–8
Wrist blocks are also useful in the emergency setting to provide anesthesia
for repair of hand injuries in the emergency room because there is adequate
anesthesia of the hand without motor blockade of the extrinsic hand
muscles.9
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A wrist block is most commonly used for carpal tunnel and hand and
finger surgery.10,11 The most common hand surgery in the
United States is carpal tunnel release. Paget described carpal tunnel
syndrome in 1853.1,12 Although Learmonth reported release
of the carpal tunnel at the wrist in 1933, it was not until the 1950s that
the surgery became popular through the efforts of Phalen.13–15
Because of the ease of performing a wrist block, wrist blocks
are used in a variety of settings including the emergency room, outpatient
surgery centers, and office-based anesthesia practices. Hand surgeons also
make use of the wrist block to perform minor procedures in their offices. A
wrist block can be used in a patient with a full stomach requiring emergeny
surgery, thereby obviating the need for general anesthesia and reducing the
risk of aspiration.
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The contraindications to wrist blocks are few, but include local
infection at the sites of needle insertion, preexisting central or
peripheral nervous systems disorders, and allergy to local anesthesia.
Patients are usually able to tolerate a tourniquet on the arm without
anesthesia for 20 min; a wrist tourniquet can be tolerated for about 120
min.
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Innervation of the hand is shared by the ulnar, median, and radial
nerves (Figure 29–1). The ulnar nerve innervates more intrinsic
muscles than the median nerve, which in turn innervates digital branches to
the skin of the medial one and a half digits (Figure 29–2). A
corresponding area of the palm is innervated by palmar branches that arise
from the ulnar nerve in the forearm. The deep branch of the ulnar nerve
accompanies the deep palmar arch and supplies innervation to the three
hypothenar muscles, the medial two lumbrical muscles, all the interossei,
and the adductor pollicis. The ulnar nerve also innervates the palmaris
brevis muscle.
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