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The interruption, interference, or blockade of painful stimuli
has been used in the management of pain for several decades. Acute,
chronic, and postoperative pain can be diminished with various types
of regional anesthesia or specific nerve blocks. In the setting
of chronic pain management, various peripheral nerve blocks can
be diagnostic, prognostic, or therapeutic in nature. A nerve block
involves the injection or infusion of a short- or long-acting local
anesthetic around a peripheral sensory nerve, motor nerve, or sympathetic
nerve plexus. In addition to local anesthetic, a steroid preparation
may be added to decrease any suspected inflammatory process. Neurolytic
nerve blocks can be performed utilizing various techniques including
chemical, heat, or cold. Chemical agents such as alcohol or phenol
are used for the selective destruction of nerves. Pulsed radiofrequency
and cryoanalgesia cause neurolysis via heat or cold lesioning. Advances
in fluoroscopic imaging and computed tomography (CT) scanning allow
direct visualization and targeting of specific nerves and nerve
plexuses. Other improvements include the use of nerve stimulators
during interscalene and axillary blocks or sensory and motor nerve
stimulation performed during radiofrequency procedures to assist
in accurate needle placement.
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Nerve blocks are generally most useful when a specific nerve
or limb is affected. Neuropathies with bilateral or multiple areas
of involvement may benefit from other forms of neuromodulation including
pharmacologic management, transcutaneous electrical stimulation
(TENS), or spinal cord stimulation.1,2
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Successful treatment outcomes involve numerous factors including
proper patient selection, understanding the anatomy, side effects,
and potential complications of each specific nerve block. A comprehensive
approach to chronic pain management has been shown to produce superior
outcomes.3 Nerve blocks, when appropriate, should
be considered part of the overall multidisciplinary treatment plan.
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Patients selected for nerve block therapy or regional anesthesia
should have an accurate diagnosis for the origin of their pain.
In some instances nerve blocks may aid in the diagnosis of certain acute
and chronic conditions. The relief of pain comes from the interruption
of nociceptive or pain sensory pathways, sympathetic blockade, or
somatosensory blockade. Regional anesthesia may be used to interrupt
the afferent limb of abnormal reflexes that contribute to the pathogenesis
of some pain syndromes. Regional anesthesia may block efferent sympathetic
outflow, which contributes to postoperative, post-traumatic, and
chronic pain syndromes with sympathetic involvement such as complex
regional pain syndrome (CRPS) or postherpetic neuralgia.4
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A complete history and physical evaluation of the patient should
be performed including review of laboratory studies, imaging studies,
medications, and allergies. Psychiatric and psychosomatic assessment
should be carried out when appropriate. Special attention should
be paid to anticoagulant medications, sensory loss or motor weakness
on physical examination. Complaints of sexual dysfunction, and bowel
or bladder problems should also be noted. Any abnormal findings
should be documented and may require further evaluation prior to
any interventional nerve blocks.
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The choice of local anesthetic (LA) used will affect the density
of the nerve ...