Here is a good site...........

http://www.clevelandclinic.org/health/health-info/docs/0300/0325.asp?index=4417
What is a nerve block?
Nerve block is a general term, but it basically means the injection of a local anesthetic or a
neurolytic agent into or near a peripheral nerve, a sympathetic nerve plexus, or a local
pain-sensitive trigger point.

Who can be helped by nerve blocks?
Nerve blocks can help those who suffer from:

 a.. Neck pain
 b.. Low back pain
 c.. Sciatica resulting from herniated discs
 d.. Lumbar canal stenosis
 e.. Complex regional pain syndrome (reflex sympathetic dystrophy)
 f.. Pain arising from peripheral vascular disease
 g.. Shingles pain
 h.. Myofascial pain syndrome
 i.. Cancer pain
Basic considerations for using nerve blocks
The proper use of nerve blocks to treat pain requires a specially trained physician with a
thorough understanding of pain and its syndromes. It is essential that a patient is selected for
nerve block therapy only after an accurate diagnosis of the source of the pain is made. The
examination may include a complete medical history, physical examination, laboratory studies,
and a complete psychiatric and psychosomatic assessment.

How does a nerve block work?
Nerve blocks relieve pain by interrupting pain sensory pathways and preventing them from
reaching the brain. A local anesthetic is used to temporarily block the transmission of pain
along these pathways. Two types of sensory pathways are sympathetic nerve plexus and
somatosensory nerve.

What are the types of nerve blocks?

 a.. Trigger point injection - injection (shot) of small amounts of local anesthetic and
steroid in the area of the muscle where you have pain or tenderness.
 b.. Epidural steroid injection - injection of a small amount of steroid medication near nerves
in your lower back.
 c.. Facet joint injection - injection of a small amount of local anesthetic near facet joints
(located on the side or your spine, away from the spinal cord).
 d.. Stellate ganglion block - injection of local anesthetic around a group of nerves (found in
the neck area).
 e.. Lumbar sympathetic block - an injection of local anesthetic around a group of nerves in
your lower back (lumbar area).
 f.. Intercostal nerve block - an injection of local anesthetic in the area between the ribs.
How long does the pain relief last after a nerve block is given?
Nerve blocks can be performed as a single injection, continuous infusion, or nerve destruction.
Nerve blocks may relieve pain from several hours to several months. In many cases, nerve blocks
are performed in conjunction with a rehabilitation program and can provide the window of
opportunity to proceed with effective rehabilitation.

How effective are nerve blocks?
It is important to remember that no single treatment technique is guaranteed to produce complete
pain relief. Nerve blocks are very effective in providing temporary pain control, but they are
only part of a total pain management program. For patients with chronic pain conditions, a
multifaceted approach (treatment that includes rehabilitation and psychological intervention) is
essential. A top priority of the pain management program is restoring function of the affected
area.

What are the side effects?
Some people have allergic reactions to local anesthetics, but such reactions are rare. People
who have allergic reactions to local anesthetics should not receive injections.

Steroids are frequently used in nerve blocks and can cause fluid retention, increased appetite,
blood pressure and blood sugar fluctuations, and mood swings.

The use of morphine or morphine derivatives can cause constipation, urinary retention, pruritis
(itching), nausea, and vomiting.

The destruction of nervous tissue can cause partial loss of motor or sensory functions.

When should a nerve block not be performed?
A nerve block should not be performed for patients who are on anticoagulant therapy with heparin
or coumadin. These medications can increase the risk of bleeding. In addition, nerve blocks
should not be performed for patients who have an active infection around the area of pain or for
patients who are allergic to local anesthetics or steroids.