The lumbar sympathetic nerves lie in front of the spine in the lower back. They are approached from behind and the injection is done under X-ray guidance with the use of a fluoroscope. The patient is placed on the stomach, some medication is usually given to sedate the patient, and the skin is cleansed with an antiseptic solution. The injection site on the skin is identified and anesthetized, and a larger needle is placed near the nerves in front of the spine. A small amount of contrast solution is injected first to assure that the tip of the needle is in proper position, and then the anesthetic solution is injected to bathe the sympathetic nerves. Afterwards, the skin temperature on the blocked side increases, and sweating is inhibited. The pain relief that follows often lasts longer than the other effects of the anesthetic. Many times, repeated injections may have cumulative benefit.