Within the body, there are nerve fibers that arise from the spinal cord that help regulate blood pressure and heart rate, along with a variety of other functions. These nerve fibers are called sympathetic nerve fibers and they form a part of the autonomic nervous system. Some of these sympathetic nerve fibers lie around the lumbar spine and are involved in regulating the functions of the blood vessels in the lower part of the body, along with other organs such as the bladder. A lumbar sympathetic block is where the function of these nerves is completely blocked off using a local anesthetic agent. This is called neurolysis.
A lumbar sympathetic block is performed in a variety of clinical conditions that cause pain, swelling, and alteration in the normal physiology of the lower extremities. Some conditions include peripheral vascular disease, reflex sympathetic dystrophy or complex regional pain syndrome, herpes zoster of the legs, phantom pain following limb amputation, and even pain due to cancer.