Also known as neuraxial anesthesia, a spinal or epidural anesthetic is used for lower abdominal, pelvic, rectal, or lower extremity surgery. This type of anesthetic involves injecting anesthetic medication into the spinal or epidural space, which surrounds the spinal cord. The injection causes numbness in an area of the body supplied by the nerves that are blocked by the anesthetic. Usually, but not always, a spinal anesthetic involves a single injection of a medication, while an epidural anesthetic involves placement of a small catheter (hollow tube). Epidural anesthesia may also be used for the purpose of controlling pain both during and after surgical procedures, including those involving the upper abdomen or chest, or for management of labor pain. Possible side effects include headache, back pain, convulsions, infection, persistent numbness, weakness or pain, or unconsciousness necessitating general anesthesia.