The epidural space lies just outside the special covering or dura, which encloses the spinal canal. An 'epidural' is a type of regional anesthetic in which a needle is positioned between the bones of the spine to allow the anesthesiologist to insert a small plastic tube (or catheter) into the epidural space. The needle is then removed and local anesthetic is injected through the catheter. This local anesthetic moves (or diffuses) across the dura. into the spinal canal, and temporarily stops the spinal nerves from working, so that sensation and movement in the area supplied by the nerves does not occur. When the effect of the local anesthetic wears off, sensation and movement will return. If a weaker solution of local anesthetic is used, then only painful sensations will be blocked.
This is very useful for controlling pain and is called epidural analgesia. Often continuous infusions of local anesthetic solutions are used, which allows the effect to be maintained as long as required. The catheter may be placed in the upper back (thoracic spine) or the lower back (lumbar spine), depending on where the effect is needed. This is a very useful and safe procedure, when performed with appropriate care by an experienced anesthesiologist.