Spinal and epidural procedures are both regional anesthetics that anesthetize a particular region of the body. (Under general anesthetic the patient is unconscious.)
Spinal anesthetics are used primarily for elective cesarean sections, where the duration of the surgery is known. Spinal anesthetic involves a single injection of anesthetic medication directly into the fluid surrounding the spinal cord. Once the drug is injected, it is impossible to extend the duration of a spinal anesthetic. The effects of spinal anesthetic can last for one to 10 hours.
An epidural is administered in a similar fashion but, in contrast to a spinal, an epidural involves placing a catheter into the epidural space (located near the spinal cord). Medication is injected through the catheter to numb the nerves. Due to the presence of the catheter, epidural anesthetic can be made to last as long as needed and the amount of medication can also be altered. Epidural is used for labor since delivery is unpredictable in length and intensity.
If you are given an epidural for labor, and need to have an emergency cesarean section, a stronger medication can be injected through the epidural catheter to provide sufficient anesthesia for the surgery.
Dr. William Camann is the director of obstetric anesthesia at the Brigham and Women's Hospital in Boston. He is also an associate professor of anesthesia at Harvard Medical School, and past-president of the Society for Obstetric Anesthesia and Perinatology. An internationally recognized authority on obstetric anesthesia and pain control during childbirth Dr. Camann is the co-author of Easy Labor, Every Woman's Guide to Choosing Less Pain and More Joy During Childbirth (Random House/Ballantine Books, 2006). You can find out more about his book at easylabor.net