What you should know about anesthesia

Many procedures require anesthesia, and which of the four types you have can affect your recovery.

If you've ever had a tooth filled without Novocaine, you know the difference anesthesia can make. Anesthesia—whether it numbs your mouth or puts you into a full sleep—is designed to keep you comfortable during a procedure that otherwise might be hard to tolerate physically, emotionally, or both. "We have four goals: to see that you have no pain, that you're drowsy or unconscious, that your body is still so that the surgeon can work on it, and that you aren't left with bad memories of the procedure," says Dr. Kristin Schreiber, an anesthesiologist at Harvard-affiliated Brigham and Women's Hospital.

There are four basic kinds of anesthesia—local, which is typically administered to numb a small area; regional, which numbs a larger area, like your hand, arm, or foot; neuraxial (spinal or epidural), which is injected near the spine and numbs the lower half of your body; and general, which works in the brain to render you completely unconscious and unable to sense pain. The type used depends upon the procedure you're having, your state of health, and, often, your preferences.

1. Local anesthesia

Unless you've made it through life without having your wisdom teeth extracted or an injury that required stitches, you've probably had local anesthesia. Local anesthetics are injected near the area to be treated, and their effects are limited to a fairly small area. They are usually administered by a professional—a nurse, dentist, or doctor—who will make sure the area is numb. Giving local anesthesia actually does not require specialized training. Although you won't feel pain with a local, you may feel pressure. If you find that disturbing, you can be given a sedative to ease your anxiety.

2. Regional anesthesia

In regional anesthesia, local anesthetics are injected near clusters of nerves to numb a larger area, or region, of the body. A classic example is hand surgery, where a shot of numbing medicine near the nerves in the armpit makes the whole arm go numb for three to 24 hours, depending on the type of numbing medicine used.

3. Neuraxial anesthesia

Neuraxial anesthesia includes epidurals and spinals. In neuraxial anesthesia, numbing medicine is placed near the spinal roots, making an even larger part of the body numb than regional anesthesia does. Epidurals are commonly given to ease the pain of labor and childbirth or the pain with a large abdominal incision. Spinals, which block sensation to the abdomen and lower body, are frequently used for cesarean section and knee surgery.

With both regional and neuraxial anesthesia, you may be able to choose how conscious you'll be during the procedure. With minimal sedation, you'll be relaxed but aware of what's going on. Moderate sedation will send you into a "twilight sleep," in which you'll drift in and out of consciousness but can be easily aroused. With deep sedation, you are essentially fast asleep and unlikely to remember anything.

4. General anesthesia

Anesthesiologists use a combination of intravenous drugs that render you unconscious and unable to feel pain. You are also often given a drug to relax your muscles so that your body is still during the surgery. The anesthesiologist often inserts a tube in your trachea to allow him or her to help you breathe. Because general anesthesia affects so many body systems, it is associated with more side effects than regional anesthesia, including nausea and delirium, although these can be minimized. "The effects of general anesthesia last longer in older people. It may take longer to restore memory, and they may have more delirium," Dr. Schreiber says.