Anesthesia is the delivery of medicine to prevent you from feeling pain during surgery and other medical or dental procedures.

Anesthesia may be given to you by a special doctor called an anesthesiologist or other health care provider. There are three main forms of anesthesia:

• Local anesthesia
• Regional anesthesia
• General anesthesia

Local anesthesia numbs only the part of your body that is hurt or being worked on. You are awake, but won't feel any pain. Most of the time, a needle is used to inject the medicine under the skin. Sometimes it is delivered through a nasal spray.

You may receive local anesthesia when you get stitches, have a tooth pulled, or when your doctor removes a small piece of skin for a biopsy.

Regional anesthesia numbs a large area, such as an entire arm, leg, or the entire lower half of your body. An anesthesiologist injects the medicine into a group of nerves so you no longer feel pain. You are awake, but you may be given medicine called a sedative to make you feel sleepy and less anxious.

Two common types of regional anesthesia include:

• Epidural anesthesia
• Spinal anesthesia

Epidural anesthesia is commonly to prevent pain during childbirth. The anesthesiologist injects the medicine into the lower back in the area surrounding the spine. This type of anesthesia causes you to lose feeling in the lower half of the body.

Spinal anesthesia goes directly into the spinal canal. It also causes you to lose feeling in the lower part of your body. You may receive spinal anesthesia if you are having a hernia repair, certain prostate surgeries, or another medical procedure on the lower half of your body.

General anesthesia is used to temporarily put you into a deep sleep so you don't feel pain during surgery. You will not be aware of what is going on around you. A number of different medicines may be used. Sometimes, you breathe in the medicine through a gas mask or breathing tube. The anesthesiologist may also give you the medicine through a vein. During general anesthesia, the health care team carefully watches your vital signs and body functions, including your breathing and brain activity. After surgery is over, you will be given medicines to reverse the effects of the anesthesia, so you wake up.

HOW IT WORKS

When you hurt, pain signals travel up the spinal cord, through your nervous system, and to the brain. The medicines used during local and regional anesthesia temporarily blocks nerve signals in the area, so you don't feel the pain. General anesthesia shuts down the brain's pain-processing center, so your body doesn't recognize the pain signals.

RISKS

All types of anesthesia carry some risk. Local anesthesia is the safest. General anesthesia affects the entire body, so side effects are more common. However, the American Society of Anesthesiologists says that complications due to anesthesia have dropped dramatically over the last 25 years.

Risks from any type of anesthesia include:

• Allergic reaction to the medicines used
• Breathing problems

Risks from local and regional anesthesia include:

• Long-term nerve damage (rare)
• Temporary weakness or paralysis in the area that received the anesthesia

Risks from general anesthesia include:

• Irregular heartbeat
• Heart attack (rare)
• Nausea and vomiting
• Stroke (rare)
• Temporary mental confusion (delirium)

Delirium is most common in older adults. Studies have linked general anesthesia to long-term problems in mental function in older adults who have certain types of surgery. The complication is called postoperative cognitive dysfunction (POCD).

Medicines can be given before or after anesthesia to help prevent nausea and vomiting.

SAFETY TIPS

Make sure you tell your health care providers about all the medicines you take. This includes over-the counter drugs, vitamins, and supplements.

Do not drink or smoke before surgery. Cigarettes and alcohol can change the way the anesthesia drugs work.

American Society of Anesthesiologists Task Force on Postanesthetic Care. Practice guidelines for postanesthetic care: a report by the American Society of Anesthesiologists Task Force on Postanesthetic Care. Anesthesiology. March 2002; 96(3): 742-52.

Miller RD. Miller's Anesthesia. 6th ed. Orlando, Fl: Churchill Livingstone; 2005.

Anesthetic management and one-year mortality after noncardiac surgery. Anesth Analg. 2005 Jan;100(1):4-10.

Longitudinal assessment of neurocognitive function after coronary-artery bypass surgery. N Engl J Med. 2001 Feb 8;344(6):395-402.