Medical Encyclopedia


Medical Encyclopedia

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Definition    Return to top

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

Information    Return to top

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 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 or applied to the skin as a gel.

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 near 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 is commonly used 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 the surgery is over, the process is reversed, and you will wake up shortly thereafter in the recover room.


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.


All types of anesthesia carry some risk, although major side effects and complications are uncommon. 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. This is due to better anesthetia drugs and better monitoring techniques.

Risks from any type of anesthesia include:

Risks from local and regional anesthesia include:

Risks from general anesthesia may include:

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, such as open heart surgery. The complication is called postoperative cognitive dysfunction (POCD).

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


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.

References    Return to top

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.

Update Date: 5/15/2009

Updated by: Daniel B. Sack, M.D., Private Practice specializing in Anesthesiology, Thomas Johnson Surgery Center, Frederick, MD. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

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