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Anesthesia: A look at local, regional and general anesthesia
From MayoClinic.com
Special to CNN.com

Anesthesia is the loss of sensitivity to pain brought about by various drugs (anesthetics). Anesthesia is used during many medical procedures, including surgical procedures. The type of anesthesia you receive depends on the procedure being performed and your physical and emotional status. Knowing the type of anesthesia you will receive before a medical procedure or surgery will help you know what to expect in terms of preparation, pain relief and recovery.

Types of anesthesia

Anesthesia can be categorized by the degree to which it suppresses consciousness and protective reflexes. Larger procedures often require greater amounts of anesthesia. From least to most, levels of anesthesia include: local, conscious sedation, regional and general. Determining the best choice for you depends on the anticipated nature and duration of the procedure, as well as your medical and psychological health. Discuss your options with your doctor.

Local anesthesia
Local anesthesia is used to block pain in a specific part of your body, allowing you to remain fully alert. The area that is anesthetized is usually small and superficial. Typically, a local anesthetic is used for dental work, skin biopsies or stitching up a cut. Sometimes a local anesthetic is used for a more extensive procedure in people for whom general or regional anesthesia is inadvisable.

For local anesthesia, an anesthetic is injected at or near the site of the procedure. The injection numbs the area to pain and any other sensation. Local anesthetics are generally of short duration. They come in different forms, including injections, sprays and ointments. Only rarely do they cause an allergic reaction.

Conscious sedation
Conscious sedation or intravenous (IV) sedation is used to relax you and make you feel sleepy. It generally includes intravenous administration of pain medication and a mild sedative to minimize any discomfort. These medications also cause temporary forgetfulness, so you may not remember what happens during the procedure.

Even though you may not remember anything that occurs during conscious sedation, you remain awake enough during that time to respond to questions and retain your protective reflexes. For example, if secretions accumulated in your throat, you would swallow or cough. This type of anesthesia is used for procedures such as colonoscopy, an exam of your colon and rectum. Conscious sedation is also frequently combined with regional anesthesia. 

Regional anesthesia
Regional anesthesia is used to block sensation in a particular region of your body, such as the lower half of your body, an eye, or an arm or leg. As with local anesthesia, you remain conscious during regional anesthesia. Often regional anesthesia is combined with conscious sedation, so you might not remember any of the procedure.

The anesthetic is injected around a single nerve or a network of nerves that serve the area involved in the surgical procedure. You receive the injection, which is generally painless, while lying on your back or side, or sitting.

To eliminate pain in the lower half of your body, spinal, epidural or caudal anesthetics may be injected near your spinal cord. These forms of anesthesia are often used for pelvic operations and for leg and hip surgery. Epidural anesthesia is often used during childbirth.

The main advantage of regional anesthesia is that it provides a high level of anesthesia to a selected region of the body while having little effect on other areas, such as your heart, lungs and brain. In regional anesthesia, your protective reflexes remain intact.

An additional benefit of regional anesthesia is that it helps control postoperative pain. That means you may require less pain medication after surgery and can avoid the nausea and grogginess that often result from those medications.

General anesthesia
General anesthesia is used for more extensive procedures or for procedures that aren't amenable to regional anesthesia. The medications used in general anesthesia are given intravenously or by inhalation. The drugs circulate in your bloodstream to all areas of your body, including your brain. They can suppress all of your protective reflexes, such as coughing, gagging and even breathing. Consequently, a general anesthetic requires the use of a mask or breathing tube while you're asleep.

Because general anesthetics affect all areas of your body, such as the heart and lungs, side effects from the medications are more common. However, most are temporary and can be managed by your medical team.

Before anesthesia: Answer questions carefully to ensure safety

Determining the type of anesthesia best suited to your needs requires open communication among you, your anesthesia provider and your surgeon. If you have any concerns or fears, make those known as early as possible so that they can be properly addressed.

At some point before your surgery, you can expect questions about:

  • Your current health. Any medical problems you might have — in particular heart, lung, kidney and endocrine conditions, such as diabetes — need to be discussed.
  • Any medications you take. To avoid potentially dangerous drug interactions, it's important to provide a list of all the medications you take or have taken recently, as well as any dietary supplements or herbal products you may be using. You may be instructed to take some of your medicines the day of your procedure.
  • Whether you smoke or consume alcohol. Smoking or alcohol consumption can influence the way an anesthetic works in your body during surgery. Knowing whether you smoke or drink alcohol allows your anesthesiologist to choose anesthetics that are better suited to your condition.
  • Any known allergies to food or medications. Some anesthetics include components of certain foods, such as albumin from eggs. Discussing food and drug allergies beforehand helps your anesthesiologist make important drug choices necessary for your surgical procedure.
  • Any previous experience with anesthesia that may have been unpleasant. Thanks to newer drugs and different techniques, unpleasant side effects from anesthesia, such as nausea and vomiting, can often be avoided.
  • Any adverse reactions to anesthesia by other family members. Although rare, adverse reactions to certain anesthetics can run in families. If someone in your family has had a serious reaction to anesthesia, you also may be at risk. Inform your doctor so that he or she can make appropriate adjustments in the anesthetic technique.
  • When you last ate. The risks of anesthesia are greater if you have food or liquid in your stomach, although small amounts of water or black coffee may be safe if taken a sufficient time before your procedure. Discuss this with your anesthesia provider or surgeon.

How safe is anesthesia?

The practice of anesthesia has changed remarkably in a relatively short time. Just 40 years ago, anesthesia was typically administered as drops of ether through a mask. A stethoscope and blood pressure cuff served as the primary monitoring tools.

Today, doctors have a greater understanding of how anesthesia affects the individual and can choose from many anesthetic drugs depending on the needs of the patient. Meanwhile, advances in monitoring equipment have dramatically reduced anesthesia-related complications. In the last decade alone, deaths due to anesthesia have dropped 25-fold, from 1 in 10,000 to 1 in 250,000.

Advances in monitoring include a device that determines whether a breathing tube placed in your windpipe (trachea) during general anesthesia is properly positioned. The device also measures whether you're receiving adequate ventilation during general anesthesia. Other monitors keep track of your heart rate, circulation, blood pressure, temperature, body fluid balance and other body functions.

In addition, shorter-acting drugs, more specific drugs and new intravenous drugs can minimize the nausea and vomiting that sometimes occur after anesthesia.

Awareness during surgery: Rare but concerning phenomenon

You may have heard frightening reports of people being awake (awareness) during surgery. Can this happen to you?

First, understand that none of the anesthetics described earlier, except general anesthesia, are meant to eliminate awareness. Awareness is good most of the time because it allows you to protect yourself.

For example, awareness allows you to cough or swallow when secretions accumulate in your throat. If you were unconscious, the secretions could enter your windpipe and go to your lungs.

Conscious sedation is often used to blunt or eliminate the memory of a procedure, but your memory isn't necessarily completely erased. Memories of awareness during conscious sedation or local or regional anesthesia are not too unusual and shouldn't concern you.

But what about awareness during general anesthesia? The beginning and ending portions of general anesthesia — those periods just before you lose consciousness and right after you wake up — are very similar to conscious sedation. Awareness is a normal part of those portions of a general anesthetic.

However, it's rare to have awareness during a general anesthetic while the surgery is taking place. In some extreme circumstances, such as profound blood loss or heart failure, your body may not be able to handle the effects of the anesthetic. In those circumstances, the anesthetic dose must be decreased to levels where consciousness may return.

The reassuring news is that even in those cases of awareness during anesthesia, the experience is usually not painful. If you do experience awareness during general anesthesia, be sure to discuss it with your anesthesia provider or surgeon.

June 16, 2006

© 1998-2006 Mayo Foundation for Medical Education and Research (MFMER). All rights reserved. A single copy of these materials may be reprinted for noncommercial personal use only. "Mayo," "Mayo Clinic," "MayoClinic.com," "Embody Health," "Reliable tools for healthier lives," "Enhance your life," and the triple-shield Mayo Clinic logo are trademarks of Mayo Foundation for Medical Education and Research. Terms of Use.

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