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General anesthesia
By Mayo Clinic staffOriginal Article: http://www.mayoclinic.com/health/anesthesia/MY00100
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Definition
General anesthesia is a treatment that renders you unconscious during medical procedures, so you don't feel or remember anything that happens. General anesthesia is commonly produced by a combination of intravenous drugs and inhaled gasses (anesthetics).
The "sleep" you experience under general anesthesia is different from regular sleep. The anesthetized brain doesn't respond to pain signals or surgical manipulations.
The practice of general anesthesia also includes controlling your breathing and monitoring your body's vital functions during your procedure. General anesthesia is administered by a specially trained physician, called an anesthesiologist, often in conjunction with a certified registered nurse anesthetist.
Why it's done
Your doctor may recommend general anesthesia for procedures that:
- Take a long time
- Affect your breathing, such as chest or upper abdominal surgery
- Require you to be in an uncomfortable position
Other forms of anesthesia may provide light sedation or use injections to numb a region of your body selectively.
Risks
Most healthy people don't have any problems with general anesthesia. However, as with most medical procedures, there is a small risk of long-term complications and, rarely, death. Specific complications are related to the type of procedure and your general physical health.
Additionally, the following factors can increase your risk of complications:
- Medical conditions involving your heart, lungs or kidneys
- Medications, such as aspirin, that can increase bleeding
- Smoking, which increases the likelihood of breathing problems
- Alcohol use, which may predispose you to liver damage
- Family history of adverse reactions to anesthesia
- Food or drug allergies
- Sleep apnea
- Obesity
The following complications are rare and occur more frequently in older adults or in people who have medical problems:
- Temporary mental confusion
- Lung infections
- Stroke
- Heart attack
- Death
Anesthesia awareness
Estimates vary, but about 1 or 2 people in every 1,000 may wake up briefly while under general anesthesia. In most cases, the person is simply aware of his or her surroundings and doesn't feel any pain. However, some people experience excruciating pain and develop long-term psychological problems.
The following factors appear to make this phenomenon — also called unintended intraoperative awareness — more likely:
- Emergency surgery
- Long-term use of anticonvulsants, opiates, tranquilizers or cocaine
- Heart or lung problems
- Daily alcohol use
How you prepare
General anesthesia blunts your body's natural inclination to retain food in your stomach and keep it out of your lungs. That's why it's important to follow your doctor's instructions about when to stop eating and drinking prior to surgery. In most cases, you should start fasting about six hours before your procedure.
Your doctor may tell you to take certain medications with a small sip of water during your fasting time. You may need to avoid some medications, such as blood thinners like aspirin, for at least a week before your procedure. Some vitamins and herbal remedies also keep your blood from clotting normally, so discuss the types of dietary supplements you take with your doctor.
If you have diabetes, talk with your doctor about altering your diabetes medication during the fasting period. Usually you will not take oral diabetes medication the morning of surgery, and if you take insulin a reduced dose will be recommended.
If you have sleep apnea and use a continuous positive airway pressure (CPAP) machine bring it with you to the surgery. As you awaken from anesthesia the CPAP machine can help you breathe more normally.
What you can expect
Before general anesthesia
Before you undergo general anesthesia, a medical professional specially trained to deliver anesthetics will talk with you and may ask questions about:
- Your health history
- Prescription medications, over-the-counter medications and herbal supplements you take
- Allergies
- Your past experiences with anesthesia
The information you provide will help the anesthesia specialist choose the drugs that will work best and be safest for you.
During general anesthesia
In most cases, the anesthesia is started with medication delivered through an intravenous line in your arm, but sometimes it can be started with a gas that you breathe from a mask. For example, children who are afraid of needles may prefer to go to sleep with a mask. Once you are asleep, a tube may be inserted into your mouth and down your windpipe to ensure you get enough oxygen and to protect your lungs from blood or body secretions, such as from your stomach. In some cases this breathing tube isn't needed, which reduces your chance of a sore throat after surgery.
A member of the anesthesia care team monitors you continuously during your procedure, adjusting your medications, breathing, temperature, fluids and blood pressure as needed. Any abnormalities that occur during the surgery are corrected by administering additional medications, fluids and, sometimes, blood transfusions.
After general anesthesia
When the surgery is complete, the anesthesia drugs are discontinued, and you gradually awaken either in the operating room or the recovery room. You'll probably feel groggy and a little confused when you first awaken. Other common side effects include:
- Nausea
- Vomiting
- Dry mouth
- Sore throat
- Shivering
- Sleepiness
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