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General anesthesia is the administration of general anesthetic agents that make a person unconscious and unable to feel pain - often used during operative procedures.
The combination of these anesthetic agents - intravenous drugs and inhaled gasses - is intended to induce:
Anesthesiologists (doctors who specialize in anesthesia) as well as certified registered nurse anesthetists (CRNA) are typically in charge of ensuring that an optimal combination of these agents are given to the patient during surgery.
Attempts to make a general anesthetic were common in ancient Egypt, China and Babylonia.
But it was not until major scientific advancements were made in the late 19th century and the discovery of the germ theory of disease that antiseptic techniques began to develop.
Gradually a better understanding of pharmacology and physiology eventually led to more effective means of controlling of pain and the development of general anesthesia.
According to Medilexicon's medical dictionary1, general anesthesia is:
"loss of ability to perceive pain associated with loss of consciousness produced by intravenous or inhalation anesthetic agents; may include amnesia and muscle relaxation."
Even though the biochemical mechanism of action of anesthetics is not very well understood, it is thought that they are able to induce unconsciousness by affecting various sites of the central nervous system (CNS).
However, it is known that general anesthesia affects or interrupts the function of the cerebral cortex, thalamus, reticular activating system, and spinal cord.
The majority of general anesthetics nowadays are administered with a needle, by intravenous injection, or even inhaled in some cases.
Patients who are given general anesthesia have to be very carefully monitored for any changes in blood pressure, pulse, or breathing.
In some cases a tube may be inserted into the patients windpipe to protect the lungs and make breathing easier.
A study carried out by a team from Harvard Medical School, Weill Cornell Medical college and the Massachusetts Institute of Technology found that undergoing general anesthesia is more like a coma than a deep sleep2.
For small areas of the body that need to be numbed, applying local anesthesia is normally sufficient.
Procedures that typically require the administration of general anesthesia include those that:
General anesthesia is considered to be relatively safe because of modern safety standards and equipment. Complications are not that common although they can occur.
In 1937 Arthur Ernest Guedel classified the four stages of anesthesia:
Stage 1 "induction" - patients can talk in this stage but they begin to slowly lose consciousness.
Stage 2 "excitement stage" - the patient completely loses consciousness and may experience an irregular heart rate, there may also be uncontrolled movements.
Stage 3 "surgical anesthesia" - the skeletal muscles begin to relax and eye movement stops. The patient is unconscious and ready for surgery at this point.
Stage 4 "overdose" - at this stage too much medication has been administered and the patient experiences severe brain stem or medullary depression - which can be fatal without support.
For the most part, healthy adults should not have any issues with general anesthesia apart from some mild and temporary symptoms. There is a very small risk of long-term complications occurring and the risk depends on the form of surgery the patient is undergoing. Rarely, general anesthesia can cause lung infections, stroke, heart attack, and even death.
Health conditions or factors that increase the risk of complications, include:
Researchers at the University of Bordeaux, France, reported that elderly people who undergo general anesthesia have a 35% higher risk of eventually developing dementia4.
The Mayo Clinic reported that children who undergo general anesthesia many times are more likely to develop ADHD5 (attention-deficit hyperactivity disorder).
Very few people who receive general anesthesia undergo what is known as anesthesia awareness - where they are aware of their surroundings, but do not feel any pain.
Up to 2 in every 1,000 patients under general anesthesia wake up during their operation6, German researchers reported in the journal Deutsches Ärzteblatt International.
In extremely rare cases people can feel pain during surgery, this phenomenon is called unintended intraoperative awareness. The pain is usually unbearable, but because because of muscle relaxants that are given to the patient before surgery, they are not able to tell the surgeon about their distress.
People who experience unintended intraoperative awareness may go on to develop psychological problems, such as post-traumatic stress disorder.
Written by Joseph Nordqvist
Copyright: Medical News Today
Not to be reproduced without the permission of Medical News Today.
1. Medilexicon's medical dictionary.
2. "General Anesthesia More Like Coma Than Sleep", Medical News Today.
3. "Patients With Sleep Apnea Undergoing Joint Replacement Have Improved Outcomes With Regional Anesthesia", Medical News Today.
4. "General Anesthesia Raises Dementia Risk Among Elderly Patients", Medical News Today.
5. "Anesthesia Exposure Linked To ADHD In Children", Medical News Today.
6. "Awake Despite Anesthesia", Medical News Today.
Visit our Pain / Anesthetics category page for the latest news on this subject.
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10 Dec. 2013. <http://www.medicalnewstoday.com/articles/265592>
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