- What is general anesthesia
- How does general anesthesia work
- General anesthesia drugs
- General anesthesia risks
- General anesthesia side effects
What is general anesthesia
General anesthesia is treatment with certain medicines that puts you into a deep sleep so you do not feel pain during surgery. After you receive these medicines, you will not be aware of what is happening around you.
General anesthesia include analgesia (relief from or prevention of pain), paralysis (muscle relaxation), amnesia (loss of memory), or unconsciousness. A patient under the effects of anesthetic drugs is referred to as being anesthetized.
The purpose of general anesthesia can be distilled down to three basic goals or end points:
- Hypnosis (a temporary loss of consciousness and with it a loss of memory). In a pharmacological context, the word hypnosis usually has this technical meaning, in contrast to its more familiar lay or psychological meaning of an altered state of consciousness not necessarily caused by drugs.
- Analgesia (block pain sensation which also blunts autonomic reflexes)
- Muscle relaxation
The ideal general anesthetic drug would provide hypnosis, amnesia, analgesia, and muscle relaxation without undesirable changes in blood pressure, pulse or breathing.
Anesthesia enables the painless performance of medical procedures that would cause severe or intolerable pain to an unanesthetized patient.
How does general anesthesia work
General anesthesia suppresses central nervous system activity and results in unconsciousness, complete muscle paralysis and total lack of sensation 1). The goal is to make and keep a person completely unconscious (or “asleep”) during the operation, with no awareness or memory of the surgery. General anesthesia can be given through an IV (which requires sticking a needle into a vein, usually in the arm) or by inhaling gases or vapors by breathing into a mask or tube. General anesthesia delivered intravenously will act quickly and disappear rapidly from the body. This allows patients to go home sooner after surgery. Inhaled anesthetics may take longer to wear off.
Surgeons use general anesthesia when they operate on internal organs and for other invasive or time-consuming procedures such as back surgery. Without general anesthesia, many major, life-saving procedures would not be possible, including open-heart surgery, brain surgery and organ transplants.
General anesthetics typically are very safe. But they can pose risks for some patients, such as the elderly or people with chronic illnesses such as diabetes. Also, side effects may linger for several days in some patients, especially the elderly and children.
Although you may be able to talk to the anesthesiologist a day or two prior to the operation, you might not meet until that day. Either way, the anesthesiologist will go over your medical history and information thoroughly, so that he or she can make the right choice regarding anesthetic medications tailored to your individual needs.
To ensure your safety during the surgery, you’ll need to answer all of the anesthesiologist’s questions as honestly and thoroughly as possible. Things that may seem harmless could interact with or affect the anesthesia and how you react to it.
The anesthesiologist might order additional tests (such as X-rays or blood or laboratory tests) to help figure out the best possible personalized anesthetic plan for you.
- your current and past health
- your family’s health
- any medications, supplements, or herbal remedies you are taking (consider bringing a list of exactly what you take, detailing how much and how often)
- any previous reactions you or any blood relative has had to anesthesia
- any allergies (especially to foods, medications, or latex) you may have
- whether you smoke, drink alcohol, or take recreational drugs.
This will help your anesthesiologist choose the medications that will be the safest for you.
How you prepare for a general anesthesia
General anesthesia relaxes the muscles in your digestive tract and airway that keep food and acid from passing from your stomach into your lungs. Always follow your doctor’s instructions about avoiding food and drink before surgery.
Fasting is usually necessary starting about six hours before your surgery. You may be able to drink clear fluids until a few hours prior.
Your doctor may tell you to take some of your regular medications with a small sip of water during your fasting time. Discuss your medications with your doctor.
You may need to avoid some medications, such as aspirin and some other over-the-counter blood thinners, for at least a week before your procedure. These medications may cause complications during surgery.
Some vitamins and herbal remedies, such as ginseng, garlic, Ginkgo biloba, St. John’s wort, kava and others, may cause complications during surgery. Discuss the types of dietary supplements you take with your doctor before your surgery.
If you have diabetes, talk with your doctor about any changes to your medications during the fasting period. Usually you won’t take oral diabetes medication the morning of your surgery. If you take insulin, your doctor may recommend a reduced dose.
If you have sleep apnea, discuss your condition with your doctor. The anesthesiologist or anesthetist will need to carefully monitor your breathing during and after your surgery.
Eating and Drinking Before Anesthesia
The anesthesiologist, surgeon, or someone on the nursing staff will give you instructions about not eating or drinking before surgery. It’s important to make sure you don’t eat anything prior to surgery (usually nothing after midnight the day before the operation). You’ll get specific instructions based on your age, medical condition, and the time of day of the procedure.
Why is eating before surgery an issue? Because the body normally has reflexes that prevent food from being aspirated (or inhaled) into the lungs when it’s swallowed or regurgitated (thrown up). But anesthetic medications can suspend these reflexes, which could cause food to become inhaled into the lungs if there is vomiting or regurgitation under anesthesia.
Sometimes, though, the anesthesiologist will say it’s OK to drink clear liquids or take specific medications a few hours before surgery.
In the Operating Room
If general anesthesia is used, the anesthesiologist will start transitioning you from the normal awake state to the sleepy state of anesthesia. This is called induction, which is usually done by either injecting medicine through an IV or by inhaling gases through a mask.
If, like lots of people, you’re afraid of needles, the good news is that you may not have to get one while awake. Anesthesiologists often will begin the induction process by using a breathing mask to help you relax. The mask delivers medication to make you sleepy before and during the surgery. That way, you won’t be awake when the IV is inserted for general anesthesia or when a shot is given to numb a certain part or area of the body for local or regional anesthesia.
When using general anesthesia, the anesthesiologist will monitor your vital signs, continue to deliver anesthesia, and keep you as comfortable as possible throughout the operation.
To help you breathe and/or to help deliver general anesthesia during the operation, the anesthesiologist might use an endotracheal tube (a plastic tube that’s placed into the windpipe through the mouth or nose) or laryngeal mask airway (or LMA — a mask with a tube that fits into the back of the mouth).
During the procedure
Your anesthesiologist usually delivers the anesthesia medications through an intravenous line in your arm. Sometimes you may be given a gas that you breathe from a mask. Children may prefer to go to sleep with a mask.
Once you’re asleep, the anesthesiologist may insert a tube into your mouth and down your windpipe. The tube ensures that you get enough oxygen and protects your lungs from blood or other fluids, such as stomach fluids. You’ll be given muscle relaxants before doctors insert the tube to relax the muscles in your windpipe.
Your doctor may use other options, such as a laryngeal airway mask, to help manage your breathing during surgery.
Someone from the anesthesia care team monitors you continuously while you sleep. He or she will adjust your medications, breathing, temperature, fluids and blood pressure as needed. Any issues that occur during the surgery are corrected with additional medications, fluids and, sometimes, blood transfusions.
Blood transfusions may sometimes be necessary, such as during complex surgeries. The anesthesia care team monitors your condition and delivers blood transfusions when needed. Blood transfusions may involve risks. These risks are greater in people who are older, have low red blood cell volume or are undergoing complex heart surgeries.
Once the operation or procedure is over, you’ll be taken to the recovery room or PACU (post-anesthesia care unit). In the PACU, nurses and the anesthesiologist will monitor your condition very closely to make sure you are making a smooth and comfortable transition from an anesthetized state to an awakened state.
If you had general anesthesia or were sedated, don’t expect to be fully awake right away — it may take a while and you may doze off for a bit. It usually takes about 45 minutes to an hour to recover completely from general anesthesia. In some cases, this period may be a bit longer depending on medications given during or after surgery.
Although every person has a different experience, you may feel groggy, confused, chilly, nauseated, scared, alarmed, or even sad as you wake up. Depending on the procedure or surgery, you may also have some pain and discomfort afterward, which the anesthesiologist can relieve with medications. When you have recovered from the anesthesia, you’ll be evaluated to make sure you’re ready to leave the recovery room.
In many outpatient procedures, people are allowed to come home soon after the surgery is done. Before you leave the hospital, you’ll receive instructions for further recuperation at home and for a follow-up visit with the surgeon. Talk to the surgeon and/or the anesthesiologist about what to expect after the surgery and how you can stay as comfortable as possible.
Anesthesia is very safe. In today’s hospitals and surgery centers, highly trained professionals use a wide variety of modern medications and extremely capable monitoring technology to ensure that people are stable and as comfortable as possible before, during, and after their procedure.
After the procedure
When the surgery is complete, the anesthesia medications are stopped, and you slowly wake either in the operating room or the recovery room. You’ll probably feel groggy and a little confused when you first wake. You may experience common side effects such as:
- Dry mouth
- Sore throat
- Mild hoarseness
You may also experience other side effects after you awaken from anesthesia, such as pain. Side effects depend on your individual condition and the type of surgery. Your doctor may give you medications after your procedure to reduce pain and nausea.
General anesthesia drugs
A general anesthetic (or anaesthetic) is a drug that can bring about a reversible loss of consciousness. Anesthesiologist (or anaesthetist) administers these drugs to induce or maintain general anesthesia to facilitate surgery. Some of these drugs are also used in lower dosages for pain management. The biological mechanisms of the action of general anesthetics are not well understood.
Mode of administration. Drugs given to induce general anesthesia can be either as gases or vapors (inhalational anesthetics) or as injections (intravenous anesthetics or even intramuscular). It is possible to deliver anesthesia solely by inhalation or injection, but most commonly the two forms are combined, with an injection given to induce anesthesia and a gas used to maintain it.
Inhalation general anesthetic
Inhalational anaesthetic substances are either volatile liquids or gases, and are usually delivered using an anesthesia machine. An anesthesia machine allows composing a mixture of oxygen, anesthetics and ambient air, delivering it to the patient and monitoring patient and machine parameters. Liquid anesthetics are vaporized in the machine. All of these agents share the property of being quite hydrophobic (i.e., as liquids, they are not freely miscible—or mixable—in water, and as gases they dissolve in oils better than in water).
Many compounds have been used for inhalation anaesthesia, but only a few are still in widespread use.
- Desflurane, isoflurane and sevoflurane are the most widely used volatile anaesthetics today.
They are often combined with nitrous oxide. Older, less popular, volatile anaesthetics, include halothane, enflurane, and methoxyflurane. Researchers are also actively exploring the use of xenon as an anaesthetic.
Injection general anesthetic
Injectable general anesthetics are used for the induction and maintenance of a state of unconsciousness. Anaesthetists prefer to use intravenous injections, as they are faster, generally less painful and more reliable than intramuscular or subcutaneous injections.
Among the most widely used drugs are:
- Barbiturates such as methohexital and thiopentone/thiopental
- Benzodiazepines such as midazolam
- Ketamine is used in the UK as “field anaesthesia”, for instance at a road traffic incidents or similar situations where an operation must be conducted at the scene or when there is not enough time to move to an operating room, while preferring other anaesthetics where conditions allow their use. It is more frequently used in the operative setting in the US.
Benzodiazepines are sedatives and are used in combinations with other general anesthetics.
General anesthesia risks
General anesthesia today is very safe. In very rare cases, general anesthesia can cause complications (such as strange heart rhythms, breathing problems, allergic reactions to medications, and even death). The likelihood of a complication occurring is proportional to a variety of factors related to the patient’s health, the kind of procedure (complexity of the surgery being performed) and the type of anesthesia used. Be sure to talk to your doctor, surgeon, and/or anesthesiologist about any concerns.
Most complications can be prevented by giving the anesthesiologist complete information before the surgery about things like:
- your current and past health (including diseases or conditions such as recent or current colds, or other issues such as snoring or depression)
- any medications (prescription and over-the-counter), supplements, or herbal remedies you are taking
- any allergies (especially to foods, medications, or latex) you may have
- whether you smoke, drink alcohol, or take any recreational drugs
- any previous reactions you or any family member has had to anesthesia
To ensure your safety during the surgery or procedure, it’s extremely important to answer all of the anesthesiologist’s questions as honestly and thoroughly as possible. Things that may seem harmless could affect how you react to the anesthesia.
It’s also important that you follow the doctor’s recommendations about what not to do before the surgery. You probably won’t be able to eat or drink (usually nothing after midnight the day before) and may need to stop taking herbal supplements or other medications for a certain period of time before surgery.
You can rest assured that the safety of anesthetic procedures has improved a lot over the years, thanks to advances in technology and the extensive training anesthesiologists receive. The more informed, calm, and reassured you are about the surgery and the safety of anesthesia, the easier the experience will probably be.
General anesthesia side effects
General anesthesia is overall very safe; most people, even those with significant health conditions, are able to undergo general anesthesia itself without serious problems.
General anesthetics side effects—such as dangerously low blood pressure—are much less common than they once were. Still, as with any medical procedure, some risks exist. To minimize these risks, specialized doctors called anesthesiologists carefully monitor unconscious patients and can adjust the amount of anesthetic the patients receive.
In fact, your risk of complications is more closely related to the type of procedure you’re undergoing and your general physical health, rather than to the type of anesthesia.
Older adults, or those with serious medical problems, particularly those undergoing more extensive procedures, may be at increased risk of postoperative confusion, pneumonia, or even stroke and heart attack.
Specific conditions that can increase your risk of complications during surgery include:
- Obstructive sleep apnea
- High blood pressure
- Other medical conditions involving your heart, lungs or kidneys
- Medications, such as aspirin, that can increase bleeding
- History of heavy alcohol use
- Drug allergies
- History of adverse reactions to anesthesia
These risks are generally related to the surgery itself, not the anesthesia.
Common Side Effects of General Anesthesia
You will most likely feel disoriented, groggy, and a little confused when waking up after surgery. Some other common side effects, which should go away fairly quickly, include:
- nausea or vomiting, which can usually be alleviated with anti-nausea medication
- chills or shakiness
- sore throat (if a tube was used to help with breathing).
What is Anesthesia awareness ?
Estimates vary, but about 1 or 2 people in every 10,000 may be partially awake during general anesthesia and experience what is called unintended intraoperative awareness. It is even rarer to experience pain, but this can occur as well.
Because of the muscle relaxants given before surgery, people are unable to move or speak to let doctors know that they are awake or experiencing pain. For some patients, this may cause long-term psychological problems, similar to post-traumatic stress disorder.
This phenomenon is so rare that it’s difficult to make clear connections. Some factors that may be involved include:
- Emergency surgery
- Cesarean delivery
- Use of certain medications
- Heart or lung problems
- Daily alcohol use
- Lower anesthesia doses than are necessary used during procedure
- Errors by the anesthesiologist, such as not monitoring the patient or not measuring the amount of anesthesia in the patient’s system throughout the procedure.
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