Guide to General Anesthesia: What You Need to Know Before Going Under
General Anesthesia: What You Need to Know
For some procedures and surgeries, you may have a choice regarding the type of anesthesia used. Many times, though, the only good choice will be general anesthesia.
In this article I will give you a broad introduction to terminology, procedure, and what to expect.
General anesthesia means loss of consciousness.
If you are "under" with general anesthesia, you cannot feel, see, or hear anything, and you do not respond to even painful stimuli.
What to Expect Before Surgery
After checking in with a nurse and having an IV placed, you will meet your anesthesiologist to discuss your anesthetic. Midazolam or other sedatives are often given prior to other medications to "take the edge off." You may get this type of drug before you even leave the pre-op room. These drugs kick in within a minute and make you forget anything that happens for a period of time afterward, although the effect varies from person to person. For this reason, you may have no recollection (or only vague memories) of entering the operating room.
After you go to the operating room, you will be given oxygen to breathe and will have monitors such as a blood pressure cuff, an oxygen monitor, and EKG stickers placed.
Agents for Induction
Most commonly, your general anesthetic is induced with medicines injected into your IV. Anesthesia providers use a combination of medications that function as sedatives, pain relievers, and hypnotics for the induction (getting you to sleep) phase of general anesthesia. You may or may not remember this if you were given a sedative in the pre-op phase.
After You Are "Sleeping"
Once you are unconscious, your anesthesiologist will make sure you are getting enough oxygen and anesthesia. To do this, he or she may need to use a breathing device to help keep your airway open. There are various ways to do this, including using just an oxygen mask, an LMA (a soft rubber mask that sits inside of your mouth, just over the opening to your windpipe), or a breathing tube that slides into the windpipe between the vocal cords. The decision regarding the type of airway device is based on many factors, including any medical problems that you have and the type of surgery planned.
(Note: Although we use the word "sleeping," anesthesia is not like sleep in that you cannot be awakened until the drugs are removed from or metabolized by your body. Recent studies reiterate that it is better thought of as a controlled, reversible, coma-like state.)
Maintenance of General Anesthesia
"Maintenance" refers to the process of keeping you "asleep"/"under" for the entire surgery. Usually a combination of gas, IV hypnotics, and strong pain medication are used for this important stage.
During this phase, your anesthesiologist stays with you, carefully monitoring your vital signs and keeping you safe. Your anesthesia is adjusted throughout the operation based on what is going on in the surgery. For example, it will be "lighter" during the time that the nurse is washing the surgical area with sterilizing soap—you need less then because this is not painful or disruptive for your body. Too much anesthesia when it is not needed causes the heart rate and blood pressure to drop. When the surgeons are ready to begin, your anesthesiologist will make adjustments to make sure you have enough.
Your unconsciousness is maintained by watching your heart rate, blood pressure, and breathing rate. Medications are increased or decreased based on your specific needs during that surgery. In other words, every anesthetic is customized to the needs of the patient.
Emergence ("Waking Up")
When the surgery is over, the anesthesia gases are allowed to dissipate. Titration of pain medication continues so that you do not wake up in pain. You will move through stages of consciousness until, at last, you are awake and the breathing mask or tube is removed. Don't worry, you won't likely remember this, though. Most people don't realize they are awake until some time later in the recovery room.
Our anesthetics are much shorter-acting than those of ten years ago, but they are still going to make you feel pretty sleepy for the rest of the day after your surgery. General anesthetics have the unfortunate side effect of nausea and vomiting. If you are particularly prone to nausea (for example, from motion sickness), make sure to tell the nurses and doctors in the pre-op area. There are meds they can give you to minimize this side effect.
The pain medicines you will take after surgery have many of the same side effects. So, if you are still sleepy and experiencing nausea a couple days after your surgery, it more likely results from narcotic pain medicines than the anesthetic.
Frequently Asked Questions About General Anesthesia
How do you know I'm asleep?
Anesthesiologists monitor all of your vital signs, continuously, throughout the surgery. Increases in heart rate, breathing rate, and blood pressure all signal "light" anesthesia. Changes do not mean you are awake. Your autonomic nervous system reacts to the stressful stimuli of surgery long before you wake up. You actually move involuntarily as a reaction to the surgery while still unconscious, as well.
What is anesthesia awareness?
Anesthesia awareness is an unfortunate situation where you are not fully unconscious during the surgery. People with true anesthesia awareness later report that they heard some of what was going on in the operating room. Usually, they can't feel anything, but may be very scared. Rarely, they can feel the surgery but can't move or speak. People who have medical or surgical issues where giving deep anesthesia is dangerous are at more risk for true anesthesia awareness.
Why do you say "true" anesthesia awareness?
There are many, many cases when people think they have been awake during general anesthesia, but in fact, they are mistaken. The most common scenario involves a surgery where they had sedation anesthesia or sedation in combo with a spinal, epidural, or regional anesthetic. Those types of anesthesia do not and are not supposed to induce unconsciousness. It is absolutely normal to have memories and be at least partially awake with these types, but memories may be fuzzy due to the drugs used.
Could you use a brain monitor to prevent anesthesia awareness?
Brain monitors have not been shown to provide protection from anesthesia awareness, but don't worry, your anesthesiologist knows what to look for. Monitoring for sweating, tearing, increases in heart rate, breathing, and blood pressure are much more reliable. Brain monitors may provide other valuable information, so your anesthesiologist may use one, but not to prevent awareness.
Why do I have to have general anesthesia for this surgery?
Many types of surgery simply cannot be done with other types of anesthesia. Obvious examples are brain and heart operations, but others, such as laparoscopic abdominal surgeries, require more explanation.
When you have laparoscopic surgery, the surgeons use skinny tubes with cameras and instruments on the ends to do the operation. This causes less pain than large incisions, but in order to see into the abdominal cavity with cameras, the surgeons need to make room to operate. To do this, they inflate the abdomen with gas, usually carbon dioxide, to create a domed space in which to work. The other types of anesthesia—epidurals and spinals—that used to be used for abdominal surgery just don't cover enough of the abdomen to keep you comfortable. Also, the table is often adjusted into a "head-down" position to improve working conditions even more. The combination of an inflated belly and laying head down makes it very difficult to take deep breaths and keep your oxygen level adequate. With you asleep under general anesthesia, we can use the ventilator to make sure your lungs are fully inflated, making oxygenation easier and safer.
Why can't I eat or drink anything after midnight before my surgery?
When you go under anesthesia, it's not like normal nighttime sleep. At the point at which you become unconscious, you also lose the protective reflexes that normally keep your airway clear. For example, while awake, if something irritates your vocal cords, they would reflexively close and you would cough to clear the irritant. While unconscious with anesthesia, you may be more prone to regurgitation of stomach contents and your vocal cords and the rest of your throat can't react to prevent the material from entering your windpipe and your lungs. This can lead to a dangerous condition called aspiration pneumonitis or aspiration pneumonia. Damage to or infection of the lungs causes serious complications in some people.
So the food and water you have in your stomach could end up in your lungs. While some studies show that the usual eight hour fast before surgery may be overly cautious, and some institutions are shortening the NPO (nil per os, Latin for "nothing by mouth") interval, some will not for another reason: Surgeries sometimes cancel or get moved around. If you are lucky enough to have your surgery moved earlier in the day, but you have eaten within the NPO interval, the operating staff will not be able to move your surgery earlier. And if they move someone else up, you may end up getting delayed even later.
For information on other types of anesthesia...
- Insider's Guide to Spinal Anesthesia
Your anesthesiologist may recommend, or give you the option of, spinal anesthesia for your surgery. Learn the uses, benefits, and risks of spinal anesthesia.
- Insider's Guide to Epidural Anesthesia
Epidural anesthesia, best know for its role in alleviating labor pains, provides surgical and post-surgical pain relief for other procedures as well.