What is general anesthesia?

Stuart A. Linder, MD
Plastic Surgery
General anesthesia can be defined with patients completely put under anesthesia, normally with the airway protected. In my practice, our anesthesiologists either use laryngeal mask airways (less invasive), or endotracheal tubes in more risky patients, including patients with reflux disease. The specific mechanism of action of general anesthetics is not completely delineated. In fact, most anesthesiologists will tell you they do not know the absolute specific mechanisms of the anesthetics on the brain. General anesthesia, in general, require "an empty stomach" and therefore our patients are required  not to eat after midnight before surgery in order to prevent aspiration of gastric contents into the lungs. General anesthesia should be performed by either board-certified anesthesiologists or certified registered nurse anesthetists. I prefer board-certified anesthesiologists with many years of experience and training. For anesthesia types of emergency situation, these doctors have the capability, experience, and judgment to take care of the probem.

During general anesthesia, patients are "put under," which means they're totally unconscious and immobilized. You will"go to sleep" and won't feel, sense or remember anything that happened after the drugs began to work.

It is not completely clear how general anesthetics work. The accepted theory is that they affect the brain stem reticular activating system (explaining the unconsciousness), the spinal cord (why you end up immobile), and the cerebral cortex (resulting in changes in electrical activity on an electroencephalogram).

Complex, major surgeries that require a long period of time typically require general anesthesia. Patients might be under for a few hours during knee replacement, or as long as six hours for something more complicated, like heart bypass surgery.

People with certain conditions might require special care under anesthesia – for example, a patient with low blood pressure might need medication such as ephedrine. Patients who are drug users or heavy drinkers also tend to react differently to anesthesia. The anesthesiologist will tell you not to eat for several hours before surgery. Under general anesthesia, it's possible for someone to aspirate, or breathe in, the stomach's contents.

While under general anesthesia, you'll wear a breathing mask or breathing tube. The muscles become too relaxed to keep airways open. Several things are monitored continuously – including heart rate, blood pressure, respiratory rate, pulse oximetry (oxygen level in the blood), temperature, carbon dioxide exhalation levels, brain activity and the concentration of the anesthetic.

The four stages of general anesthesia:

  • During induction, the first stage, a patient is given medication and may start to feel the effects but hasn't yet fallen unconscious.
  • Next, during excitement, patients may twitch and have irregular heart rates or breathing patterns. In this stage, patients don't remember this happening because they're unconscious. This is a very short stage and rapidly progresses to stage three.
  • At stage three, breathing becomes regular, the muscles relax and the patient is considered to be anesthetized fully.
  • A fourth stage is not considered a standard stage of anesthesia -- when a patient receives an overdose of drugs. This can result in breathing stoppage or heart stoppage, brain damage or death. Swift action is necessary.

Continue Learning about Anesthesia for Surgical Procedures

Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.