Is it possible to be aware under anesthesia?
Although it is possible to have awareness of a surgery while under general anesthesia, this is an exceedingly rare phenomenon. The frequency of this occurring is about 1-2 per one thousand surgeries, which is much rarer than about 40 years ago when it was 1-2 per one hundred surgeries. Improvements in anesthesia care led to this improvement.
There are some important details to know about awareness under anesthesia. Being aware of things right before going to sleep for surgery or while waking up when the surgery is over is not awareness under anesthesia. Some people dream while they are under anesthesia; dreaming is not the same as awareness. When awareness does occur, it can happen in a variety of ways, many of which are not painful or stressful; such as vague recollections, feelings of pressure, or hearing something specific during surgery. In certain instances, the experience can be disturbing and some patients benefit from counseling after surgery.
Although no one can predict who will have awareness, there are some things that increase the chance of it happening. Certain surgeries are higher risk. For example, an emergency surgery where patients are so critically ill that administering normal amounts of anesthesia can negatively affect the blood pressure and harm the patient. Heavy alcohol use and drug use (especially illegal drugs, but also some legal drugs) put patients at higher risk. Be sure to tell your anesthesia provider if you have had awareness under anesthesia in the past, and please discuss openly use of alcohol, recreational drugs, and prescription sedatives/narcotics.
Here is a link to more information from the American Society of Anesthesiologists:
Awareness and Anesthesia