Q: I'm undergoing a major surgical procedure in the near future that will require general anesthesia, and recently, I've been hearing a lot about anesthesia awareness. What exactly is this, and what are the chances of it happening to me?

A: General anesthesia is an extremely safe, necessary, and reliable technique that allows surgeons to perform many complex surgeries. Anesthesia awareness (or "unintended intra-operative awareness") is a rare phenomenon that occurs in 0.1 to 0.2 percent of patients during general anesthesia, when a patient has not had enough analgesic to prevent consciousness. 

While the majority (about 72 percent) of these patients experience no pain, they may become cognizant of some or all events during surgery or flashbacks of the procedure. Although patients who either dream or remember some things from just before or after their surgery may think they have experienced awareness, these types of memories do not represent actual anesthesia awareness.

Anesthesia awareness can happen for a number of reasons but occurs most frequently during surgical procedures that require the level of anesthesia to be kept lighter than usual for the safety of the patient and thus might not be deep enough to prevent anesthesia awareness. For this reason, anesthesia awareness occurs most often in cardiac anesthesia, severe trauma, and obstetric surgeries.

Other factors that can increase the incidence of anesthesia awareness are the use of muscle relaxants, failure or improper maintenance of anesthesia equipment, lapse of vigilance on the part of the anesthesiologist, or increased resistance to anesthetics by some patients.

Although anesthesiologists are constantly monitoring for signs that the patient may be "too light" on anesthesia, many indicators, such as movement and increased blood pressure and heart rate, can be masked by muscle relaxants, which may be necessary for some surgeries, or other drugs like beta-blockers and calcium channel blockers that are taken by many patients for high blood pressure.

To decrease the risk of anesthesia awareness occurring during your procedure, anesthesiologists can take a number of precautions including, but not limited to, the following:

  • Pre-medicating the patient with amnesia-producing drugs like midazolam or diazepam;
  • Giving a larger dose to put the patient to sleep before placing a breathing tube;
  • Avoiding muscle relaxants unless absolutely necessary;
  • Properly maintaining anesthesia equipment and checking anesthesia machine before administering anesthesia
  • Identifying high-risk patients, discussing issues with them, and possibly adjusting the anesthesia plan; and
  • Thoroughly educating anesthesia personnel about anesthesia awareness.

As a patient, you also play a critical in helping to reduce your risk.  For this reason, a highly trained anesthesia professional should be involved in your surgical procedure, as no technology or monitor can replace this expertise. You should speak with your anesthesia professional before surgery to discuss all of your concerns, including the remote possibility of awareness.

Remember that anesthesia awareness is extremely rare, and this remote possibility should not deter you from having needed surgery. Your anesthesia professional can help you stay informed and comfortable about your upcoming anesthesia and ensure that you receive best possible care in the operating room.


Drag Vujic, M.D., a board-certified diplomat of the American Board of Anesthesiology, is currently the chief of the anesthesiology department at Hackettstown Regional Medical Center. He is a diplomat of the National Board of Examiners and a member of both the American Society of Anesthesiologists and the New Jersey State Society Anesthesiologists. He earned his M.D. at Thomas Jefferson Medical School in Philadelphia and completed his residency as well as a fellowship in pain management and advanced clinical anesthesia at University of Medicine and Dentistry, New Jersey.