Why Does Anesthesia Awareness Occur?

Anesthesia awareness, which is also referred to as unintended awareness under general anesthesia, is a rare complication of surgery. Typically, general anesthesia ensures that you are both unconscious and paralyzed during surgery. Anesthesia awareness happens when you become aware of your surroundings during the procedure.

Approximately one to two patients per 1,000 experience some level of anesthesia awareness, ranging from being able to recall words spoken by staff to experiencing the duration of the surgery awake but paralyzed.


Types of Anesthesia Awareness

Male anesthesiologist putting an oxygen mask on a patient

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1. The sedative does not work, resulting in anesthesia awareness.

This type of anesthesia awareness is typically the most traumatic for patients. When the sedative does not work or wears off, the patient may have normal sensation and be wide awake, but the medications given to paralyze the body during surgery prevent them from alerting anyone to their problem.

Most patients who experience this type of anesthesia awareness have fleeting memories of conversation amongst the staff or the sound of machines in the OR. However, in severe cases, the patient is completely aware of their surroundings and unable to make a sound or indicate that they are awake. They may experience all of the pain, and sadly, terror, of having surgery without anesthesia.

The anesthesia provider may be completely unaware that there is a problem and have no indications that further medication is needed.

2. The paralytic and sedatives do not work, resulting in anesthesia awareness.

In this case, neither the paralytic (the medication given to paralyze) nor the sedatives are effective, and the patient is both conscious and able to move. The patient may try to remove the endotracheal tube, sit up, or try to speak.

When the patient begins to move, it is clear to the anesthesia provider that the patient isn’t fully under general anesthesia. Additional medication is given to sedate and paralyze the patient.

3. The paralytic does not work, resulting in movement during surgery.

While not strictly categorized as anesthesia awareness because the patient is unaware of the situation, he may start moving during surgery because the paralytic is not effective or the dose has worn off.

The sedative agent is working, so the patient is unaware of the movement, and an additional dose of paralytic agent can be given by the anesthesia provider to fully paralyze the patient.

4. The procedure or condition requires reduced anesthesia, resulting in more awareness than is ideal.

Some types of patients, typically those that are critically ill, having cardiac surgery or an emergency C-Section, cannot tolerate full general anesthesia. For those patients, anesthesia could cause them to become unstable. In those cases, smaller doses of anesthesia are used to prevent harm to the patient.

The result of this reduced anesthesia can mean that the patient has some awareness of the surgery. While the risk of anesthesia awareness is highest when anesthesia is intentionally reduced in this manner, it is done with the intention of saving the patient’s life and is a measured risk.


Who Is at Risk

Some types of surgery and some medical conditions can increase the risk of experiencing anesthesia awareness. The following conditions increase the chances of experiencing some level of awareness during surgery:

  • Severe trauma with blood loss and/or low blood pressure
  • Cardiac surgery
  • Cesarean section (C-section)
  • Lung disease or a condition that inhibits breathing
  • Current or past alcohol and/or drug abuse

Additional Facts About Anesthesia Awareness

Anesthesia awareness is rare and severe cases are extremely rare.

Some patients may dream during surgery and may dream of surgery. This should not be confused with anesthesia awareness.

Most patients do not experience pain, however, they may experience a feeling of pressure.

Many types of anesthesia do not render the patient completely unconscious. This is not anesthesia awareness. Anesthesia awareness only happens with general anesthesia, when the patient should be completely unaware of their surroundings.

It is normal to have awareness before the beginning of the procedure and after the procedure.

If you have a history of drug or alcohol abuse, be sure to notify your anesthesia provider, as your anesthesia dosage may need to be altered.

If you use narcotic pain medications regularly for chronic pain, notify your anesthesia provider as this may alter the necessary dosage of anesthesia.



Preventing anesthesia awareness is the responsibility of your anesthesia provider or anesthesiologist. In order for him to perform this job, it is essential that you are very candid during your pre-surgery discussion.

It is essential that your anesthesiologist knows your medical history, including any history, past or present, of drug use (prescription or illicit) and how much alcohol you drink. In addition, you will need to discuss any history you may have of difficulty with anesthesia, heart or lung issues, and any other medical problems.

In addition to a candid discussion with your anesthesiologist, if you have concerns about anesthesia awareness, you may want to request that a bispectral index (BIS) monitor be used during your case.

A BIS monitor is used to track your brain activity. A sensor is placed on your forehead and assigns a number to your level of brain activity. 0, the lowest score, indicates little to no brain activity, while 100, the highest score, would indicate that you are awake and alert.

The BIS monitor can help notify the anesthesiologist if you are more alert than you should be, even while your body is paralyzed by medication.


What to Do If You Experience Anesthesia Awareness

If you are one of the thousands of patients who experience anesthesia awareness each year, it is important that you notify the medical team providing your care as soon as you are able. It is important to document your awareness for several reasons, most importantly, if you should need another procedure, this can be prevented from happening again.

Patients who experience even minor awareness can still be disturbed by the experience and may experience nightmares and flashbacks. More severe cases can result in post-traumatic stress disorder (PTSD). Therapy is often recommended for patients who experience traumatic anesthesia awareness and should be sought as soon as the patient is physically able.

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Article Sources
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  1. American Association of Nurse Anesthetists. Anesthetic awareness fact sheet.

  2. Sandhu K, Dash H. Awareness during anaesthesia. Indian J Anaesth. 2009;53(2):148-57.

  3. Khetarpal R, Bali K, Chatrath V, Bansal D. Anesthetic considerations in the patients of chronic obstructive pulmonary disease undergoing laparoscopic surgeries. Anesth Essays Res. 2016;10(1):7-12. doi:10.4103/0259-1162.165500

  4. American Society of Anesthesiologists. Anesthesia awareness (waking up) during surgery.

Additional Reading
  • About BIS. Aspect Medical Systems.

  • Intraoperative Awareness Under General Anesthesia Pamphlet. American Society of Anesthesiologists. 2009.