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Anesthesia Awareness: Awake and Aware

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Author:    Patricia Hartley (RNC, MSN)


Like being entombed in a corpse is how one patient described being aware of some portion of her five-hour ordeal for enucleation/corneal implant surgery nearly seven years ago. Because she cannot lie supine, she sleeps two- to three-hour intervals in a recliner. She often awakens with cuts and scratches on her face because she unconsciously digs at her face. She remembers hearing one surgeon telling the other to “cut deeper” and “pull harder”, feeling intense tugging on her eye and a blinding white surgical light. This patient felt painful burning sensations scorching through her body after the injection of a paralytic medication. The most horrifying experience was the feeling of being consciously entombed on the operating table with no means of escape.

Another patient says that the first thing he heard when he awoke in the operating room during open heart surgery was the insistent whine of a bone saw cleaving his sternum. As doctors began discussing his badly damaged heart, he wondered whether he was eavesdropping on his own death. Seconds later, he felt jolts of searing pain as the doctors shocked his stopped heart. He remembers screaming that it was killing him and he felt like he was being buried alive. He regularly relives his ordeal in nightmares so vivid that he has cracked several teeth while grinding them in his sleep.

These patients suffer from post traumatic stress disorder (PTSD) after becoming awake and aware during surgery and not being able to rid their minds of the memories. They are victims of an uncommonly large, unrecognized, and often psychologically devastating experience known as anesthesia awareness, or intraoperative awareness. Every year an estimated 20,000 to 40,000 of the 21 million patients who receive general anesthesia wake up during surgery because they are under-anesthetized, usually by mistake or because doctors fear too high a dose of anesthesia could be dangerous. Half of these patients can hear or feel what is going on but are unable to communicate what is happening to them because they have been temporarily paralyzed. Studies have shown that nearly 30 percent feel pain. As a result of the experience, about 50 percent of awareness victims develop serious psychological problems including PTSD. Physicians and nurses must balance the psychological risks of anesthesia awareness against the physiological risks of excessive anesthesia.

Memory is not a single entity. Current classification distinguishes between two types: explicit or conscious memory and implicit, or unconscious, memory. Implicit memory refers to changes in performance or behavior that are produced by previous experiences, but without any conscious recollection of those experiences. Explicit memory, by contrast, refers to the conscious recollections of previous experiences. Explicit memory is equivalent to remembering (e.g., can you remember what you did last Monday evening?). There are two distinct types of anesthesia awareness or intraoperative awareness that can occur under general anesthesia: explicit recall and implicit recall. In the case of anesthetized patients, explicit memory refers to awareness during anesthesia with memories ranging from virtually every word and action of the operating room personnel to only a few selected recollections. Explicit recall is responsible for most of the traumatic and horrific incidents of awareness. Implicit recall emerges indirectly through painful, often inexplicable, psychological difficulties that appear following surgery. Anesthesia awareness, also called unintended intraoperative awareness, occurs under general anesthesia when a patient becomes cognizant of some or all events during surgery or a procedure, and has direct recall of those events. Because of the routine use of neuromuscular blocking agents (also called paralytics) during general anesthesia, the patient is often unable to communicate with the surgical team. Although patients are unable to communicate their level of awareness because of the induced paralysis or intubation, they are aware of their surroundings.

General anesthesia is an extremely safe process that allows surgeons to perform complex and necessary procedures that benefit millions of patients. Yet, one or two of every 1,000 patients receiving general anesthesia experience this frightening phenomenon known as anesthesia awareness or intraoperative awareness. These patients awaken from anesthesia during the procedure and are mentally aware of what is happening to them, but physically unable to move or alert their caregivers. Almost half of the patients experience the sensation of being unable to breathe and one quarter felt pain from the surgical procedure. While the overall frequency of anesthesia is low (0.1 - 0.2 percent) there are approximately 21 million surgeries performed under general anesthesia each year. That translates to an average of 40 to 70 cases per day.

The incidence of awareness during anesthesia and surgery is best estimated by formally interviewing patients postoperatively. Patients, particularly those who were not unduly disturbed by their experiences, may not voluntarily report them without being asked directly. Some patients also may not recall events shortly after surgery but may recall them one to two weeks after surgery. A recent study found that recall of awareness is greater seven days after surgery than it is 24 hours afterward. Surgeons are not tuned into anesthesia awareness. Unlike anesthesiologist or nurse anesthetists, surgeons typically see patients for postoperative appointments. It is also possible that some patients may need a detailed and extensive interview to jog their memories for the intraoperative experience. Anesthesia awareness is generally under recognized and under treated. That is why the Joint Commission on Accreditation on Healthcare Organization (JCAHO) has issued a Sentinel Event Alert to draw attention to the problem of anesthesia awareness. The JCAHO intent is to provide practical advice to healthcare organization leaders and healthcare professionals to help prevent the occurrence of anesthesia awareness, or when it occurs, to ensure that patient’s needs are appropriately met.


There is no doubt that pain during surgery is the most distressing feature of awareness but feelings of helplessness, anxiety, panic, and impending death can also occur when the patient is paralyzed. The majority of patients who experience awareness tend to suffer some temporary sleep disturbances, nightmares, anxiety, and/or flashbacks which subside eventually. Yet there may remain a fear that awareness can happen again if they require anesthesia in the future. Some patients are so traumatized that they avoid doctors entirely and vow never to undergo surgery again. Others suffer from flashbacks and panic attacks triggered by the smell of rubbing alcohol, the sound of metal on metal, which reminds them of the surgical instruments, or the sight of surgical scrubs on a TV show. Sometimes chronic PTSD sets in, marked by repetitive nightmares, anxiety, and irritability. It is not evident why PTSD develops in some patients and not in others. Potential factors may include patient personality, predisposition to mental disease, and emotional response to illness.

Psychiatrists say that when doctors minimize or deny intraoperative awareness, patients tend to suffer more severe psychological problems. Numerous studies of malpractice have found that doctors who stonewall patients after a serious injury are more likely to be sued than those who are forthcoming. The unexpected awareness is traumatic enough, but when the patient tells the doctor what happened and he says it couldn’t have, that becomes a secondary trauma. Dismissive reactions are not uncommon. Anesthesiology is a specialty that attracts doctors who don’t tend to think in psychological terms or spend much time with patients. The apparent lack of concern reflects part of the culture of medicine to minimize the suffering that people go through.

There are consequences for practitioners and facilities as well. Anesthesiologists have been reluctant to talk to patients about intraoperative awareness, which a recent study characterized as second only to death as the dreaded complication among anesthesiologists. A 1999 analysis of 4,183 closed malpractice claims from the database of the American Society of Anesthesiologists showed that 1.9 percent were awareness claims payments ranged from $1,000 to $23.2 million. The median payments for patients inadvertently paralyzed while awake and for patients who experienced recall during general anesthesia were $10,250 and $105,000, respectively. There is concern that the JCAHO alert could trigger more malpractice suits against anesthesiologists. Plaintiffs’ attorneys claim that, in the past, people who awoke during surgery rarely sued because they couldn’t prove it and doctors ignored them. Now these patients have ammunition in the JCAHO alert as well as increased publicity surrounding the issue and the recent availability of a new monitoring device that measures brain waves and tells when a person is regaining consciousness. Patients want the device used; however, many physicians believe it is unreliable.


Anesthesia awareness has multiple causes. Sometimes it is the result of defective equipment or physician error, such as failure to accurately calculate the dose of a drug or to check whether a machine is working properly before surgery starts. Other cases occur when anesthesia is lightened too early at the end of a case to facilitate operating room turnover, or when an intentionally light dose is given to a cardiac or trauma patient for fear that too much anesthetic could be dangerous or even fatal.

General anesthesia typically consists of three kinds of drugs: a paralytic to prevent movement, a hypnotic gas or intravenous drug that renders the patient unconscious and unable to remember what happened or to feel pain signals, and a pain killer. Doses are calculated based on a variety of factors, among them body weight, body fat, and medical history. Alcohol, obesity, and certain drugs can affect how much anesthesia is necessary. As with all medications, people metabolize anesthesia at different rates. It is the job of the anesthesiologist or nurse anesthetist to continuously monitor the patient’s condition through vital signs, including blood pressure, respirations, and heart rate to ensure the patient is unconscious, stable, and pain free. However, physicians say these signs are imperfect markers because beta blockers, along with other drugs, can depress blood pressure or affect heart rate. A patient who wakes up during surgery might not show a jump in either sign. Some physicians compare the situation to flying through fog; a pilot relies on instruments and expertise, but can’t see clearly. Anesthesiologists think they can measure the depth of anesthesia, but there are times when this is not true. It is difficult to measure in especially light anesthesia, such as cardiac cases or trauma with lots of blood loss.

Five factors that have been significantly associated with recall under general anesthesia claims:

  1. female gender
  2. gynecological/obstetrical procedures
  3. use of opioids
  4. use of muscle relaxants
  5. lack of use of a volatile anesthetic agent

Awareness is associated with one of three situations:

  1. Light anesthesia – for certain operations, such as cesarean section, hypovolemic patients, and those with minimal cardiac reserve the patient is provided light anesthesia. Consciousness and recall occurs because judgments of depth of anesthesia are not precise. Muscle relaxants also lead to the problem in the motionless patient. This is probably the most common cause of awareness. Because anesthetic concentrations that block awareness are less than those that prevent motor responses to pain, an inadequately anesthetized, but paralyzed patient usually communicates wakefulness by movement. Deepening the anesthetic at this stage usually prevents awareness.
  2. Increase anesthetic requirement of some patients that may be more resistant to the effects of anesthetics than others. Younger age, tobacco smoking, and long term use of certain drugs (alcohol, opiates, or amphetamines) may increase the anesthetic doses needed to produce unconsciousness. Even high doses of vitamin C may interfere. Many surgeons recommend high doses of vitamin C to aid the healing process, but these should be withheld until after surgery. A high level of vitamin C is so detoxifying that it can complicate the anesthesia process.
  3. Machine malfunction or misuse resulting in an inadequate delivery of anesthesia may be caused by an empty vaporizer or IV pump malfunction or disconnection of its delivery tubing.


Prevention of recall of events during anesthesia should be feasible in most cases. Monitoring levels of anesthesia during surgery is challenging. Despite a variety of available monitoring methods, awareness is difficult to recognize while it is occurring. Typical indicators of physiologic and motor response, such as high blood pressure, fast heart rate, movement, or hemodynamic changes are often masked by the use of the paralytic agents to achieve necessary muscle relaxation during the procedure as well as the concurrent administration of other drugs necessary to the patient’s management, such as beta-blockers or calcium channel blockers. The new emerging brain wave monitoring devices are promising, but not established, protocol. They are less affected by the drugs typically used during general anesthesia. These devices measure brain activity rather than physiological responses. The following guidelines from the American Society of Anesthesiologists and the American Association of Nurse Anesthetists offer specific suggestions for reducing the risk of awareness:

  1. Educate clinical staff about anesthesia awareness and how to manage patients who have experienced awareness.
  2. Identify patients at proportionately higher risk for an awareness experience and discuss the potential for anesthesia awareness before surgery.
  3. Effectively apply available anesthesia monitoring techniques and ensure the timely maintenance of anesthesia equipment.
  4. Provide appropriate postoperative follow-up to all patients who have undergone general anesthesia, including children.
  5. Identify, manage, and refer patients who have experienced awareness, PTSD, or mental distress to the appropriate counseling or support services.

The American Society of Anesthesiologists has been educating its members about awareness for years. Although anesthesia awareness is rare, even one preventable case is one too many. In those very rare instances of awareness under general anesthesia, patients deserve the support of their entire healthcare team. It isn’t safe in many instances, such as trauma, cardiac surgery, and emergency cesarean sections for the patient or the baby to receive the deepest level of anesthesia which would prevent awareness. Compassion of the physician is essential in dealing with the situation. There is a potential for awareness to be sensationalized. Patients can become unduly frightened during what is already a very emotional time for them. Anesthesiologists have devoted their lives to keeping patients as safe and as pain free as possible. While a patient is under general anesthesia anesthesiologists are the ones who vigilantly monitor their body systems. Surgery is not easy for anyone. When patients come to the hospital for surgery, or in a critical situation, they feel very, very vulnerable. This is an area of their lives that they feel they cannot control so they deserve to know about the steps that are being taken every day to ensure their experience is the best that it can be.


If a patient complains of awareness, a detailed account of the experience should be obtained. Although there have been cases of fraudulent claims and mistaken recall of events during the emergence from anesthesia, most claims are genuine and credibility can be established easily. The patient should be assured that the anesthesiologist believes their account and sympathizes with their suffering. Denial of the authenticity of the patient’s experience may adversely influence the patient’s psychologic recovery and may turn the patient toward litigation. Some explanation of what happened and its reasons should be given; e.g., necessity to administer light anesthesia in the presence of significant cardiovascular instability.

The patient should be reassured about nonrepetition of the same mishap with future anesthesia because the details will be in the patient’s record and will guide the anesthesiologist managing subsequent anesthesia. An apology should be given; it is possible to apologize with out admitting liability. The patient should also be offered psychologic or psychiatric support. The details of the interview should be recorded in the patient’s chart and the surgeon, the patient’s nurse, and the hospital attorney or physician’s insurer should be notified. A healthcare facility risk management staff member should also be made aware of the event. Subsequently, the patient should be visited daily during the hospital stay to look for and treat psychologic sequelae; e.g., sleep disturbances and daytime anxiety, After the patient is discharged, frequent contacts by telephone should be made until the patient is judged to be fully recovered. Referral to a psychiatrist or psychologist should not be delayed; there is anecdotal evidence that early counseling may reduce the incidence of PTDS.

Facility policies and procedures should be developed to address care of patients who experience anesthesia awareness. This policy should include staff member education to recognize and manage patients who experience anesthesia awareness. The organizational quality improvement process should include reviewing anesthesia awareness incidents. Brain activity monitoring devices should be considered and evaluated for purchase by the facility. This consideration should be documented for accrediting agency review.

Nursing Responsibilities

Perioperative nurses can assist in preventing awareness in patients under anesthesia by educating themselves about the issue, implementing appropriate interventions throughout the perioperative period, and helping to increase other staff members’ sensitivity to the issue. The nurse interviewing the patient during the preoperative phase needs to assess the patient for previous anesthesia awareness. If identified, the nurse must immediately notify the anesthesia provider and those directly involved with the patient’s intraoperative phase.

Intraoperatively there should be minimal conversation and all conversation should be case related. No inappropriate comments should be made as the patient may recall this information. The intraoperative nurse also needs to provide the patient with constant reassurance and support to help decrease anxiety and promote a nurturing environment.

Postoperatively, if the patient recalls specifics of the surgery, the nurse needs to notify the anesthesia provider as soon as possible. Patient support during the immediate postoperative period is critical. The nurse should take time to listen and believe the patient’s statements. If the anesthesia provider is not present, the nurse should attempt to explain what has happened, offer psychological support, and apologize for the situation. During the discharge process, education should include the patient’s need to discuss the situation with all future anesthesia providers.

Future Management Strategies

To overcome the limitations of current methods to detect anesthesia awareness there are new methods to assess level-of-consciousness that are less affected by the drugs used during general anesthesia. These devices measure brain activity rather than physiological responses. These electroencephalography (EEG) devices (also called level-of-consciousness, sedation-level and anesthesia-depth monitors) include the Bispectral Index Monitoring - BIS™, spectral edge frequency (SEF), and median frequency (MF) monitors.

The best way to detect whether a patient is sufficiently anesthetized is by using a specialized EEG machine to monitor brain waves. In a few years such monitoring will become the standard of practice. The Food and Drug Administration, who approved the BIS in 1996, recently authorized Aspect Medical Systems to market it for awareness reduction. Two prospective studies involving more than 7,000 patients found that the BIS reduced the risk of anesthesia awareness by about 80 percent.

Many nurses and anesthesiologists have resisted using the BIS and similar monitors because the devices have not been tested by their professional societies. Many say they consider their clinical judgment (monitoring vital signs) to be a better way of gauging whether a patient is awake. Monitoring can help guide anesthesia administration to reduce incidence of awareness with recall. Studies have been published in The Lancet and the Acta Anaesthesiologica Scandinavica that demonstrate that consciousness monitoring with the Aspect BIS monitoring system reduced the risk of awareness by approximately 80 percent when compared to standard practice.

5.The BIS monitor uses a sensor placed on the patient’s forehead which translates information from the electroencephalogram (EEG) into a single number that represents each patient’s level of consciousness. The number – the BIS value – ranges from 100 (indicating an awake patient) to zero (indicating the absence of brain activity). Using the BIS value to guide administration of anesthesia in conjunction with other vital signs allows clinicians to make better informed decisions to achieve optimal anesthesia. These devices may have a role in preventing anesthesia awareness in patients with the highest risk, thereby ameliorating the impact of anesthesia awareness. A body of evidence has not yet accumulated to definitely define the role of these devices in detecting and preventing anesthesia awareness.


The waking of patients during general anesthesia is an uncommon complication, though alarming to patients and anesthesiologists. Considering that approximately 20 million general anesthetics are administered each year in the United States, the incidence of one case in 500 corresponds to 40,000 cases of awareness annually.

Awareness appears to be dose related and the risk is greatest when muscle relaxants are used. Its most feared consequence is PTSD. Management of a case of awareness should be precise, detailed, compassionate, and documented.

Measures to prevent awareness include avoidance of overly light anesthesia, gaining more knowledge about anesthetic requirements of patients, and development of methods to detect consciousness during anesthesia. The American Association of Nurse Anesthetists and the American Society of Anesthesiologists are working with JCAHO to address the adequacy of current monitoring practices regarding anesthesia levels, including those that involve little or not technological support.


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Boodman,Sandra G., Wake-Up Call, Washington Post, Nov. 23,2004 p.HE01.

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Ekman, A., Lindholm, M.L., Lennmarken, C., Sandin, R., Reduction in the Incidence of Awareness Using BIS Monitoring. Acta Anaesthesiologica Scandinavica 2004; 48 (1):
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JCAHO Joint Commission Issues Alert on Patient Awareness Under Anesthesia

Myles, P., Leslie, K., McNeil, J., Forbes, A., Chan MTV., Bispectral Index Monitoring to Prevent Awareness During Anesthesia: The B-Aware Randomised Controlled Trial. The Lancet 2004; 363: 1757 – 63.

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Sentinel Event Alert, Preventing, and managing the impact of, anesthesia awareness, Issue 32, October 6, 2004.