Awareness may be more common than you think — Can monitoring help?

Joint Commission issues sentinel event alert on awareness

Someone in the OR makes a comment about a patient’s tattoo. In another case, a catheter doesn’t get connected, and urine ends up on the OR floor. Someone gets mad about the mess and starts yelling. Do these situations sound like a bad day in the OR? Now imagine the patient wakes up in recovery and tells you she heard what your staff said, but she was paralyzed and unable to speak.

Awareness during anesthesia may not be as isolated as once thought. These are just two cases of awareness uncovered in a recently published study that determined about 100 patients per workday in the United States experience awareness, or 26,000 cases per year.1 The Joint Commission on the Accreditation of Healthcare Organizations, which just released a sentinel event alert on awareness, points to other awareness studies2,3 and that as many as 40,000 patients may experience awareness each year. (See Joint Commission tips.)

In addition to patients who heard conversations in the OR, other patients reported feeling as if they couldn’t breathe. Some felt their bodies being cut. One thought he was going to die and decided he’d just give up.

"I would most like people to know the incident of awareness during anesthesia in the United States is generally underestimated," says Peter S. Sebel, MB BS, PhD, MBA, a professor of anesthesiology at Emory University School of Medicine in Atlanta. "It is a recognized complication, and we should look at ways of reducing it."

Sebel’s study of 19,575 patients is the largest study of awareness ever conducted. Sebel is a paid consultant for Aspect Medical Systems in Newton, MA. While some studies have found no difference in awareness between outpatients and inpatients, one study found a high incidence of awareness among 56 elective surgical patients who were instructed to squeeze the observer’s hand.

Of the 37 patients (66%) with an unequivocal response to command, which was defined by the authors as awareness, nine (25%) reported conscious recall after recovery. The Bispectral Index (BIS) was a highly significant predictor of awareness, the authors reported.4

The issue of awareness has gotten much national attention. The Joint Commission has issued a sentinel event alert on that topic. (For information on sentinel event alerts, go to The most recent sentinel event alert issue is listed under "Latest Newsletters.")

Some awareness cases have received widespread press coverage, and patients report that awareness is a significant concern to them.5

"Of major concern are the subset of these patients who develop a post-traumatic stress disorder [PTSD]," says Donald M. Mathews, MD, associate chairman for academic affairs in the department of anesthesiology at St. Vincent’s Hospital Manhattan and assistant professor of anesthesiology at New York Medical College in Valhalla, NY. The only data that speak to the issue of PTSD after awareness are from Scandinavia,6 which suggest that about 20% to perhaps 40% of patients go on to develop PTSD, Mathews says. "I personally think that we are looking at a significant issue here," he says.

Some anesthetists aren’t concerned about awareness because it’s never happened to them before, Sebel acknowledges. "My answer to that is, It’s never happened to you because you haven’t looked for it,’" he says.

Also, patients often don’t tell their anesthetist when they’ve been aware, says Sebel, pointing to a study that indicated 35% of patients who said they had experienced awareness never told their anesthesiologists.7 "They’re frightened," he says. "They think anesthesiologists will tell them they’re crazy."

Anesthetists don’t consider awareness as their biggest risk for complications, says Sandra Ouellette, CRNA, MED, FAAN, director of the Nurse Anesthesia Program at Wake Forest University Baptist Medical Center/The University of North Carolina — Greensboro in Winston-Salem and past president of the American Association of Nurse Anesthetists in Park Ridge, IL.

Also change comes hard to many medical professionals says Ouellette, who points to initial resistance to pulse oximeters in the 1980s.

The controversial question is should "depth of consciousness" monitors, also known as "depth of hypnosis monitors" or "brain activity" monitors, be used, Mathews says. "In my opinion, yes," he says emphatically, pointing to studies published in the past year that show monitoring with the BIS monitor decreases the incidence of awareness in high-risk surgery8 and during routine care.9

According to the Joint Commission, monitors — including the BIS — "may have a role in preventing and detecting anesthesia awareness in patients with the highest risk, thereby ameliorating the impact of anesthesia awareness."10

Others are supportive of the monitors, but for other reasons. "Sufficient studies have shown that these monitors are very useful in titrating the depth of anesthesia, to improve rate of quality of recovery, reduce the need for postoperative mechanical ventilation, and even allow the use of fast-track anesthesia," says Rebecca S. Twersky, MD, professor of anesthesiology at the State University of New York Downstate Medical Center and medical director at the Ambulatory Surgery Unit — Long Island College Hospital, both in Brooklyn.

The monitors have enjoyed some popularity. Aspect says its BIS monitors are available in about 30% of hospital operating rooms in the United States.

The monitors would be particularly helpful in office-based surgery, Twersky says, because there often is not a formal recovery area, and patients often are expected to walk away from the OR table. "However, these uses are for titration of anesthesia, NOT because they are preventing recall or intraoperative anesthesia," she says. Patients who are well anesthetized do not remember, Twersky maintains. "You don’t need a BIS, PSA, or other monitor to help you anesthetize a patient well," she adds.

The question really is about the frequency of intraoperative recall and whether these monitors can indeed prevent the occurrence, Twersky says.

"Thus far, the literature is not convincing enough that the monitors are foolproof," she says. "E.g., under intravenous general anesthesia with opioids, these monitors are not as sensitive to depth of anesthesia as they are with inhalational anesthesia."

There have been reports of anesthetists having digital readouts that would indicate patients are unconscious, when in fact, they end up being reported cases of awareness, Ouellette explains. "They’re not 100% assuring that you will prevent it by using a monitor," she says.

For this reason, one disadvantage of the monitors is that they may give anesthesia providers a false sense of security, Ouellette says. Cost is another factor, she notes.

According to Aspect, the list price for the BIS machine is about $9,500, and the list price for the single-use sensor is $17.50 each.

Whether monitors should be used for all cases or just risk cases is very controversial, Ouellette says. "My personal opinion is, if the technology is available, why not use it in all cases?" she notes. Consider how you would react if you had the technology available, opted not to use it, and a patient experienced awareness.

Monitors should be used in "all cases with general anesthesia, especially with muscle relaxant use," Mathews maintains. All patients are at risk for awareness, he explains.

The American Society of Anesthesiologists in Park Ridge, IL, is developing a white paper and guidelines related to the issue of awareness that should be available in October 2005, sources say. At this point, "the ASA has not endorsed this monitor as a basic anesthesia monitor or a standard of care, and further investigation is needed," adds Twersky.

"In using this [monitor], it’s another piece of data that you have that may guide your anesthetic management of the case," Ouellette sums up.


1. Sebel PS, Bowdle TA, Ghoneim MM. The incidence of awareness during anesthesia: A multicenter United States study. Anesth Analg 2004; 99:833-839.

2. Lennmarken C, Sandin R. Neuromonitoring for awareness during surgery. Lancet 2004; 363:1,747-1, 748.

3. Osterman JE, Hopper J, et al. Awareness under anesthesia and the development of post-traumatic stress disorder. General Hospital Psychiatry 2001; 23:198-204.

4. Kerssens C, Klein J, Bonke B. Awareness: Monitoring versus remembering what happened. Anesthesiology 2003; 99:570-575.

5. Myles PS, Williams DL, Hendrata M, et al. Patient satisfaction after anaesthesia and surgery: Results of a prospective survey of 10,811 patients. Br J Anaesth 2000; 84:6-10.

6. Lennmarken C, Bildfors K. Victims of awareness. Acta Anaesthesiol Sand 2002; 46:229-231.

7. Moerman N, Bonke B, Oosting J. Awareness and recall during general anesthesia. Anesthesiology 1993; 79:454-64.

8. Myles PS, Leslie K, J McNeil J, et al. Bispectral index monitoring to prevent awareness during anaesthesia: The B-Aware randomized controlled trial. The Lancet 2004; 262: 1,757-1,763.

9. Ekman A, Lindholm M-L, Lennmarken C, et al. Reduction in the incidence of awareness using BIS monitoring. Acta Anaesth Scand 2004; 48:20-26.

10. Joint Commission on Accreditation of Healthcare Organizations. Preventing, and managing the impact of, anesthesia awareness. Sentinel Event Alert Oct. 6, 2004; 32:2-3.


For more on monitoring for anesthesia, contact:

  • Donald M. Mathews, MD, Associate Chairman for Academic Affairs, Department of Anesthesiology, St. Vincent’s Hospital Manhattan, Assistant Professor of Anesthesiology, New York Medical College, Valhalla. E-mail:
  • Sandra Ouellette, CRNA, MED, FAAN, Winston-Salem, NC. Phone: (336) 768-5107. E-mail:

For more on the BIS monitoring system, contact:

  • Aspect Medical Systems, 141 Needham St., Newton, MA 02464 . Phone: (617) 559-7000. Fax: (617) 559-7400. Web: