Anesthesia Awareness Registry
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Medical Journal Articles on Awareness during General Anesthesia

Frequency of Anesthesia Awareness

  1. Sandin RH, Enlund G, Samuelsson P, Lennmarken C. Awareness during anaesthesia: A prospective case study. Lancet 355: 707-11, 2000. {Abstract}
    1. Summary: In this study of 11,785 patients awareness occurred in 0.15% or (1 in 655). This study found that multiple interviews after the anesthetic may be necessary to discover that awareness occurred. It was also discovered that awareness occurred with greater frequency in patients where muscle relaxant (paralyzing) medications were used as part of the anesthetic.
  2. Sebel PS, Bowdle TA, Ghoneim MM, et al. The incidence of awareness during anesthesia: A multicenter United States study. Anesth Analg 99: 833-9, 2004. {Abstract}
    1. Summary: This was the first large prospective study examining the incidence of awareness during anesthesia in the United States. Out of nearly 20,000 patients 25 patients experienced awareness, that is one person out of 783 or 0.13%.
  3. Pollard RJ, Coyle JP, Gilbert RL, Beck JE. Intraoperative awareness in a regional medical system: A review of 3 years’ data. Anesthesiology 106: 269-74, 2007. {Abstract}
    1. Summary: In this study 1 out of 14,560 (.007%) patients experienced awareness, this is approximately 20 times less than the incidence from other major studies. One possible explanation for this different finding was that patients were not asked as directly about awareness as they were in other studies. Other studies have found that patients may not choose to discuss or recall that they were aware unless they are asked directly about it on more than one occasion.

Etiology / Causes

  1. Ghoneim MM, Block RI. Learning and memory during general anesthesia: An update. Anesthesiology 87: 387-410, 1997. {Abstract}
    1. Summary: The evidence for learning and implicit memory during anesthesia is reviewed in this article. Studies examining positive statements during anesthesia made to enhance recovery and the possibility that patients are stressed by occurrences during anesthesia that are not explicitly remembered are reviewed.
  2. Ranta SO-V, Laurila R, Saario J, Ali-Melkkila R, Hynynen M. Awareness with recall during general anesthesia: Incident and Risk Factors. Anesth Analg 86: 1084-9, 1998. {Abstract}
    1. Summary: This study evaluated 2612 patients undergoing general anesthesia over the course of one year in a major hospital. Awareness occurred in 0.4% (1 in 250). When patients with awareness were compared to other patients without, the researchers found that significantly lower doses of anesthetic medications were used in patients with awareness.
  3. Domino K, Posner KL, Caplan RA, Cheney FW. Awareness during Anesthesia: A closed claims analysis. Anesthesiology 90: 1053-1061, 1999. {Abstract}
    1. Summary: The uncommon occurrence of awareness makes it difficult to study to understand what can be done to prevent it. The authors of this study used information gathered during awareness malpractice claims to help understand what factors and anesthetic problems are associated with awareness. The authors recognized that awareness associated with malpractice claims would likely be more severe than awareness in patients found through other methods of study.
  4. Ghoneim MM. Awareness during anesthesia. Anesthesiology 92: 597-602, 2000. {Abstract}
    1. Summary: In this short review article, the author discusses the differences between explicit and implicit memory during anesthesia. Implicit memory is the idea that even though a patient may not remember details of their operation, the experience may cause post-operative changes in behavior. Some of the causes of awareness highlighted in this review include light anesthesia as required by the patient’s health, unrecognized high anesthetic requirement in some patients, and anesthetic machine malfunction or misuse resulting in inadequate delivery of anesthetic.
  5. Errando CL, Sigl JC, Robles M., Calabuig E, Garcia J, Arocas F, Higueras R, Rosario E del, Lopez D, Perio CM, Soriano JL, Chaves S, Gil F, Garcia-Aguado R. Awareness with recall during general anaesthesia: a prospective observational evaluation of 4001 patients. British Journal of Anaesthesia 101 (2): 178-85, 2008. {Abstract}
    1. Summary: The authors interviewed patients who underwent general anesthesia for surgery three different times for awareness with recall. The incidence for awareness was 39 out of 3921 patients (1.0%). They also reported that a majority of patients (over 50%) dreamt during the surgery.

Monitoring

  1. Ekman A, Lindholm M-L, Lennmarkent C, Sandin R. Reduction in the incident of awareness using BIS monitoring. Acta Anaesthesiol Scand 48: 20-26, 2004. {Abstract}.
    1. Summary: The authors compared a group of patients with anesthetic depth guided by a brain function monitor (BIS®) to a historical group of patients anesthetized without the monitor. The monitored group had 0.04% incidence of awareness, while the historical group had 0.18% incidence of awareness. However, the study design could not rule out other causes for the reduction in awareness, such as changes in anesthesia drugs or practice.
  2. Myles PS, Leslie K, McNeil J, Forbes, Chan MTV. Bispectral index monitoring to prevent awareness during anaesthesia: The B-Aware randomized controlled trial. The Lancet 363: 1757-1763, 2004. {Abstract}
    1. Summary: The authors found that BIS monitoring lowered the risk of awareness by 82%, in a group of patients at high risk for awareness during general anesthesia.
  3. Apfelbaum JL, Arens JF, Cole DJ, et al. Practice Advisory for Intraoperative Awareness and Brain Function Monitoring: A Report by the American Society of Anesthesiologists Task Force on Intraoperative Awareness. Anesthesiology 104: 847-64, 2006. {Abstract}
    1. Summary: The Practice Advisory summarizes the risk factors associated with intraoperative awareness and offers guidelines for the intraoperative use of brain functioning monitors. The decisions for using a brain function monitor should be made on a case-by-case basis.
  4. Avidan MS, Zhang L, Burnside BA, Finkel KJ, Searleman AC, Selvidge JA, Saager L, Turner MS, Rao S, Bottros M, Hantler C, Jacobsohn E, & Evers, AS. Anesthesia awareness and the Bispectral Index. The New England Journal of Medicine 358: 1097-1108, 2008. {Abstract}
    1. Summary: The authors compared a group of patients with an end-tidal anesthetic gas anesthesia (n=974) to a brain function monitor (BIS®) anesthetic depth (n=967). There were a total of four cases with “definite anesthesia awareness,” specifically two from each group. The types of controls used in this study were mandated anesthetic concentrations and audible alarms. The authors concluded that the results do not support the standard practice of routine BIS® monitoring.
  5. Orser BA. Depth-of-anesthesia monitor and the frequency of Intraoperative awareness. Editorial. The New England Journal of Medicine 358: 1189-1191: 2008. {Abstract}
    1. Summary: The author wrote an editorial response to the Avidan et al., publication. She addressed the study’s validity, relevance to anesthesiology practice, and the principle points of the findings.

Patient Satisfaction

  1. Myles PS, Williams DL, Hendrata M, Anderson H, Weeks AM. Patient satisfaction after anaesthesia and surgery: results of a prospective survey of 10,811 patients. British Journal of Anaesthesia 84 (1): 6-10, 2000. {Abstract}
    1. Summary: The authors addressed quality of care for patients after surgery. After interviewing over 10,000 patients the first day after surgery, 96.8% of them had a level of satisfaction with the anesthesia care. Patient dissatisfaction was correlated with factors such as the occurrence of nausea, vomiting, post-operative pain and awareness during anesthesia. Of these factors, awareness during anesthesia had the strongest relationship to patient dissatisfaction.

Psychological/Emotional Sequelae

  1. Blacher RS. On awakening paralyzed during surgery: A syndrome of traumatic neurosis. JAMA 234 (1): 67-68, 1975. {Abstract}
    1. Summary: This article describes some of the potential long-term negative health effects of awareness during general anesthesia. The description of what the author calls “traumatic neurosis” fit the symptoms of what is now called posttraumatic stress disorder.
  2. Moerman N, Bonke B, Oosting J. Awareness and recall during general anesthesia. Anesthesiology 79: 454-464, 1993. {Abstract}
    1. Summary: This study reviews the perceptions, memories, and health consequences of awareness in 26 patients. The consequences included sleep disturbances, nightmares, flashbacks, and anxiety. The helpless feeling of being unable to move due to anesthetic paralysis was identified as a particularly traumatic experience.
  3. Schwender D, Kunze-Kronawitter H, Dietrich P, Klasing S, Forest H, Madler C. Conscious awareness during general anaesthesia: Patients’ perceptions, emotions, cognition, and reactions. British Journal of Anaesthesia 80: 133-139, 1998. {Abstract}
    1. Summary: The researchers identified 45 patients with awareness from Internet and newspaper ads and referral from anesthesiologists. The patients reported their perceptions during awareness and the longer-term consequences to their health and daily life. The authors were unable to understand why some people suffer from significant long term after effects while others were less affected.
  4. Osterman JE, Hopper J, Heran WJ, Keane TM, van der Kolk BA. Awareness under anesthesia and the development of posttraumatic stress disorder. General Hospital Psychiatry 23: 198-204, 2001. {Abstract}
    1. Summary: The authors of this study interviewed 16 patients who had experienced awareness during general anesthesia and 10 patients who had received general anesthesia without awareness. Nearly 60% of patients who had experienced awareness had symptoms of posttraumatic stress disorder while none of the patients who had not had awareness had these symptoms. The patients with awareness were self–referred, referred by an anesthesiologist, or recruited from announcements in newspapers and hospitals. This may make the awareness experiences studied different from most other patient awareness experiences.
  5. Lennmarken C, Bildfors K, Enlund G, Samuelsson P, Sandin R. Victims of awareness. Acta Anaesthesiol Scand 46: 229-331, 2002. {Abstract}
    1. Summary: This article summarizes the findings of interviews done with 9 out of 18 patients who had experienced awareness during general anesthesia. Four of the nine patients were dealing with psychological health problems nearly two years after the experience of awareness. Some patients felt that the problems would go away if they did not talk about it and were unable to or chose not to ask for help.
  6. Lennmarken C, Sydsjo G. Pscyhological consequences of awareness and their treatment. Best Practice & Research Clinical Anaesthesiology 21 (3): 357-367: 2007. {Abstract; Full Text (reproduced with permission of publisher as PDF)}
    1. Summary: This article reviews psychological sequelae of awareness and more specifically defining posttraumatic stress disorder. It addressed the risk factors and possible evidence based treatments for posttraumatic stress disorder, such as cognitive behavioral therapy and eye movement desensitization reprocessing.
  7. Samuelsson P, Brudin L, Sandin RH. Late psychological symptoms after awareness among consecutively included surgical patients. Anesthesiology 106: 23-32, 2007. {Abstract}
    1. Summary: This is the first study that prospectively and consecutively identified patients with awareness. Other similar studies recruited patients from anesthesiologists or by patient self-referral, leading the authors to state that their study may be a more accurate picture of the patients who experience awareness, than other studies that recruited patients from referrals and advertisements. Thirty-three percent of the patients experienced late psychological symptoms afterward. In 40% of those patients, the symptoms lasted for more than 2 months, and 1 patient had a diagnosis of posttraumatic stress disorder.

Other

  1. Orser BA, Mazer CD, Baker A. Awareness during anesthesia. CMAJ 178 (2): 185-188, 2007. {Abstract}
    1. Summary: This commentary discussed that awareness during general anesthesia occurs in 1 to 2 cases per 1000 patients with approximately 36% of patients experiencing some level of pain. Some of the patient risk factors include age, drug resistance, substance abuse, or past experiences of anesthesia awareness. If anesthesia awareness does occur, they suggest that the patient should be assessed and receive some type of follow-up either by the anesthesiologist, or in some cases other mental health care professionals.
  2. Sneyd JR, Mathews DM. Memory and awareness during anaesthesia. British Journal of Anaesthesia 100 (6): 742-4, 2008. {Abstract}
    1. Summary: The authors provide an editorial that reviews the latest Memory and Awareness 7 conference, which brings together mental health professional and health professionals to discuss the latest trends in anesthesia awareness and the depth of consciousness monitors.