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 is one of the first large-scale studies examining the incidence of awareness in the United States. In this study, researchers reported that the incidence of awareness in seven academic medical centers throughout the United States is comparable to those of other countries. Out of 19, 575 patients, 25 patients were identified as experiencing awareness (e.g. incidence of 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.
  4. Mashour GA, Wang LYJ, Turner CR, Vandervest JC, Shanks A, Tremper KK. A retrospective study of intraoperative awareness with methodological implications. Anesth Analg 108, (2), 521-536, 2009 {Abstract}
    1. Summary: Standard evaluations are done postoperatively at the authors’ institution and information on awareness is listed. Regardless of the anesthetic type, evaluations are completed. This study is a chart review of 65,061 patients receiving general anesthesia and 51,417 receiving other types of anesthesia. The incidence rate of awareness from 44,006 patients receiving general anesthesia was 0.023% or 1/4401 patients. The incidence among 22,885 patients who had other types of anesthesia was 0.03% of 1/3269 patients.

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.
  6. Ghoneim, MM, Block RI, Haffarnan M, Mathews MJ. Awareness during anesthesia: Risk factors, causes and sequelae: A review of reported cases in literature. Anesthesia and Analgesia 108, (2), 527-535, 2009. {Abstract}
    1. Summary: In this article, the authors reviewed published cases of awareness during general anesthesia compared with patients who had no recall of awareness. 271 cases of awareness were compared with 19, 504 patients who did not experience awareness. The authors found that only 35% of patients reported the awareness episode in the recovery room. This review revealed two risk factors: light anesthesia and a history of awareness.
  7. Mashour GA, Orser BA, Avidan MS. Intraoperative awareness: from neurobiology to clinical practice. Anesthesiology 114(5)1218-33, 2011. {Abstract}
    1. Summary: In this review article, the authors discuss the neurobiology of consciousness and memory as it relates to intraoperative awareness. Through a better-understanding of the underlying neurobiology of anesthesia awareness, new methods to monitor anesthesia can be developed and a more reliable method of prevention may be found.

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: In 2004, researchers conducted a study to see whether BIS monitoring would reduce the incidence of awareness during surgery in adults. In the group using BIS, 2 instances of awareness were reported, while in the control group 11 were reported. The researchers concluded that BIS-guided anesthesia reduced the risk of awareness by 82%.
  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.
  6. Leslie K, Myles, PS, Forbes, A, Chan, MTV. The Effects of Bispectral Index Monitoring on Long-Term Survival in the B-Aware Trial. Anesthesia and Analgesia 110, (3), 816-822, 2010. {Abstract}
    1. Summary: The authors conducted a follow-up analysis of the B-Aware Trial to test the hypothesis that patients who had received BIS-guided anesthesia would be more likely to survive over those without it. The authors found that BIS monitoring was associated with reduced mortality rates in patients enrolled in the the B-Aware trial.

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. Psychological consequences of awareness and their treatment. Best Practice & Research Clinical Anaesthesiology 21 (3): 357-367: 2007. {Abstract}
    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.
  8. Mashour, GA, Wang, Ly-J, Esaki, RK, & Naughton, NN. Operating room desensitization as a novel treatment post-traumatic stress disorder after awareness Anesthesiology 109, (5), 927-929, 2008. {Abstract}
    1. Summary: This case report discusses a therapeutic treatment for posttraumatic stress disorder (PTSD) after awareness during general anesthesia for surgery. The patient took part in supportive counseling “in vivo” exposure for desensitization of the operating room. At the end of the patient’s treatment, the psychologist assessed that the patient was in PTSD remission.
  9. Bruchas RR, Kent CD, Wilson HD, Domino KB. Anesthesia Awareness: Narrative Review of Psychological Sequelae, Treatment, and Incidence. Journal of Clinical Psychology in Medical Settings, 2011 Apr. 22, [Epub ahead of print]. {Abstract}
    1. Summary: In this review article, the authors summarize patient recollections, psychological, sequelae, treatment, and follow-up of psychological consequences of intraoperative awareness. By increasing the recognition of awareness in psychological communities, the authors hope that practitioners will be better-equipped to treat patients who have had anesthesia awareness.

Pediatrics

  1. Iselin-Chaves I, Lopez U, Habre W. Intraoperative awareness in children: Myth or reality? Curr Opin Anaesthesiol 19:309-3:14, 2006 {Abstract}
    1. Summary: The authors reviewed the literature of awareness during surgery in children. Brice interviews were utilized to elicit any recall. The researchers found that while children describe similar memories as those described by adults, they do not appear to not suffer any long-term psychological consequences.
  2. Lopez U, Habre W, Laurencon M, Haller G, Van deer Linden M, & Iselin-Chaves IA. Intra-operative awareness in children: the value of an interview adapted to their cognitive abilities. Anaesthesia 62, 778-789, 2007 {Abstract}
    1. Summary: The authors used a semi-structured in-depth qualitative interview questionnaire designed for children to assess if awareness during general anesthesia occurred. Four hundred ten children were interviewed twice with an incidence rate of 1.2% for confirmed awareness cases. The incidence rate increased to 2.7% (11 cases) with confirmed and possible cases of awareness added together.
  3. Lopez U, Habre W, Vander Linden M, & Iselin-Chaves IA. Intra-operative awareness in children and post-traumatic stress disorder. Anaesthesia 63, 474-481, 2008 {Abstract}
    1. Summary: The authors explored whether children were psychologically impaired after experiencing anesthesia awareness. The children had previously consented to another study and were assessed as having had confirmed or possible awareness. After administering a PTSD questionnaire, none of the seven children had short or long-term psychological sequaelae. A limitation to the study is the small sample size.
  4. Blusse van Oud-Alblas HJ, Van Dijk M, Liu C, Tibbuel D, Klein J, Weber F. Intraoperative awareness during paediatric aneasethesia. BJA 102(1): 104-10, 2009. {Abstract}
    1. Summary: Children (aged 5-18 yr) that underwent elective or emergency surgery were surveyed three different times for awareness during general anesthesia. The interviews revealed that awareness occurred in 26 out of 928 children (0.6% incidence rate). Interestingly, the children reported no distress.
  5. Malviya S, Galinkin JL, Bannister CF, Burke C, Zuk J, Popenhagen M, Brown S, Voepel-Lewis T. The incidence of intraoperative awareness in children: Childhood awareness and recall evaluation. Anesth Analg 109(5):1421-7, 2009. {Abstract}
    1. Summary: In this article the authors explored the incidence of awareness in children for three different settings, factors involved in awareness, and if the children experienced short-term psychological consequences. Fourteen out of 1784 (0.8% incidence rate) children met the defined terms for possible/probable awareness. Children reported feeling scared (43%) and hurting (21%) during their surgery. None of the children experienced psychological consequences after the surgery.

 

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.
  3. Mashour, GA, Esaki, RK, Tremper, KK, Glick, DB, O’Conner, M, Avidan MS. A novel classification instrument for intraoperative awareness events. Anesth Analg 110(3): 813-5, 2010. {Abstract}
    1. Summary: The authors developed a classification instrument for physical and emotional events during awareness during general anesthesia for surgery. Class 0: No Awareness, Class 1: Isolated auditory perceptions, Class 3: Tactile perceptions, Class 3: Pain, Class 4: Paralysis, Class 5: Paralysis and pain, D = Distress.