Case Description

A 34-year-old, 92-kg gravida 1 para 0 woman with no significant medical history presented to the labor and delivery unit at 39 weeks’ gestation after spontaneous rupture of membranes. Episodes of prolonged fetal bradycardia were detected on the fetal monitor, and prolapsed umbilical cord was diagnosed. The patient was promptly taken to the OR for an emergent cesarean delivery (CD). General anesthesia was induced with 200 mg of propofol and 100 mg of succinylcholine. The first intubation attempt with direct laryngoscopy failed using a Macintosh No. 3 blade. A 6.5-mm endotracheal tube was inserted successfully on the second attempt using a GlideScope (Verathon). Anesthesia was maintained with 50:50 nitrogen oxide and oxygen, together with sevoflurane to a minimum alveolar concentration (MAC) of 0.7. After delivery of a newborn boy with Apgar scores of 7 and 9, 100 mcg of fentanyl, 20 mg of rocuronium and 5 IU of oxytocin were administered. At the end of the 65-minute surgery, neuromuscular blockade was reversed with neostigmine and glycopyrrolate. Extubation was uneventful.

The next day, the patient reported hearing conversations and experiencing sharp abdominal pain during the operation. Accidental intraoperative awareness was suspected. A structured postoperative interview confirmed the suspicion of accidental awareness during general anesthesia (AAGA). The attending anesthesiologist spoke to her in depth about the incident and apologized for the event. She was offered counseling and seen by the psychiatry team. A follow-up interview was scheduled after one week.

The American Society of Anesthesiologists Practice Advisory for Intraoperative Awareness and Brain Function Monitoring defines awareness as when “a patient becomes conscious during a procedure performed under general anesthesia and subsequently has recall of these events.”1AAGA is rare; estimates of incidence vary largely depending on the patient population studied and the definition of awareness used by the researchers.2-4 A multicenter prospective study in the United States estimated the incidence of AAGA to be 1 to 2:1,000.2 The 5th National Audit Project (NAP5) found the incidence of AAGA spontaneously reported by the patient to be 1:19,000, with most cases occurring between the induction of general anesthesia and the start of surgery. The incidence varied with the surgical procedure and patient comorbidities. AAGA for CD was significantly higher, at 1:670.3

Risk Factors for Awareness During CD

There are many risk factors for AAGA during CD (Table). Most general anesthetics for CD are done in emergency circumstances with rapid sequence induction (RSI) necessitating neuromuscular blocking agents (NMBAs). The use of NMBAs can mask physical signs of inadequate anesthetic depth. NAP5 found a much higher incidence of AAGA when NMBAs were used (1:8,200) as opposed to cases without their use (1:135,900).3

Table. Risk Factors for AAGA in CD
Administration of neuromuscular blocking agents
Avoidance of opioids before cord clamping
Avoidance of sedative premedication
Difficult airway causing prolonged time to intubation
Female sex
High incidence of emergency procedures
Inadequate depth of anesthesia
Increased cardiac output affecting the uptake and distribution of volatile anesthetics
Low doses of induction agents
Rapid sequence induction
Younger age
AAGA, accidental awareness during general anesthesia; CD, cesarean delivery

Based on references 2-4.

Typically, opioids are omitted before cord clamping due to concern over transplacental drug transfer resulting in respiratory depression in the newborn. A recently published survey of RSI for CD in England showed that only 9% of anesthesiologists routinely administer opioids at induction of general anesthesia.5 This practice has been questioned, especially with the increased availability of short-acting opioids, such as remifentanil. As for the potential adverse fetal consequences, there is a paucity of studies adequately powered to investigate the effect of opioid administration prior to delivery on neonatal outcomes.6,7

Obesity is frequent during pregnancy, increasing the risk for AAGA. Traditionally, lower MACs of volatile agents are used during CD to avoid neonatal depression and uterine atony and considering lower anesthetic requirements during pregnancy. However, the optimal concentration of volatile anesthetics for maintenance of anesthesia after delivery of a newborn has not been fully investigated, and the value of bispectral index (BIS) monitoring in detecting awareness during CD is controversial.8 Ueyama et al showed no difference between pregnant and nonpregnant patients in EEG measures during maintenance of anesthesia with sevoflurane.9 Chin and Yeo showed that median effective end-tidal concentration of sevoflurane of 1.2% is required to maintain a BIS less than 60 before delivery.10 Difficult airway management is a well-known problem in the parturient, further increasing the risk for AAGA.

Post-op Detection of AAGA

The most frequently used tool to identify AAGA in the postoperative period is a structured interview based on the questionnaire developed by Brice et al in 1970.11 Not all patients experiencing AAGA will spontaneously report their experience, and using random questions as opposed to a structured interview is less likely to detect AAGA.2 It is recommended to conduct the postoperative interview in the PACU and later in a follow-up interview at least one week after general anesthesia. Sebel et al reported that approximately 50% of cases of AAGA were detected in a follow-up interview.2 The authors used a modified Brice questionnaire and added a question: “Do you remember anything between going to sleep and waking up?”

Mashour et al developed a classification instrument for AAGA. Known as the “Michigan Awareness Classification Instrument,” the authors suggest five classes as an expression of AAGA: “no awareness, isolated auditory perceptions, tactile perceptions, pain, and paralysis.” An additional designation of “D” for distress was added to reflect patient reports of fear, anxiety, a sense of doom, and other such descriptions.12 Patients with a previous episode of AAGA present a fivefold increased risk for developing AAGA during subsequent general anesthesia.13

Psychological Sequelae After AAGA

AAGA can lead to serious immediate and late psychological sequelae, such as post-traumatic stress disorder (PTSD). These include sleep disturbances, nightmares, flashbacks, daytime anxiety, fear of future anesthetics and impaired job performance.14,15 Ghoneim et al analyzed 271 cases of awareness, reporting that 22% of patients experienced late psychological symptoms, including PTSD.14

The NAP5 authors suggested three steps for managing AAGA: meeting the patient, analyzing the event, and offering support.3 When meeting the patient it is important to listen, show empathy, apologize for the event, and explain reasons for AAGA. The symptoms described by the patients and details of the conversation should be documented. A structured interview will help to identify the extent of the event and analyze possible factors leading to AAGA. Follow-up visits and phone calls should be scheduled and physiologic/psychiatric consultation and support offered.14,15


  • The incidence of AAGA during general anesthesia for CD is significantly higher compared with general populations.
  • BIS monitoring in conjunction with clinical signs can help adjust anesthetic depth.
  • Structured postoperative questionnaires are helpful to detect AAGA.
  • Psychological sequelae after AAGA can be prolonged and severe.
  • Empathy and physiologic support in patients with AAGA are crucial.

Dr. Clarke is a resident in the Department of Anesthesiology and Perioperative Medicine, and medical director of perioperative services; Dr. Vaida is a professor of anesthesiology and perioperative medicine, and obstetrics and gynecology; the vice chair of research; and the director of obstetric anesthesia at Penn State Health Milton S. Hershey Medical Center, in Hershey, Pa.

The author and reviewer reported no relevant financial disclosures.


  1. Practice advisory for intraoperative awareness and brain function monitoring: a report by the American Society of Anesthesiologists Task Force on Intraoperative Awareness. Anesthesiology. 2006;104(4):847-864.
  2. Sebel PS, Bowdle TA, Ghoneim MM, et al. The incidence of awareness during anesthesia: a multicenter United States study. Anesth Analg. 2004;99(3):833-839.
  3. Pandit JJ, Andrade J, Bogod DG, et al; Royal College of Anaesthetists and the Association of Anaesthetists of Great Britain and Ireland. The 5th National Audit Project (NAP5) on accidental awareness during general anaesthesia: summary of main findings and risk factors. Anaesthesia. 2014;69(10):1089-1101.
  4. Paech MJ, Scott KL, Clavisi O, et al; ANZCA Trials Group. A prospective study of awareness and recall associated with general anaesthesia for caesarean section. Int J Obstet Anesth. 2008;17(4):298-303.
  5. Desai N, Wicker J, Sajavan A, et al. A survey of practice of rapid sequence induction for caesarean section in England. Int J Obstet Anesth. 2018;36:3-10.
  6. Patel S, Fernando R. Opioids should be given before cord clamping for caesarean delivery under general anaesthesia. Int J Obstet Anesth. 2016;28:76-80.
  7. Loubert C, Zaphiratos V. Opioids given before cord clamping for cesarean delivery under general anesthesia. Int J Obstet Anesth. 2016;28:80-82.
  8. Zand F, Hadavi SM, Chohedri A, et al. Survey on the adequacy of depth of anaesthesia with bispectral index and isolated forearm technique in elective Caesarean section under general anaesthesia with sevoflurane. Br J Anaesth. 2014;112(5):871-878.
  9. Ueyama H, Hagihira S, Takashina M, et al. Pregnancy does not enhance volatile anesthetic sensitivity on the brain: an electroencephalographic analysis study. Anesthesiology. 2010;113(3):577-584.
  10. Chin KJ, Yeo SW. BIS-guided study of sevoflurane requirements for adequate depth of anaesthesia in Caesarean section. Anaesthesia. 2004;59(11):1064-1068.
  11. Brice DD, Hetherington RR, Utting JE. A simple study of awareness and dreaming during anaesthesia. Br J Anaesth. 1970;42(6):535-542.
  12. Mashour GA, Esaki RK, Tremper KK, et al. A novel classification instrument for intraoperative awareness events. Anesth Analg. 2010;110(3):813-815.
  13. Aranake A, Gradwohl S, Ben-Abdallah A, et al. Increased risk of intraoperative awareness in patients with a history of awareness. Anesthesiology. 2013;119(6):1275-1283.
  14. Ghoneim MM, Block RI, Haffarnan M, et al. Awareness during anesthesia: risk factors, causes and sequelae: a review of reported cases in the literature. Anesth Analg. 2009;108(2):527-535.
  15. Tasbihgou SR, Vogels MF, Absalom AR. Accidental awareness during general anaesthesia—a narrative review. Anaesthesia. 2018;73(1):112-122.