Tuesday, March 23, 2021

The Patient with Intraoperative Awareness Case File

Posted By: Medical Group - 3/23/2021 Post Author : Medical Group Post Date : Tuesday, March 23, 2021 Post Time : 3/23/2021
The Patient with Intraoperative Awareness Case File
Lydia Conlay, MD, PhD, MBA, Julia Pollock, MD, Mary Ann Vann, MD, Sheela Pai, MD, Eugene C. Toy, MD

Case 47
While taking call on the Labor and Delivery unit, you are called emergently to see a 28-year-old woman G1P0 with fetal distress for an emergent cesarean section. The patient is 5 ft 2 in, weighs 90 kg, and is otherwise healthy. Fetal heart tones show poor variability and a rate of 90 bpm. The patient has had an uneventful general anesthetic previously for an appendectomy.

Considering the emergent nature of the surgery, a general anesthetic is performed with a rapid-sequence induction utilizing propofol and succinylcholine. After a successful endotracheal intubation, 2% sevoflorane in 100% oxygen is started. Approximately 4 minutes after induction, a 7 lb 8 oz female infant is born with Apgar scores of 4 and 9. The baby does well and the rest of the anesthetic is uneventful.

During the postoperative anesthesia visit on the day following surgery, the patient reports to you that she recalls events that occurred during her procedure and felt that she was in pain but was unable to move.

➤ What is the most likely diagnosis?

➤ What are the next steps in caring for this patient?

The Patient with Intraoperative Awareness

Summary: A 28-year-old female patient reports recall after general anesthesia for an emergency caesarean section.
Most likely diagnosis: Awareness or recall during anesthesia, which can be of two types
A. Explicit recall which is conscious recall of events occurring during surgery and may or may not be associated with a sensation of pain and the inability to move.
B. Implicit recall which is nonspecific recognition of events occurring during surgery or a vague awareness of events occurring during surgery.

Next steps: This patient requires a thorough evaluation of the extent of her recall and may need additional consultative services such as psychiatry or counseling to deal with the emotional consequences of recall during surgery.


1. Review the incidence and factors associated with intraoperative awareness.
2. Describe why certain procedures may be associated with an increased incidence of intraoperative awareness.
3. Understand the steps in evaluating the patient who reports intraoperative awareness.

This particular patient has undergone an anesthetic and surgery that is associated with a higher than normal incidence of intraoperative awareness. Emergent caesarean section for fetal distress, particularly in a parturient who is hypotensive and bleeding, is one of the most complicated and difficult anesthetics to perform. The need for urgent delivery of the hypoxic fetus and to anesthetize a mother who is hypotensive demands that doses of anesthetic induction agents and inhalation agents be limited to avoid additional maternal hypotension and fetal hypoxia.

It is essential that this patient receives an honest and thorough postoperative visit. It is important to determine the extent of her recall, and to elicit whether the recall of intraoperative events is disturbing to her. Occasionally, patients experience recall of intraoperative events during emergency surgery, but are not particularly disturbed by the experience. Other patients are markedly traumatized by the recall of intraoperative events. Once the experience has been documented, the patient should be offered a variety of services to deal with any posttraumatic stress they may be experiencing because of
recall. These services can include counseling and psychiatric services and in some instances may require medication. It is essential that the patient’s feelings regarding intraoperative recall are not dismissed.

The Patient with Recall


INTRAOPERATIVE AWARENESS: Recall (either explicit or implicit) of
events occurring during general anesthesia in the operating room.

EXPLICIT RECALL: Remembering exact events that occurred with or without pain during the operation.

IMPLICIT RECALL: Recognition but not specific recall of events happening in the operating room during general anesthesia.

BISPECTRAL INDEX OR BIS MONITOR: A processed or spectral EEG which represents activity of the cerebral cortex. The EEG is very active when patients are awake but relatively quiet during anesthesia or natural sleep. The monitor processes the EEG signals into a single number with 100 representing fully awake and 0 representing electrical silence.

Intraoperative awareness is reported to occur in approximately 0.0068% to 0.13% of general anesthetics performed in the United States. Despite the somewhat rare nature of recall, it is one of the most feared complications of general anesthesia and surgery. In contrast to the increasing public interest, awareness, and discussion of the incidence of intraoperative awareness, the American Society of Anesthesiologist Closed Claims database of malpractice claims indicates that there has been no substantial change in the liability associated with recall during anesthesia in the 1990s compared to previous reporting periods. It is possible, however, that there has been an increase in claims and judgments awarded that have not yet been detected by this database (see Table 47–1).

Despite the inability to predict precisely which patients may experience intraoperative recall, it is possible to suggest which patients may be at higher risk. Grouped by procedure, those at highest risks include patients undergoing coronary artery bypass grafting surgery, cesarean section, and emergency or trauma surgery performed at night. Grouped by patient characteristics, those at highest risks include patients of a younger age, an increased body weight,






Claims for awareness

7 (1%)

57 (2%)

65 (2%)

Payment made

4 (67%)

32 (62%)

31 (52%)

Median payment amount in 1999 dollars




smokers, patients who are critically ill, and those who may have increased tolerance because of long-term use of alcohol, opiates, or amphetamines. Patients who primarily receive an opioid-based anesthetic rather than an inhalation anesthetic are also at higher risk for recall, as are patients who receive muscle relaxants during surgery.

Differing states of wakefulness and recall may be reported by different patients. The smallest group of patients experiencing recall (0.03%) report conscious awareness and pain during surgery, and a desire “to scream during surgery but not being able to move.” It is this group of patients that is most likely to experience symptoms of posttraumatic stress secondary to recall during surgery. A higher percentage of patients (0.1%-0.2%) may report nonpainful but explicit recall of intraoperative events. These patients may be able to report verbatim conversations that occurred in the operating room during surgery, but do not report concomitant feelings of pain. The final group of patients may report nonspecific or amnesic awareness during surgery. These patients do not recall specific events or conversations that occur during surgery, but may have recognition recall of intraoperative events (Table 47–2).



Patient characteristics

Younger age, increased weight, smokers, long-term use of EtOH, opiates, or amphetamines

Types of surgery

Cesarean section, coronary artery bypass grafting, emergency surgery at night, trauma surgery

Anesthetic techniques

Muscle relaxants, narcotic-based techniques, inadequate dosing, equipment malfunctions such as empty vaporizers





Patient awake and fully alert


Patient anesthetized or natural sleep


Electrical silence, no cerebral activity

Manufacturers of processed EEG monitors have speculated that these monitors can reduce the incidence of intraoperative awareness. The company’s formula for arriving at the bispectral index (BIS) number is proprietary but is predominantly determined by the patient’s EEG. Manufacturers suggest that the ideal range for anesthetic management and decreased intraoperative awareness is a BIS level of 40 to 60. Recent large randomized studies have indicated that the BIS monitor is no more reliable in preventing recall of intraoperative events than monitoring of the end-tidal concentrations of inhaled anesthetic agents. The BIS monitor is also not reliable at the extremes of age. In addition, certain anesthetics (nitrous oxide or NMDA antagonists such as ketamine) unquestionably produce anesthesia, but not a decrease in the BIS number because they cause less EEG suppression than other anesthetic drugs (Table 47–3).

Comprehension Questions
47.1. Which of the following statements is accurate regarding the prevention of awareness?
A. A compressed EEG or BIS monitor level of 40 to 60 during general anesthesia guarantees that patients will not have recall of intraoperative events.
B. An end-tidal gas concentration of MAC guarantees that patients will not have recall of intraoperative events.
C. An end-tidal gas concentration of twice MAC guarantees that patients will not have recall of intraoperative events.
D. There are no ways to guarantee that patients will not have recall of intraoperative events.

47.2. Which of the following anesthetics techniques is associated with an increased incidence of intraoperative awareness?
A. Sevoflurane anesthesia
B. Propofol infusion
C. Nitrous oxide
D. Fentanyl infusion
E. Desflurane anesthesia

47.3. A 60-year-old female patient reports that during a previous anesthetic she experienced recall of a conversation occurring during surgery. An appropriate response includes which of the following?
A. Tell the patient that it was all her imagination.
B. Reassure the patient that with new anesthetic agents recall does not really happen.
C. Blame the surgeon for talking too loudly.
D. Reassure the patient and tell her that you will use a BIS monitor so you are sure she will not have recall.
E. Reassure the patient and tell her that you will employ techniques in an attempt to minimize the risks of recall.

47.1. D. Unfortunately there is no way even with monitoring to guarantee that patients will not have recall of intraoperative events. Studies have shown that monitoring the end-tidal concentration of inhalation anesthetic agents is as reliable in preventing recall as using an awareness monitor, and either of these methods is superior to observing for signs of sympathetic stimulation, seeming to indicate pain.

47.2. D. Fentanyl infusion. Primarily narcotic-based techniques have been shown to be associated with a higher incidence of intraoperative awareness than inhalation anesthetic techniques. This is because narcotic-based techniques do not provide for amnesia. Anytime a narcotic is used for the primary anesthetic agents, supplemental amnesic agents should be administered as well.

47.3. E. Patients who have experienced intraoperative recall are understandably very anxious about subsequent anesthetics. Unfortunately, there is no way to guarantee a patient that they will not experience intraoperative awareness. Using inhalation-based general anesthetic techniques with amnesic agents and careful monitoring of the EEG or end-tidal concentration of inhalation agents are the best way to minimize the chances of intraoperative recall. 

Clinical Pearls
➤ The incidence of intraoperative awareness is estimated to be 0.8%.
➤ Certain procedures including cesarean section, cardiac surgery with cardiopulmonary bypass, and trauma surgery are associated with an increased incidence of intraoperative awareness.
➤ Although techniques such as monitoring end-tidal gas concentrations and the compressed EEG reduce the incidence of awareness, there is no monitor which can guarantee against intraopertive awareness.


Avidan MS, Zhang L, Burnside BA, et al. Anesthesia awareness and the bispectral index. N Engl J Med. 2008:358;1097. 

Kent CD. Liability associated with awareness during anesthesia. ASA News. 2006;70(6):8-10.


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