Reported memory
Prevalence (%)
Hearing
85–100
Seeing
27–46
Fear
78–92
Helplessness
46
Operation details
64
Paralysis
60–89
Pain
39–42
The main causes of awareness are light anesthesia, increased anesthetic requirement, and equipment malfunction. In most cases, awareness arises in patients who have planned light anesthesia or when lower doses of anesthetic agents are required. These patients/surgeries include:
General anesthesia for cesarean section
Scoliosis operations with intraoperative wake-up testing
Cardiac surgery patients, especially during cardiopulmonary bypass
Bronchoscopy
Patients with severe cardiac dysfunction
Trauma surgery
Although light anesthesia is commonly manifest by hypertension and tachycardia, hemodynamics are usually unpredictable indicators of awareness. Reliance on observation of clinical signs fails as soon as autonomic reactions are masked by medications such as catecholamines, antihypertensives, parasympatholitics, etc. The pain response is masked by opioids and movement is prevented by muscle relaxants. Don’t forget the increased anesthesia dose required in younger patients, patients with any history of drug abuse, and patients taking chronic opioids and benzodiazepines. Many episodes of awareness occur in hypotensive patients in whom anesthesia doses are reduced to avoid cardiovascular depression.
8.1.9 What Are the Psychological Sequelae of Awareness in Patients?
The psychological sequelae are dependent on the remembered experiences. They include, with increasing severity:
Anxiety
Sleeping disorders
Nightmares
Constant reliving of the intraoperative perceived events
Death-like experience
Avoiding situations which are similar to the intraoperative awareness: doctors, hospitals, and surgery
Full-blown posttraumatic stress disorder (PTSD)
Minimal impairments are common, but some patients develop PTSD. The incidence of PTSD after an awareness episode is unclear and may be associated with more distress, pain, and near-death experience.
8.1.10 What Are Some Strategies to Prevent Awareness?
In surgical procedures with an increased risk of intraoperative awareness, increased vigilance is needed. In these patients, the possibility of awareness should be discussed preoperatively. In most patients without an increased risk, failing to bring up the possibility of awareness can be justified by the desire to avoid causing undue worry in countless patients.
8.1.10.1 Prophylaxis Against Awareness
The most important preventive strategy against awareness is possibly the pharmcological premedication with bezodiazepines [13]
Benzodiazepines are administered before induction of anesthesia for most elective procedures. However, benzodiazepines are often avoided in emergency surgery. Limiting muscle relaxants to the minimum necessary is recommended. The loss of consciousness must be maintained for as long as the patient is still paralyzed. Measuring the degree of neuromuscular blockade with a TOF monitor is important to avoid complete neuromuscular blockade.
Furthermore, operating room discussions should be kept to a minimum, with conversations in quiet voices. Comments or insults about the patient are strictly inappropriate.
Anesthetics depress consciousness and unconscious perceptions in a dose-dependent manner. Therefore, high enough doses should be given, which is especially important for RSI patients [8]. In order to prevent awareness, the end-tidal anesthetic concentration of the volatile anesthetic needs to be 0.7 MAC or greater, adjusted for age [2]. MAC levels decrease with age. The monitoring of the end-tidal volume of anesthetic concentration only shows that the concentration is high enough, not necessarily guaranteeing a protective effect against awareness. In most cases of anesthesia care, lower MAC levels are given in combination with opioids and occasionally nitrous oxide.
Until now, there has been controversy over which type of anesthesia has the highest incidence of awareness: balanced with volatile agents or total intravenous anesthesia (TIVA). New data show a higher incidence during TIVA [6]. TIVA requirements vary considerably among patients. In addition, the lack of end-tidal anesthetic gas concentrations and greater chance of administration errors also increase the risk of awareness with TIVA. Brain function monitors may be useful in assessing anesthetic depth. Most are based upon analysis of EEG activity, as changes in consciousness create predictable EEG changes. Even acoustic evoked potentials are done for determining anesthesia depth. Titration of anesthesia using the bispectral index (BIS) monitor, a brain function monitor using cortical EEG, reduced the incidence of awareness, but did not completely prevent it, in patients at high risk for awareness [11]. While similarly effective in reducing awareness as use of end-tidal anesthetic gas levels during inhalational anesthesia [2], use of a brain function monitor is recommended to assess the degree of hypnosis during TIVA [3].
Many patients with awareness remember conversations during surgery as the block of sound impulses during general anesthesia is not reliable. For this reason, it may be beneficial to cover the ears of patients at increased risk for awareness.
If awareness occurs, the complaints of the patients must be taken seriously. An empathetic discussion with the patient and an explanation of the events is important. Subsequently, patients should be referred to a mental health specialist for counseling. It is unclear if immediate counseling can reduce the likelihood of serious psychological sequelae, but referral is standard care.
>> Dr. Eldridge took a good hard look at me after our discussion about awareness. “This is a very uncomfortable situation for me. I am very sorry. Honestly, I offer you my deepest apologies. If you develop nightmares or anxiety attacks as a result of this experience, please contact me immediately. I also recommend you obtain psychological counseling, as it may help prevent severe psychological problems from developing.”
I assured him it was OK, that I did not need psychological counseling, and I promised to contact him no matter what within the next few months. Somehow, however, it took a year before I managed to get him on the phone. During the first 2 weeks after surgery, I sometimes dreamed of the “equipment moving around in my stomach,” but then the dreams went away. Today I can talk about it all normally, without emotional difficulty and without breaking out in a cold sweat. Thanks for listening.
Related posts:
Full access? Get Clinical Tree
