Awareness During Anesthesia: Risk Factors, Causes and Sequelae: A Review of Reported Cases in the Literature

Department of Anesthesia, University of Iowa, Iowa City, Iowa, USA.
Anesthesia and analgesia (Impact Factor: 3.47). 02/2009; 108(2):527-35. DOI: 10.1213/ane.0b013e318193c634
Source: PubMed


Awareness during anesthesia is uncommon. The number of cases that are found in one single study are insufficient to identify and estimate the risks, causal factors and sequelae. One method of studying a large number of cases is to analyze reports of cases of awareness that have been published in scientific journals.
We conducted an electronic search of the literature in the National Library of Medicine's PubMed database for case reports on "Awareness" and "Anesthesia" for the time period between 1950 through August, 2005. We also manually searched references cited in these reports and in other articles on awareness. We used two surgical control groups for comparative purposes. The first group in a study by Sebel et al. consisted of patients who did not experience awareness. The second group, from the 1996 data from the National Survey of Ambulatory Surgery included patients who received general anesthesia. We also used data from the National Center for Health Statistics to compare weight and Body Mass Index.
We compared the data of 271 cases of awareness with 19,504 patients who did not suffer it. Aware patients were more likely to be females (P < 0.05), younger (P < 0.001) and to have cardiac and obstetrics operations (P < 0.0001). Only 35% reported the awareness episode during the stay in the recovery room. They received fewer anesthetic drugs (P < 0.0001), and were more likely to exhibit episodes of tachycardia and hypertension during surgery (P < 0.0001). A much larger percentage of these patients (52%, P < 0.0001) voiced postoperative complaints related to awareness. Inability to move and feelings such as helplessness, sensation of weakness, and hearing noises and voices were related to the persistence of complaints such as sleep disturbances and fear about future anesthetics (P < 0.041-0.0003). Twenty-two percent of the patients suffered late psychological symptoms.
Our review suggested light anesthesia and a history of awareness as risk factors. Obesity and avoidance of nitrous oxide use did not seem to increase the risk. Light anesthesia was the most common cause. Our findings suggest preventive procedures that may lead to a decrease in the incidence of awareness.

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    • "Patients with addiction require a greater amount of anesthetic drugs; thus, those patients have an increased likelihood of experiencing intraoperative awareness [28,29]. A previous history of awareness is a strong predisposing factor that increases the incidence of a new intraoperative awareness to 1.6% [30]. In patients with difficulty airways, the incidence of intraoperative awareness is 4.5-7.5% [31]. "
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    ABSTRACT: Anesthesia awareness is defined as both consciousness and recall of surgical events. New research has been conducted out to test this phenomenon. However, testing methods have not proven reliable, including those using devices based on electroencephalographic techniques to detect and prevent intraoperative awareness. The limitations of a standard intraoperative brain monitor reflect our insufficient understanding of consciousness. Moreover, patients who experience an intraoperative awareness can develop serious post-traumatic stress disorders that should not be overlooked. In this review, we introduce the incidence of intraoperative awareness during general anesthesia and discuss the mechanisms of consciousness, as well as risk factors, various monitoring methods, outcome and prevention of intraoperative awareness.
    Korean journal of anesthesiology 05/2014; 66(5):339-345. DOI:10.4097/kjae.2014.66.5.339
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    • "Two more recent studies report even higher incidences of 1% and 0.4% [2], [3]. The phenomenon is frequently described [4]–[6] and several monitors of depth of anesthesia (e.g. Bispectral Index; Entropy Module) are now in clinical use. "
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    ABSTRACT: During 0.1-0.2% of operations with general anesthesia, patients become aware during surgery. Unfortunately, pharmacologically paralyzed patients cannot seek attention by moving. Their attempted movements may however induce detectable EEG changes over the motor cortex. Here, methods from the area of movement-based brain-computer interfacing are proposed as a novel direction in anesthesia monitoring. Optimal settings for development of such a paradigm are studied to allow for a clinically feasible system. A classifier was trained on recorded EEG data of ten healthy non-anesthetized participants executing 3-second movement tasks. Extensive analysis was performed on this data to obtain an optimal EEG channel set and optimal features for use in a movement detection paradigm. EEG during movement could be distinguished from EEG during non-movement with very high accuracy. After a short calibration session, an average classification rate of 92% was obtained using nine EEG channels over the motor cortex, combined movement and post-movement signals, a frequency resolution of 4 Hz and a frequency range of 8-24 Hz. Using Monte Carlo simulation and a simple decision making paradigm, this translated into a probability of 99% of true positive movement detection within the first two and a half minutes after movement onset. A very low mean false positive rate of <0.01% was obtained. The current results corroborate the feasibility of detecting movement-related EEG signals, bearing in mind the clinical demands for use during surgery. Based on these results further clinical testing can be initiated.
    PLoS ONE 09/2012; 7(9):e44336. DOI:10.1371/journal.pone.0044336 · 3.23 Impact Factor
    • "[151] [152] [153] It is clear that information can, in fact, be processed in the anesthetized state, but cannot be integrated to form perception. [154] The rare cases of awareness during anesthesia may reflect incomplete or inadequate unbinding. [150] [155] [156] Binding abnormalities have been suggested in numerous other neuropsychiatric conditions including: • Alzheimer's disease [157] • Attention deficit hyperactivity disorder (ADHD) [157] [158] • Bipolar affective disorder [159] • Delirium [160] • Depression [161] • Disorders of Arousal • Hallucinogenic drugs • Neurogenic pain [161] • Parkinson's disease [161] • Schizophrenia, Autism, and Asperger syndrome [162- 168] [169] [170] [171] [172] [173] [174] [175] (Abnormalities have also been found in asymptomatic first-degree relatives of schizophrenics). • Sensory synesthesia [176] • Spatial neglect. "
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    ABSTRACT: Sleep is clearly not only a whole-brain or global phenomenon, but can also be a local phenomenon. This accounts for the fact that the primary states of being (wakefulness, NREM sleep, and REM sleep) are not necessarily mutually exclusive, and components of these states may appear in various combinations, with fascinating clinical consequences. Examples include: sleep inertia, narcolepsy, sleep paralysis, lucid dreaming, REM sleep behavior disorder, sleepwalking, sleep terrors, out-of-body experiences, and reports of alien abduction. The incomplete declaration of state likewise has implications for consciousness - which also has fluid boundaries. Fluctuations in the degree of consciousness are likely explained by abnormalities of a "spatial and temporal binding rhythm" which normally results in a unified conscious experience. Dysfunctional binding may play a role in anesthetic states, autism, schizophrenia, and neurodegenerative disorders. Further study of the broad spectrum of dissociated states of sleep and wakefulness that are closely linked with states of consciousness and unconsciousness by basic neuroscientists, clinicians, and members of the legal profession will provide scientific, clinical and therapeutic insights, with forensic implications.
    Current topics in medicinal chemistry 08/2011; 11(19):2392-402. DOI:10.2174/156802611797470277 · 3.40 Impact Factor
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