Best practice & research. Clinical anaesthesiology
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Best Pract Res Clin Anaesthesiol · Sep 2007
Monitoring consciousness: the current status of EEG-based depth of anaesthesia monitors.
Direct and indirect inhibitory effects of anaesthetic agents on cortical activity are reflected in the electroencephalogram (EEG) as: (i) a shift from low-amplitude, high-frequency EEG, to high-amplitude, low-frequency activity (indicative of cortical depowering) and; (ii) the appearance of spindles and K-complexes (indicative of thalamocortical hyperpolarisation and sensory blockade). Existing EEG monitors use cortical activity as a proxy measure for consciousness. ⋯ Also the literature reveals many instances where the EEG pattern is dissociated from conscious state (e.g. an awake-looking EEG, but an unresponsive patient; or a slow-wave EEG in an awake patient). Fortunately, a slow-wave EEG (even in the presence of a responsive patient) usually indicates profound amnesia for explicit memory.
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Increased attention in recent years in both the academic literature and general media on awareness during general anaesthesia has raised the spectre of an increase in the liability burden of anaesthesia awareness. Liability will be different around the world, largely influenced by factors such as the presence of no-fault compensation systems for medical complications in some countries and the characteristics of the common law tort systems in others, such as the United States. A review of the largest single source for liability data, the American Society of Anesthesiologists' Closed Claims database, found the proportion of anaesthesia malpractice claims and claim payment amounts for awareness did not increase during the 1990s. However, due to the time lag to settlement of claims, this data predates recent attention to awareness and electroencephalographic monitoring, factors that may increase liability for awareness in the future.
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Best Pract Res Clin Anaesthesiol · Sep 2007
Awareness, dreaming and unconscious memory formation during anaesthesia in children.
Recent studies have reported an incidence of awareness in children of around 1%, while older studies reported incidences varying from 0% to 5%. Measuring awareness in children requires techniques specifically adapted to a child's cognitive development and variations in incidence may be partly explained by the measures used. The causes and consequences of awareness in children remain poorly defined, though a consistent finding is that many children do not seem distressed by their memories. ⋯ Compared to explicit memory, implicit memory is more robust in young children; however there is no evidence yet for implicit memory formation during anaesthesia in children. Children less than 3 years of age do not form explicit memory, although toddlers, infants and even neonates have signs of consciousness and implicit memory formation. In these very young children the relevance of awareness remains largely unknown.
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Best Pract Res Clin Anaesthesiol · Sep 2007
Incidence of and risk factors for awareness during anaesthesia.
Explicit recall of events during general anaesthesia is detected by direct questioning, as patients may not report awareness spontaneously or if they are questioned non-specifically. More than one interview is needed and credibility of reports should always be verified. ⋯ Studies of patients recruited through referrals by colleagues or advertisements, studies of compensation claims and those carried out through quality improvement systems are inadequate. Several factors increase the risk of awareness, including light anaesthesia, some types of surgery, a history of awareness, chronic use of central nervous system depressants, younger age, obesity, inadequate or misused anaesthesia delivery systems, insufficient knowledge about awareness, and ignoring the use of electroencephalographic monitors when the risk is otherwise increased.
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Best Pract Res Clin Anaesthesiol · Sep 2007
Psychological consequences of awareness and their treatment.
Intraoperative awareness with subsequent recall is a rare but serious complication with an incidence of 0.1-0.2%. In approximately one third of the patients who have experienced awareness, late severe psychiatric sequelae may develop. The psychiatric symptoms in these patients fulfil the diagnostic criteria for post traumatic stress disorder. ⋯ The problem must be acknowledged. Professional psychiatric assessment and follow up should constitute standard practice. The treatments of choice are Eye Movement Desensitisation Reprocessing and Cognitive Behaviour Therapy.