International psychogeriatrics
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Postoperative delirium is a common syndrome that is often mistaken for other psychiatric conditions, particularly depression. Numerous investigators have found a clear convincing association between delirium and increased morbidity and mortality. ⋯ Lastly, areas demanding immediate further investigation are identified. In particular, outcome studies with particular emphasis on the role of age and prior drug exposure are urgently needed.
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Delirium is often considered a global and nonspecific alteration in cerebral function. However, the recent clinical evidence for heterogeneity within the syndrome of delirium suggests that different systems of the brain may be important in different kinds of delirium. Some forms of delirium, such as anticholinergic toxicity and hepatic encephalopathy, may be caused by drugs or toxins acting on specific brain neurochemical systems. ⋯ Little is known about changes in these systems with aging. The well-known degeneration in cholinergic systems in Alzheimer's disease, and the sensitivity of individuals with Alzheimer's disease to anticholinergic toxicity, suggest a role of central cholinergic systems in anticholinergic delirium in demented patients. Further research into the involvement of the other systems in aging and delirium apparently would be fruitful.
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"Delirium" is a reversible confusional state. It results from widespread but reversible interference with the function of cortical neurons, as documented by diffuse slowing on EEG and decreases in cerebral metabolic rate. Delirium can be due to impairments in neuronal metabolism, in neurotransmission (notably cholinergic), or in input from subcortical structures. ⋯ So many disorders can precipitate delirium that the differential diagnosis tests every facet of one's knowledge of medicine. With aging, both normative changes in the brain and the increasing incidence of brain diseases predispose to the development of delirium. The brain damage responsible for a dementia can sensitize to the development of a superimposed delirium.
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Review Case Reports
Benzodiazepine-induced and anticholinergic-induced delirium in the elderly.
Encompassing the range from subtle cognitive impairments to frank delirium, toxicity due to benzodiazepines and to anticholinergic-containing compounds is reviewed. For benzodiazepines, an extensive literature suggests that they impair immediate and delayed memory, psychomotor performance, and subjective complaints of station. ⋯ Toxicity from anticholinergic compounds, detected by anticholinergic drug levels, is significantly correlated with the presence and severity of delirium in a number of settings including postoperative patients and elderly nursing home residents. Possible means of identifying the syndrome by prediction of dose and type of medication, as well as by quantitative EEG, are reviewed.