Introduction
Background
Delirium or acute confusional state is a transient global disorder of cognition. The condition is a medical emergency associated with increased morbidity and mortality rates. Early diagnosis and resolution of symptoms are correlated with the most favorable outcomes. Therefore, it must be treated as a medical emergency.
Delirium is not a disease but a syndrome with multiple causes that result in a similar constellation of symptoms. Delirium is defined as a transient, usually reversible, cause of cerebral dysfunction and manifests clinically with a wide range of neuropsychiatric abnormalities. The clinical hallmarks are decreased attention span and a waxing and waning type of confusion.
Delirium often is unrecognized or misdiagnosed and commonly is mistaken for dementia, depression, mania, an acute schizophrenic reaction, or part of old age (patients who are elderly are expected to become confused in the hospital).
The word delirium is derived from the Latin term meaning "off the track." This syndrome was reported during Hippocrates' time, and, in 1813, Sutton described delirium tremens. Later, Wernicke described the encephalopathy that bears his name.
Case studyA 78-year-old female was brought to the Emergency Department by her daughter for vomiting, new onset urinary incontinence, confusion, and incoherent speech for the past 2 days. The patient was disoriented and could see people climbing trees outside the window. She had difficulty sustaining attention, and her level of consciousness waxed and waned. She had been talking about her deceased husband. Patient was also trying to pull out her intravenous access line. Past history included diabetes mellitus, hyperlipidemia, osteoarthritis, and stroke.
The patient's family physician had recently prescribed Tylenol with codeine for the patient's severe knee pain 5 days earlier. On examination, the patient was drowsy and falling asleep while practitioners were talking to her. Patient was not cooperative with the physical examination and with a formal mental status examination. Limited examination of the abdomen indicated that it was flat and soft with normal bowel sounds. The patient moves all 4 limbs and plantar is bilateral flexor. Laboratory test results revealed elevated BUN and creatinine levels, and the urine analysis was positive for urinary tract infection. CT scan of the head showed cortical atrophy.
Pathophysiology
Based on the state of arousal, 3 types of delirium are described. Hyperactive delirium is observed in patients in a state of alcohol withdrawal or intoxication with phencyclidine (PCP), amphetamine, and lysergic acid diethylamide (LSD). Hypoactive delirium is observed in patients in states of hepatic encephalopathy and hypercapnia. In mixed delirium, individuals display daytime sedation with nocturnal agitation and behavioral problems.
The mechanism of delirium still is not fully understood. Delirium results from a wide variety of structural or physiological insults. The neuropathogenesis of delirium has been studied in patients with hepatic encephalopathy and alcohol withdrawal. Research in these areas still is limited. The main hypothesis is reversible impairment of cerebral oxidative metabolism and multiple neurotransmitter abnormalities. The following observations support the hypothesis of multiple neurotransmitter abnormalities.
Acetylcholine
Data from animal and clinical studies support the hypothesis that acetylcholine is one of the critical neurotransmitters in the pathogenesis of delirium.1 Clinically, good reasons support this hypothesis. Anticholinergic medications are a well-known cause of acute confusional states, and patients with impaired cholinergic transmission, such those with Alzheimer disease, are particularly susceptible. In patients with postoperative delirium, serum anticholinergic activity is increased.
Dopamine
In the brain, a reciprocal relationship exists between cholinergic and dopaminergic activities. In delirium, an excess of dopaminergic activity occurs. Symptomatic relief occurs with antipsychotic medications such as haloperidol and other neuroleptic dopamine blockers.
Other neurotransmitters
Serotonin: Human and animal studies have found that serotonin is increased in patients with hepatic encephalopathy and septic delirium. Hallucinogens such as LSD act as agonists at the site of serotonin receptors. Serotoninergic agents also can cause delirium.
Gamma-aminobutyric acid (GABA): In patients with hepatic encephalopathy, increased inhibitory GABA levels also are observed. An increase in ammonia levels occurs in patients with hepatic encephalopathy, which causes an increase in the amino acids glutamate and glutamine, which are precursors to GABA. Decreases in CNS GABA levels are observed in patients with delirium resulting from benzodiazepine and alcohol withdrawal.
Cortisol and beta-endorphins: Delirium has been associated with the disruption of cortisol and beta-endorphin circadian rhythms. This mechanism has been suggested as a possible explanation for delirium caused by exogenous glucocorticoids.
Disturbed melatonin disturbance has been associated with sleep disturbances in delirium.2
Inflammatory mechanism
Recent studies have suggested a role for cytokines, such as interleukin-1 and interleukin-6, in the pathogenesis of delirium. Following a wide range of infectious, inflammatory, and toxic insults, endogenous pyrogen, such as interleukin-1, is released from the cells. Head trauma and ischemia, which frequently are associated with delirium, are characterized by brain responses that are mediated by interleukin-1 and interleukin-6.3,4
Stress reaction mechanism
Studies indicate psychosocial stress and sleep deprivation facilitate the onset of delirium.
Structural mechanism
The specific neuronal pathways that cause delirium are unknown. Imaging studies of metabolic (eg, hepatic encephalopathy) and structural (eg, traumatic brain injury, stroke) factors support the hypothesis that certain anatomical pathways may play a more important role than others. The reticular formation and its connections are the main sites of arousal and attention. The dorsal tegmental pathway projecting from the mesencephalic reticular formation to the tectum and the thalamus is involved in delirium.
Disrupted blood-brain barrier can allow neurotoxic agents and inflammatory cytokines to enter the brain and may cause delirium. Contrast-enhanced MRI can be used to assess the blood-brain barrier.5,6
Visuoperceptual deficits in delirium such as hallucinations and delusions are not due to the underlying cognitive impairment.7 Visual hallucinations during alcohol-withdrawal delirium are seen in subjects with polymorphisms of genes coding for dopamine transporter and catechol-O-methyltransferase (COMT).8
Frequency
United States
Delirium is common in the United States. It has been found in 14-56% of elderly patients who are hospitalized. Delirium is present in 10-22% of elderly patients at the time of admission, with an additional 10-30% of cases developing after admission. Delirium has been found in 40% of patients admitted to intensive care units. Prevalence of postoperative delirium following general surgery is 5-10% and as high as 42% following orthopedic surgery. As many as 80% of patients develop delirium near death. Delirium is extremely common among nursing home residents.
Mortality/Morbidity
- In patients who are admitted with delirium, mortality rates are 10-26%.9
- Patients who develop delirium during hospitalization have a mortality rate of 22-76% and a high rate of death during the months following discharge.10
- In patients who are elderly and patients in the postoperative period, delirium may result in a prolonged hospital stay, increased complications, increased cost, and long-term disability.11
Age
Delirium can occur at any age, but it occurs more commonly in patients who are elderly and have compromised mental status. Delirium can occur on top of an underlying dementia. This diagnosis here requires not only a careful mental status but also a thorough history from the patient's family and the staff as well as a comprehensive chart review.
Clinical
History
The diagnosis of delirium is clinical. No laboratory test can diagnose delirium. Obtaining a thorough history is essential.
- Because delirious patients often are confused and unable to provide accurate information, getting a detailed history from family, caregivers, and nursing staff is particularly important. Nursing notes can be very helpful for documentation of episodes of disorientation, abnormal behavior, and hallucinations. Learning to record accurate and specific findings in mental status as well as the particular time the finding was observed is imperative for the staff. Staff should not just report "he was confused."
- Delirium always should be suspected when (a new onset) or an acute or subacute deterioration in behavior, cognition, or function occurs, especially in patients who are elderly, demented, or depressed.
- Patients may have visual hallucinations or persecutory delusions as well as grandiose delusions.
- Some patients with delirium also may become suicidal or homicidal. Therefore, they should not be left unattended or alone.
- Delirium is mistaken for dementia or depression, especially when patients are quiet or withdrawn. However, by Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM-IV-TR) criteria, dementia cannot be diagnosed with certainty when delirium is present. Health professionals can do Mini-Mental Status Exam (MMSE),12 depression assessment screening using DSM-IV-TR criteria,13 or the Geriatric Depression Scale (GDS).14 They can also assess for suicidal and homicidal risk if necessary. Health professionals can directly ask patients about suicidal or homicidal ideation (thoughts), intent, and plan.
- Depression symptoms are commonly seen with delirium. In a recent study, patients having symptoms of dysphoric mood and hopelessness are at risk for incident delirium while in the hospital.15 On the other hand, hypoactive delirium may be mistaken for depression. Up to 42% of patients referred to psychiatry services for suspected depressive illness in the hospital may have delirium.16 Screening for depression in the presence of delirium is quite challenging.
- Delirium is a common cause for psychotic symptoms, bizarre delusions, abnormal behavior, and thought disorders. Agitated patients are at risk for violent and abnormal behavior and in rare circumstances, agitation can lead to attempts of homicide.
- The mental status is a bedside or interview assessment that dramatically fluctuates. It includes the patient's appearance, affect (mood), thoughts (especially the presence of hallucinations and delusions), inquiry into self-destructive behavior, homicidal behavior, judgment and, in this diagnosis, orientation, immediate, recent, and long-term memory.
- Delirium develops in a short period of time (within hours), and an acute change in consciousness or difficulty focusing on what was being said could occur during the interview. Disturbance of the sleep-wake cycle with insomnia, daytime drowsiness, or disturbing dreams or nightmares can also occur. Patients are often unable to remember why they are in the hospital or the events that occurred during the delirious period (for most patients, it is like a blackout period).
- Patients may have false beliefs or thinking (misinterpreting intravenous lines as ropes or snakes) or see or hear things that are not present (picking up things in the air or seeing bugs in the bedclothes). Patients may also misjudge their level of wellness and try to elope from the hospital. Emotional disturbances leading to depression, anxiety, fear, and irritability may be seen in some patients. Delirium in hospitalized seniors may result in the self-removal of catheters or intravenous tubing or attempts to get out of bed, resulting in a fall or injury.
- Main symptoms
- Clouding of consciousness
- Difficulty maintaining or shifting attention
- Disorientation
- Illusions
- Hallucinations
- Fluctuating levels of consciousness
- Symptoms tend to fluctuate over the course of the day, with some improvement in the daytime and maximum disturbance at night. Reversal of the sleep-wake cycle is common.
- Neurological symptoms
- Dysphasia
- Dysarthria
- Tremor
- Asterixis in hepatic encephalopathy and uremia
- Motor abnormalities
- Patients with delirium who are hyperactive have an increased state of arousal, psychomotor abnormalities, and hypervigilance. In contrast, patients with delirium who are hypoactive are withdrawn, less active, and sleepy.
- Hypoactive delirium sometimes is misdiagnosed as dementia or depression.
- In patients who are elderly, delirium often is the presenting symptom of an underlying illness.
- Subsyndromal delirium has been defined as the presence of some core diagnostic symptoms that do not meet the criteria for diagnostic threshold. Prevalence rates of 30-50% have been reported in intensive care units.17,18
- A prodromal phase lasting for hours to days can occur before full syndromal delirium becomes evident. This includes sleep disturbances, vivid dreams, frequent calls for assistance, and anxiety.17,18
Physical
- A careful and complete physical examination including a mental status examination is necessary. Testing vital signs such as temperature, pulse, blood pressure, and respiration is mandatory.
- Patients have difficulty sustaining attention, problems in orientation and short-term memory, poor insight, and impaired judgment. Key elements here are fluctuating levels of consciousness.
- Impaired attention can be assessed with bedside tests that require sustained attention to a task that has not been memorized, such as reciting the days of the week or months of the year backwards, counting backwards from 20, or doing serial subtraction.
- DSM-IV-TR diagnostic criteria for delirium13
- Disturbance of consciousness (ie, reduced clarity of awareness of the environment) occurs, with reduced ability to focus, sustain, or shift attention.
- Change in cognition (eg, memory deficit, disorientation, language disturbance, perceptual disturbance) occurs that is not better accounted for by a preexisting, established, or evolving dementia.
- The disturbance develops over a short period (usually hours to days) and tends to fluctuate during the course of the day.
- Evidence from the history, physical examination, or laboratory findings is present that indicates the disturbance is caused by a direct physiologic consequence of a general medical condition, an intoxicating substance, medication use, or more than one cause.
- Other diagnostic instruments are the Delirium Symptom Interview (DSI) and the Confusion Assessment Method (CAM).19
- Delirium symptom severity can be assessed by the Delirium Rating Scale (DRS) and the Memorial Delirium Assessment Scale (MDAS).
- Table 1. Differentiating Features of Delirium and Dementia
Open table in new window
[ CLOSE WINDOW ]Table
Features Delirium Dementia Onset Acute Insidious Course Fluctuating Progressive Duration Days to weeks Months to years Consciousness Altered Clear Attention Impaired Normal, except in severe dementia Psychomotor changes Increased or decreased Often normal Reversibility Usually Rarely Features Delirium Dementia Onset Acute Insidious Course Fluctuating Progressive Duration Days to weeks Months to years Consciousness Altered Clear Attention Impaired Normal, except in severe dementia Psychomotor changes Increased or decreased Often normal Reversibility Usually Rarely - To make an accurate diagnosis, periodic application of diagnostic criteria such as CAM or DSM-IV criteria and knowledge of the patient's baseline mental status is imperative.
- A simple cognitive test like the Mini-Cog can be a predictor of inhospital delirium. At the time of admission to the hospital, if the elderly patient does not have a history of dementia or cognitive impairment, the Mini-Cog can be used to identify patients at high risk for inhospital delirium.
- The Confusion Assessment Method for the Intensive Care Unit (CAM-ICU) offers the clinician the opportunity to identify delirium in critical care patients, especially patients on mechanical ventilation. The CAM-ICU makes use of nonverbal assessments to evaluate the important features of delirium.
- Another instrument that can be used in ICU settings is the Intensive Care Delirium Screening Checklist (ICDSC). The severity of delirium in the ICU can be estimated by the Delirium Detection Scale (DDS).
Causes
Almost any medical illness, intoxication, or medication can cause delirium. Often, delirium is multifactorial in etiology, and the physician treating the delirium should investigate each cause contributing to it. Medications are the most common reversible cause of delirium.
- DSM-IV-TR classification of delirium
- Delirium due to general medical condition
- Substance intoxication delirium
- Substance withdrawal delirium
- Delirium due to multiple etiologies
- Delirium not otherwise specified
- Some of the other common reversible causes include the following:
- Hypoxia
- Hypoglycemia
- Hyperthermia
- Anticholinergic delirium
- Alcohol or sedative withdrawal
- Other causes of delirium include the following:
- Infections
- Metabolic abnormalities
- Structural lesions of the brain
- Postoperative states
- Miscellaneous causes, such as sensory deprivation, sleep deprivation, fecal impaction, urinary retention, and change of environment
- In persons who are elderly, medications at therapeutic doses and levels can cause delirium.
- Although numerous risk factors have been described, a recent study identified 5 important independent risk factors.
- Use of physical restraints
- Malnutrition
- Use of a bladder catheter
- Any iatrogenic event
- Use of 3 or more medications
- Dementia is one of the strongest most consistent risk factors. Underlying dementia is observed in 25-50% of patients. The presence of dementia increases the risk of delirium 2-3 times. Low educational level, which may be an indicator of low cognitive reserve, is associated with increased vulnerability to delirium.
- Dysphoric mood and hopelessness are also risk factors for incident delirium.
- Structural changes
- Closed head injury or cerebral hemorrhage
- Cerebrovascular accidents, such as cerebral infarction, subarachnoid hemorrhage, and hypertensive encephalopathy
- Primary or metastatic brain tumors
- Brain abscess
- Metabolic causes
- Fluid and electrolyte abnormalities, acid-base disturbances, and hypoxia
- Hypoglycemia
- Hepatic or renal failure
- Vitamin deficiency states (especially thiamine and cyanocobalamin)
- Endocrinopathies associated with the thyroid and parathyroid
- Hypoperfusion states
- Shock
- Congestive heart failure
- Cardiac arrhythmias
- Anemias
- Infectious causes
- CNS infections such as meningitis
- Encephalitis
- HIV-related brain infections
- Septicemia
- Pneumonia
- Urinary tract infections
- Toxic causes
- Substance intoxication - Alcohol, heroin, cannabis, PCP, and LSD
- Medication-induced delirium
- Anticholinergics (Benadryl, tricyclic antidepressants)
- Narcotics (meperidine)
- Sedative hypnotics (benzodiazepines)
- Histamine-2 (H2) blockers (cimetidine)
- Corticosteroids
- Centrally acting antihypertensives (methyldopa, reserpine)
- Anti-Parkinson drugs (levodopa)
- Substance withdrawal from alcohol, opioids, and benzodiazepines
- Other causes
- Postictal state
- Unfamiliar environment
- Operation-related delirium
- Preoperative (dementia, polypharmacy, fluid and electrolyte imbalance)
- Intraoperative (meperidine, long-acting benzodiazepines, anticholinergics such as atropine; however, medications such as glycopyrrolate can be used because, in contrast to atropine, they do not cross the blood brain barrier)
- Postoperative (hypoxia, hypotension, drug withdrawal)
- Mild cognitive impairment and vascular risk factors can be independent risk factors for postoperative delirium.20
- Drugs are a common risk factor for delirium, and drug-induced delirium is commonly seen in medical practice, especially in hospital settings. The risk of anticholinergic toxicity is greater in elderly persons, and the risk of inducing delirium by medications is high in frail, elderly persons and in those with dementia.
More on Delirium |
 Overview: Delirium |
| Differential Diagnoses & Workup: Delirium |
| Treatment & Medication: Delirium |
| Follow-up: Delirium |
| References |
| Next Page » |
References
White S. The neuropathogenesis of delirium. Rev Clin Gerontol. 2002;12:62-67.
Shigeta H, Yasui A, Nimura Y, et al. Postoperative delirium and melatonin levels in elderly patients. Am J Surg. Nov 2001;182(5):449-54. [Medline].
de Rooij SE, van Munster BC, Korevaar JC, Levi M. Cytokines and acute phase response in delirium. J Psychosom Res. May 2007;62(5):521-5. [Medline].
Rudolph JL, Ramlawi B, Kuchel GA, et al. Chemokines are associated with delirium after cardiac surgery. J Gerontol A Biol Sci Med Sci. Feb 2008;63(2):184-9. [Medline].
Ebersoldt M, Sharshar T, Annane D. Sepsis-associated delirium. Intensive Care Med. Jun 2007;33(6):941-50. [Medline].
Banks WH. The aged blood- brain barrier: A substrate for CNS disease. Facts, Research and Intervention in Geriatrics. 2000;2000(2):521-530.
Brown LJ, McGrory S, McLaren L, Starr JM, Deary IJ, Maclullich AM. Cognitive visual perceptual deficits in patients with delirium. J Neurol Neurosurg Psychiatry. Jun 2009;80(6):594-9. [Medline].
Limosin F, Loze JY, Boni C, et al. The A9 allele of the dopamine transporter gene increases the risk of visual hallucinations during alcohol withdrawal in alcohol-dependent women. Neurosci Lett. May 20 2004;362(2):91-4. [Medline].
McCusker J, Cole M, Abrahamowicz M, Primeau F, Belzile E. Delirium predicts 12-month mortality. Arch Intern Med. Feb 25 2002;162(4):457-63. [Medline].
American Psychiatric Association. Practice guideline for the treatment of patients with delirium. Am J Psychiatry. May 1999;156(5 Suppl):1-20. [Medline].
Marcantonio ER, Kiely DK, Simon SE, et al. Outcomes of older people admitted to postacute facilities with delirium. J Am Geriatr Soc. Jun 2005;53(6):963-9. [Medline].
Folstein MF, Folstein SE, McGugh PR. "Mini- Mental State".A practical method for grading the cognitive state of patients for the clinician. J Psychiatr Res. Nov. 1975;12(3):189-98.
American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR). 4th ed. Washington, DC: American Psychiatric Association; 2000.
Yesavage JA, Brink TL, Rose TL, et al. Development and validation of a geriatric depression screening scale: a preliminary report. J Psychiatr Res. Apr 1983;17:37-49.
McAvay GJ, Van Ness PH, Bogardus ST Jr, Zhang Y, Leslie DL, Leo-Summers LS. Depressive symptoms and the risk of incident delirium in older hospitalized adults. J Am Geriatr Soc. May 2007;55(5):684-91. [Medline].
Farrell KR, Ganzini L. Misdiagnosing delirium as depression in medically ill elderly patients. Arch Intern Med. Dec 11-25 1995;155(22):2459-64. [Medline].
Cole M, McCusker J, Dendukuri N, Han L. The prognostic significance of subsyndromal delirium in elderly medical inpatients. J Am Geriatr Soc. Jun 2003;51(6):754-60. [Medline].
Ouimet S, Riker R, Bergeron N, Cossette M, Kavanagh B, Skrobik Y. Subsyndromal delirium in the ICU: evidence for a disease spectrum. Intensive Care Med. Jun 2007;33(6):1007-13. [Medline].
Inouye SK, van Dyck CH, Alessi CA. Clarifying confusion: the confusion assessment method. A new method for detection of delirium. Ann Intern Med. Dec 15 1990;113(12):941-8. [Medline].
Rudolph JL, Jones RN, Rasmussen LS, Silverstein JH, Inouye SK, Marcantonio ER. Independent vascular and cognitive risk factors for postoperative delirium. Am J Med. Sep 2007;120(9):807-13. [Medline].
Perry SW. Organic mental disorders caused by HIV: update on early diagnosis and treatment. Am J Psychiatry. Jun 1990;147(6):696-710. [Medline].
Overshott R, Karim S, Burns A. Cholinesterase inhibitors for delirium. Cochrane Database Syst Rev. Jan 23 2008;CD005317. [Medline].
Alagiakrishnan K, Marrie T, Rolfson D, Coke W, Camicioli R, Duggan D. Simple cognitive testing (Mini-Cog) predicts in-hospital delirium in the elderly. J Am Geriatr Soc. Feb 2007;55(2):314-6. [Medline].
Alagiakrishnan K, Wiens CA. An approach to drug induced delirium in the elderly. Postgrad Med J. Jul 2004;80(945):388-93. [Medline].
Alsop DC, Fearing MA, Johnson K, Sperling R, Fong TG, Inouye SK. The role of neuroimaging in elucidating delirium pathophysiology. J Gerontol A Biol Sci Med Sci. Dec 2006;61(12):1287-93. [Medline].
Bergeron N, Dubois MJ, Dumont M, Dial S, Skrobik Y. Intensive Care Delirium Screening Checklist: evaluation of a new screening tool. Intensive Care Med. 2001;27:859-864.
Chan D, Brennan NJ. Delirium: making the diagnosis, improving the prognosis. Geriatrics. Mar 1999;54(3):28-30, 36, 39-42. [Medline].
Day JJ, Bayer AJ, McMahon M. Thiamine status, vitamin supplements and postoperative confusion. Age Ageing. Jan 1988;17(1):29-34. [Medline].
Ely EW, Inouye SK, Bernard GR. Delirium in mechanically ventilated patients: validity and reliability of the confusion assessment method for the intensive care unit (CAM-ICU). JAMA. Dec 5 2001;286(21):2703-10. [Medline].
Hung OL, Lewin NA, Howland MA. Herbal preparations. In: Goldfrank LR, Flomenbaum NE, Lewin NA, et al, eds. Goldfrank's Toxicologic Emergencies. 7th ed. New York: McGraw-Hill; 2002:1129.
Inouye SK. The dilemma of delirium: clinical and research controversies regarding diagnosis and evaluation of delirium in hospitalized elderly medical patients. Am J Med. Sep 1994;97(3):278-88. [Medline].
Inouye SK, Bogardus ST, Charpentier PA, et al. A multicomponent intervention to prevent delirium in hospitalized older patients. N Engl J Med. Mar 4 1999;340(9):669-76. [Medline].
Inouye SK, Charpentier PA. Precipitating factors for delirium in hospitalized elderly persons. Predictive model and interrelationship with baseline vulnerability. JAMA. Mar 20 1996;275(11):852-7. [Medline].
Jones RN, Yang FM, Zhang Y, Kiely DK, Marcantonio ER, Inouye SK. Does educational attainment contribute to risk for delirium? A potential role for cognitive reserve. J Gerontol A Biol Sci Med Sci. Dec 2006;61(12):1307-11. [Medline].
[Best Evidence] Leslie DL, Zhang Y, Holford TR, Bogardus ST, Leo- Summers LS, Inouye SK. Premature death associated with delirium at 1-year follow-up. Arch Intern Med. July 2005;165(14):1657-62. [Medline].
Lipowski ZJ. Delirium (acute confusional states). JAMA. Oct 2 1987;258(13):1789-92. [Medline].
Lipowski ZJ. Delirium in the elderly patient. N Engl J Med. Mar 2 1989;320(9):578-82. [Medline].
Liptzin B, Levkoff SE. An empirical study of delirium subtypes. Br J Psychiatry. Dec 1992;161:843-5. [Medline].
Liptzin B, Levkoff SE, Gottlieb GL. Delirium. J Neuropsychiatry Clin Neurosci. Spring 1993;5(2):154-60. [Medline].
McAvay GJ, Van Ness PH, Bogardus ST Jr, Zhang Y, Leslie DL, Leo-Summers LS. Depressive symptoms and the risk of incident delirium in older hospitalized adults. J Am Geriatr Soc. May 2007;55(5):684-91. [Medline].
O'Keeffee ST. Delirium in the elderly. Age Ageing. Sep 1999;28 Suppl 2:5-8. [Medline].
O'Keeffe ST, Ni Chonchubhair A. Postoperative delirium in the elderly. Br J Anaesth. Nov 1994;73(5):673-87. [Medline].
Obrecht R, Okhomina FO, Scott DF. Value of EEG in acute confusional states. J Neurol Neurosurg Psychiatry. Jan 1979;42(1):75-7. [Medline].
Otter H, Martin J, Bäsell K, von Heymann C, Hein OV, Böllert P. Validity and reliability of the DDS for severity of delirium in the ICU. Neurocrit Care. 2005;2(2):150-8. [Medline].
Ouimet S, Riker R, Bergeon N, Cosette M, Kavanagh B, Skrobik Y. Subsyndromal delirium in the ICU: evidence for a disease spectrum. Intensive Care Med. Apr 3 2007;33(6):1007-1013. [Medline].
Sipahimalani A, Masand PS. Use of risperidone in delirium: case reports. Ann Clin Psychiatry. Jun 1997;9(2):105-7. [Medline].
Trzepacz PT. Delirium. Advances in diagnosis, pathophysiology, and treatment. Psychiatr Clin North Am. Sep 1996;19(3):429-48. [Medline].
Further Reading
Keywords
acute confusional state, acute cognitive dysfunction, toxic metabolic encephalopathy, hyperactive delirium, hypoactive delirium, mixed delirium
