Delirium Clinical Presentation

Updated: Apr 25, 2019
  • Author: Kannayiram Alagiakrishnan, MD, MBBS, MPH, MHA; Chief Editor: Glen L Xiong, MD  more...
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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Delirium is mistaken for dementia or depression, especially when patients are quiet or withdrawn.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, Fifth Edition (DSM5) criteria, dementia cannot be diagnosed with certainty when delirium is present. Health professionals can do Mini-Mental Status Exam (MMSE), [20] depression assessment screening using DSM-5 criteria, [1] or the Geriatric Depression Scale (GDS). [21] 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. [22] 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. [23] 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.

The main symptoms of delirium include the following:

  • 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 may include the following:

  • 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. [24, 25]

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. [24, 25]



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-5 diagnostic criteria for delirium [1] is as follows:

  • 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). [26]

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 a new window)











Days to weeks

Months to years






Normal, except in severe dementia

Psychomotor changes

Increased or decreased

Often normal




To make an accurate diagnosis, periodic application of diagnostic criteria such as CAM or DSM5 criteria and knowledge of the patient's baseline mental status is imperative.

Gaps in the medical record such as once daily cognitive assessment or no formal assessments on the hallmarks of delirium (attention span and fluctuation) may make diagnosing the condition more difficult.  The physicians depend on health records (nursing notes) to identify a fluctuating course. The type of information might also be less than adequate for developing a timely diagnosis. So the recognition of delirium can be delayed by infrequent observation or documentation. [27]

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).

A 2012 meta-analysis showed a sensitivity of 75.5% and specificity of 95.8% for CAM-ICU, whereas sensitivity and specificity for the ICDSC were 80.1% and 74.6%, respectively. These results suggest the CAM-ICU is one of the most specific bedside tests that can be used to diagnose delirium in ICU patients. [28]

The CAM-S was developed for measuring the severity of delirium in hospitalized patients (short form) and those in research settings (long form). [29, 30]  Developers reported good psychometric properties, high interrater reliability, and strong associations with important clinical outcomes with this tool, which is based on the standardized and validated Confusion Assessment Method (CAM) that screens for the presence—but not the severity—of delirium. The CAM-S was tested in 2 independent cohorts at 3 academic centers comprising 300 patients scheduled for major surgery and 919 medical patients (all patients aged ≥70 y). [29, 30]



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.

Some of the other common reversible causes include the following:

  • Hypoxia

  • 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 that may contribute to delirium include the following:

Metabolic causes may include the following:

  • 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 such as shock congestive heart failure, cardiac arrhythmias, and anemias may contribute to delirium.

Infectious causes may include the following:

Substance intoxication  with alcohol, heroin, cannabis, PCP, and LSD may cause symptoms of delirium. Withdrawal from these substances may also contribute.

Medication-induced delirium can be caused by any of the following agents:

  • Anticholinergics (Benadryl, tricyclic antidepressants)

  • Narcotics (meperidine)

  • Sedative hypnotics (benzodiazepines)

  • Histamine-2 (H2) blockers (cimetidine)

  • Corticosteroids

  • Centrally acting antihypertensives (methyldopa, reserpine)

  • Anti-Parkinson drugs (levodopa)

Other causes may include postictal state and unfamiliar environment.

Delirium may come about as a result of surgery or operation.

  • 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. [31]

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.