Definition and epidemiology
Delirium is a neuropsychiatric syndrome defined by an acute change in attention, awareness, and cognition that develops over hours to days and tends to fluctuate in severity throughout the day. It is a direct physiological consequence of an underlying medical illness, intoxication, withdrawal, medication effect, or multifactorial insult, rather than a primary psychiatric disorder.
- Affects up to 10-30% of hospitalized general medical patients and up to 50-80% of ICU patients, especially those who are mechanically ventilated
- Occurs in 15-25% of patients after major surgery, with rates up to 50% after hip fracture repair or cardiac surgery
- Prevalence increases sharply with age; delirium is uncommon in healthy young adults without a precipitating insult (toxic/metabolic, drug-induced, or severe illness)
- Underrecognized and underdiagnosed, particularly the hypoactive subtype, which is often mistaken for depression or fatigue
- Associated with increased length of stay, mortality, institutionalization, and long-term cognitive decline
- Acute onset and fluctuating course distinguish delirium from dementia
- Inattention is the core diagnostic feature, not just confusion
- Hypoactive delirium is the most commonly missed subtype
- CAM (Confusion Assessment Method) is the standard bedside diagnostic tool
- Cholinergic deficiency and dopaminergic excess are the key proposed mechanisms
- Always check glucose, oxygenation, and medication list first in any acutely confused patient
- Nonpharmacologic measures are first-line; antipsychotics are reserved for severe agitation
- Avoid benzodiazepines except in alcohol or benzodiazepine withdrawal delirium
Etiology and risk factors
Delirium is almost always multifactorial, resulting from the interaction between an underlying vulnerability (predisposing factors) and an acute insult (precipitating factors).
Predisposing factors
- Advanced age
- Pre-existing dementia or cognitive impairment
- Multiple comorbidities, frailty
- Sensory impairment (vision, hearing)
- Prior stroke or brain injury
- Depression
Precipitating factors (common exam causes)
- Infection: urinary tract infection, pneumonia, sepsis
- Metabolic derangement: hypoglycemia, hyponatremia, hypercalcemia, uremia, hepatic encephalopathy
- Drugs: anticholinergics, benzodiazepines, opioids, corticosteroids, polypharmacy
- Substance intoxication or withdrawal: alcohol withdrawal, benzodiazepine withdrawal
- Hypoxia, hypercapnia
- Post-operative state, especially after hip or cardiac surgery
- Urinary retention or fecal impaction (common in elderly inpatients)
- Pain, immobilization, sleep deprivation, ICU environment
- Primary CNS causes: stroke, meningitis, encephalitis, seizure (postictal state), traumatic brain injury
A simple mnemonic for common precipitants is DELIRIUM, used widely for exam recall (see mnemonic section).
Pathophysiology
The pathophysiology is not fully understood but is thought to involve a final common pathway of widespread cortical and subcortical dysfunction from multiple converging mechanisms.
- Neurotransmitter imbalance: relative cholinergic deficiency and dopaminergic excess are the most supported mechanisms; this explains why anticholinergic drugs precipitate delirium and antidopaminergic agents can reduce agitation
- Neuroinflammation: systemic inflammation (sepsis, surgery) triggers cytokine release (IL-6, TNF-alpha) that disrupts the blood-brain barrier and neuronal signaling
- Impaired oxidative metabolism: hypoxia, hypoglycemia, and reduced cerebral blood flow impair neuronal energy supply
- Network disruption: functional imaging shows disrupted connectivity in attention and arousal networks, particularly involving the thalamus, prefrontal cortex, and reticular activating system
- Aging brain and neurodegenerative disease reduce cognitive reserve, lowering the threshold at which any of the above insults produce clinical delirium
Clinical features
The hallmark is acute onset with a fluctuating course, inattention, and disorganized thinking, often with disturbance of the sleep-wake cycle.
Core features
- Acute onset (hours to days), fluctuating throughout the day, often worse at night ("sundowning")
- Inattention: difficulty focusing, sustaining, or shifting attention
- Disorganized thinking: rambling or incoherent speech
- Altered level of consciousness: ranges from hypervigilant to lethargic or stuporous
- Perceptual disturbances: illusions, hallucinations (often visual), delusions (usually poorly formed and transient)
- Disorientation to time and place
- Memory impairment, particularly short-term
Clinical subtypes
| Subtype | Features |
|---|---|
| Hyperactive | Agitation, restlessness, hallucinations, autonomic hyperactivity; most easily recognized |
| Hypoactive | Lethargy, withdrawal, reduced activity; often missed, mistaken for depression; worse prognosis |
| Mixed | Fluctuates between hyperactive and hypoactive features; most common subtype |
Diagnosis
Delirium is a clinical diagnosis based on bedside cognitive assessment and history of acute change, supported by a workup to identify the underlying cause.
DSM-5 criteria (core concept)
- Disturbance in attention and awareness
- Develops acutely and fluctuates in severity
- Additional disturbance in cognition (memory, disorientation, language, visuospatial, or perception)
- Not better explained by a pre-existing or evolving neurocognitive disorder
- Evidence that the disturbance is a direct physiological consequence of a medical condition, intoxication, withdrawal, or medication
Bedside tools
- Confusion Assessment Method (CAM): most widely used; requires acute onset/fluctuating course AND inattention, plus either disorganized thinking OR altered consciousness
- CAM-ICU: adapted version for nonverbal, mechanically ventilated patients
- 4AT: rapid 4-item screening tool used in many hospitals
- Collateral history from family or nursing staff is essential to establish the patient's baseline cognition and timeline of change
Workup to find the cause
- Vital signs, pulse oximetry, fingerstick glucose
- Complete blood count, metabolic panel, calcium, liver function tests, renal function
- Urinalysis and urine culture
- Review of all medications, including recent additions and withdrawals
- Blood cultures and chest imaging if infection suspected
- Arterial blood gas if hypoxia or hypercapnia suspected
- Neuroimaging (CT/MRI brain) and lumbar puncture reserved for focal neurologic signs, head trauma, fever with meningeal signs, or unexplained cases
- EEG if seizure or nonconvulsive status epilepticus is suspected
Differential diagnosis
- Dementia: gradual onset, stable attention early in disease, no fluctuation over hours; delirium and dementia frequently coexist and dementia is the strongest risk factor for delirium
- Depression: can mimic hypoactive delirium with withdrawal and slowed thinking, but attention and level of consciousness are typically preserved
- Primary psychotic disorder (schizophrenia): hallucinations tend to be auditory and well-organized; onset is not acute in a previously well patient, and consciousness is clear
- Nonconvulsive status epilepticus: persistent altered consciousness without obvious seizure activity; diagnosed with EEG
- Wernicke encephalopathy: confusion plus ophthalmoplegia and ataxia in a patient with alcohol use disorder or malnutrition
- Catatonia: can feature stupor or agitation but with characteristic motor features (posturing, waxy flexibility, mutism)
Management
Management prioritizes identifying and treating the underlying cause, with nonpharmacologic strategies as first-line for prevention and symptom control; antipsychotics are reserved for severe agitation that threatens safety or interferes with essential care.
Treat the underlying cause
- Correct metabolic abnormalities, treat infections, discontinue or adjust offending medications
- Manage withdrawal syndromes appropriately (benzodiazepines for alcohol/benzodiazepine withdrawal specifically)
- Optimize oxygenation, hydration, and nutrition
Nonpharmacologic measures (first-line, strongest evidence for prevention)
- Frequent reorientation; clocks, calendars, familiar objects and faces
- Correct sensory deficits: provide glasses and hearing aids
- Promote normal sleep-wake cycle: daytime light exposure, minimize nighttime noise and interruptions
- Early mobilization, avoid unnecessary catheters and restraints
- Ensure adequate hydration and nutrition
- Review and minimize deliriogenic medications (anticholinergics, benzodiazepines, opioids where possible)
- Multicomponent protocols (e.g., Hospital Elder Life Program-type approaches) reduce incidence in at-risk inpatients
Pharmacologic management
- Avoid routine sedative or antipsychotic use; reserve for severe agitation causing risk to patient or staff safety, or distressing psychotic symptoms, when nonpharmacologic measures fail
- Low-dose haloperidol or atypical antipsychotics (risperidone, olanzapine, quetiapine) are used short-term when pharmacologic treatment is needed
- Avoid antipsychotics in Parkinson disease and Lewy body dementia; use with caution and ECG monitoring if QT prolongation risk
- Benzodiazepines are generally avoided except for alcohol/benzodiazepine withdrawal delirium, where they are first-line
- Guideline note: major societies (American Geriatrics Society, UK NICE, Society of Critical Care Medicine) converge on nonpharmacologic prevention as the standard of care and discourage routine antipsychotic use; they differ slightly on thresholds for pharmacologic rescue therapy in refractory agitation
Complications and prognosis
- Increased in-hospital mortality and 1-year mortality compared with matched patients without delirium
- Prolonged hospital length of stay and increased risk of nosocomial complications (falls, pressure injuries, aspiration, catheter-associated infections)
- Increased risk of institutionalization (nursing home placement) after discharge
- Associated with accelerated long-term cognitive decline and increased risk of incident dementia
- Most cases resolve within days to weeks once the underlying cause is treated, but resolution can take longer in older adults or those with pre-existing dementia
- Some patients, particularly the elderly, never return to their prior cognitive baseline
DELIRIUMS: Drugs, Eyes/ears (sensory impairment), Low O2 (hypoxia, MI, PE), Infection, Retention (urine/stool), Ictal (seizure), Underhydration/undernutrition, Metabolic (electrolytes, glucose, thyroid), Subdural/structural CNS lesion
Practice questions
1. An 82-year-old woman is hospitalized for a hip fracture repair. On postoperative day 2, she becomes agitated, pulls at her IV lines, and is disoriented to place and time. Her daughter reports she was fully oriented and conversant before surgery. Vital signs are notable for a temperature of 38.3°C. Which of the following is the most appropriate next step?
2. A 70-year-old man with Parkinson disease is admitted for pneumonia. On hospital day 3, he develops visual hallucinations, agitation, and worsening confusion that fluctuates throughout the day. Which medication class should be avoided in managing his agitation?
3. A 65-year-old man with chronic alcohol use disorder is admitted after a motor vehicle collision. On hospital day 2, he becomes tremulous, diaphoretic, tachycardic, and acutely confused with visual hallucinations. Which medication class is first-line for this patient's agitation?
Frequently asked questions
What causes delirium?
Delirium is caused by an acute medical insult acting on a vulnerable brain, most commonly infection, metabolic disturbance, medication side effects, drug or alcohol withdrawal, surgery, or hypoxia. It is rarely due to a single cause; in hospitalized elderly patients it is usually multifactorial, combining predisposing factors like dementia or frailty with a precipitating illness or drug exposure.
What are the first symptoms of delirium?
The first symptoms are usually a sudden change in attention and alertness, such as difficulty following conversation, disorientation to time or place, and a fluctuating level of awareness that can worsen at night. Family or nursing staff often notice the change before clinicians do, since it represents a departure from the patient's usual baseline.
How is delirium diagnosed?
Delirium is diagnosed clinically using bedside tools like the Confusion Assessment Method, which looks for acute onset, fluctuating course, inattention, and either disorganized thinking or altered consciousness. Diagnosis also requires a collateral history to confirm the change is acute, plus a focused workup (labs, infection screen, medication review) to identify the underlying cause.
Is delirium curable?
Yes, delirium is usually reversible once the underlying cause is identified and treated, with most patients recovering within days to a few weeks. However, recovery can be slower or incomplete in older adults, those with pre-existing dementia, or when the underlying illness is severe, and some patients do not fully return to their prior cognitive baseline.
Delirium vs dementia, what is the difference?
Delirium has an acute onset and fluctuating course over hours to days with impaired attention, while dementia develops gradually over months to years with relatively preserved attention until late stages. Delirium is usually reversible with treatment of the underlying cause, whereas dementia is typically a chronic, progressive condition; the two frequently coexist, and dementia is the strongest risk factor for developing delirium.
Key drugs
Related conditions and differentials
Sources and further reading
StatPearls (NCBI Bookshelf)MedlinePlusWHO ICD-10: F05
Educational content for medical students, prepared by the WhiteCoat Pro editorial team with AI assistance; every page is reviewed by a second AI model for factual errors. It is not medical advice and does not replace the product label, local guidelines or a clinician.