Delirium is an acute, fluctuating disturbance of attention and awareness with disorganized thinking, caused by an underlying medical condition, substance, or medication effect. It is one of the most common and most lethal syndromes encountered on medical and surgical wards, complicating roughly one in five general hospital admissions and the majority of ICU stays, yet it is missed in clinical practice as often as half the time, particularly in its hypoactive form. DSM-5-TR classifies delirium under neurocognitive disorders, distinguishing it from dementia primarily by its acute onset, fluctuating course, and prominent inattention. The headline clinical move is twofold: identify and treat the underlying cause, and protect the brain with multicomponent non-pharmacologic care (orientation, mobilization, sleep, sensory aids, hydration), reserving antipsychotics for severe agitation that threatens safety or essential treatment. Benzodiazepines are harmful in delirium except when the cause is alcohol or sedative-hypnotic withdrawal. Delirium is not a benign transient state — it independently predicts in-hospital mortality, prolonged hospitalization, persistent cognitive impairment, and new institutionalization.

Delirium is common, under-recognized, and disproportionately a disease of the old and the critically ill. Hospital settings drive most of the burden.

Prevalence and incidence

• Overall point prevalence in general hospital inpatients is approximately 23%, with higher rates in older adults and surgical populations.^[1]
• ICU incidence ranges from 20% to 80% depending on illness severity and mechanical ventilation status, with mechanically ventilated patients at the high end.^[2]
• Postoperative delirium occurs in 15-25% of older adults after major elective surgery and in 50% or more after hip fracture repair or cardiac surgery.^[3]
• Up to half of all delirium episodes are missed at the bedside, particularly hypoactive presentations.^[1]

Demographics and risk factors

• Age over 65 is the strongest demographic risk factor; prevalence rises steeply across each subsequent decade.^[1]
• Pre-existing cognitive impairment (dementia or mild cognitive impairment) increases risk roughly 2- to 5-fold.^[4]
• Other predisposing factors include frailty, multimorbidity, functional dependence, sensory impairment (vision, hearing), prior delirium, depression, and chronic alcohol use.^[4]
• Precipitating factors include acute infection, surgery, hypoxia, metabolic derangement, dehydration, urinary retention, fecal impaction, uncontrolled pain, sleep deprivation, restraints, bladder catheterization, and high-risk medications.^[4]

Comorbidity and outcomes

• Delirium is independently associated with in-hospital mortality (odds ratio approximately 1.5-2.0) after adjustment for severity of illness.^[5]
• One-year mortality after an episode is roughly 35-40% in older medical inpatients.^[5]
• Delirium superimposed on dementia accelerates long-term cognitive decline and increases risk of new nursing home placement.^[6]

Delirium is best understood as acute brain failure: a final common pathway by which systemic insults destabilize cortical and subcortical networks that subserve attention and arousal. No single neurotransmitter or lesion explains every case, but several converging mechanisms recur.

Neurotransmitter hypotheses

• Cholinergic deficiency is the most replicated finding; anticholinergic medications precipitate delirium, and serum anticholinergic activity correlates with severity.^[7]
• Dopaminergic excess relative to acetylcholine is invoked to explain why dopamine antagonists can blunt agitation and perceptual disturbance.^[7]
• GABAergic excess (sedatives, hepatic encephalopathy) and glutamatergic dysregulation contribute, particularly in hypoactive and withdrawal-related presentations.^[7]
• Serotonergic, noradrenergic (especially in alcohol withdrawal), and melatonergic disturbances modulate the sleep-wake disruption that is nearly universal.^[7]

Neuroinflammation and systemic stress

• Peripheral inflammation (sepsis, surgery) drives microglial activation and blood-brain barrier permeability, releasing cytokines (IL-6, TNF-alpha, IL-1beta) that disrupt neuronal signaling.^[8]
• Hypothalamic-pituitary-adrenal axis activation produces sustained cortisol elevation, which is neurotoxic to hippocampal and prefrontal circuits.^[8]
• Cerebral hypoperfusion, hypoxia, and metabolic derangement (hyponatremia, hypoglycemia, hypercalcemia, uremia) provide direct neuronal insults.^[8]

Network-level findings

• Functional imaging during delirium shows disrupted connectivity of the default mode network and impaired top-down attentional control by frontoparietal networks.^[9]
• EEG typically shows generalized slowing with increased theta and delta power; this finding is sensitive and helps distinguish delirium from primary psychiatric illness.^[9]

Genetic and predisposition factors

• APOE epsilon-4 carriage has been inconsistently associated with postoperative delirium risk.^[10]
• The dominant predisposition signal remains brain vulnerability (pre-existing dementia, prior stroke, white matter disease) rather than a specific allele.^[10]

The DSM-5-TR criteria operationalize delirium as an acute, fluctuating disturbance of attention and awareness with an identifiable medical cause. Bedside recognition hinges on attention, not orientation.

DSM-5-TR core criteria

• A disturbance of attention (reduced ability to direct, focus, sustain, and shift attention) and of awareness (reduced orientation to the environment).^[11]
• The disturbance develops over a short period (hours to days), represents an acute change from baseline, and tends to fluctuate in severity during the course of a day.^[11]
• An additional cognitive disturbance (memory, disorientation, language, visuospatial ability, or perception) is present.^[11]
• The disturbances are not better explained by a pre-existing, established, or evolving neurocognitive disorder and do not occur in the context of a severely reduced level of arousal such as coma.^[11]
• There is evidence from history, examination, or laboratory findings that the disturbance is a direct physiological consequence of another medical condition, substance intoxication or withdrawal, a toxin, or multiple etiologies.^[11]

Subtypes (etiologic specifiers)

• Substance intoxication delirium, substance withdrawal delirium, medication-induced delirium, delirium due to another medical condition, and delirium due to multiple etiologies.^[11]

Course and motor specifiers

• Acute (hours to days) or persistent (weeks to months).^[11]
• Hyperactive: heightened psychomotor activity, mood lability, refusal to cooperate.^[11]
• Hypoactive: reduced psychomotor activity, sluggishness approaching stupor; commonly missed and associated with worse prognosis.^[11]
• Mixed level of activity, or normal psychomotor activity with attention and awareness disturbance.^[11]

ICD-11 differences

• ICD-11 retains essentially the same construct and uses the term "delirium" within the neurocognitive disorders grouping; criteria are operationally similar to DSM-5-TR, with slightly more permissive language around evidence of etiology.^[12]

The classic bedside picture is a patient whose mental status changed overnight, who cannot hold a conversation, and whose family says "this is not him." Attention, not orientation, is the cardinal deficit.

Cognitive features

• Inattention is the central feature: distractibility, inability to sustain a conversation, failure on simple tests such as digit span or months of the year backward.^[14]
• Disorganized thinking: tangential or incoherent speech, illogical flow of ideas.^[14]
• Disorientation, particularly to time and place; memory impairment (short-term predominantly).^[14]
• Perceptual disturbances in 30-40%: illusions, misperceptions, visual hallucinations more common than auditory.^[14]

Behavioral and affective features

• Sleep-wake cycle disruption is nearly universal: daytime drowsiness, nocturnal agitation, sundowning.^[14]
• Emotional lability: rapid shifts among fear, anger, euphoria, tearfulness.^[14]
• Delusions when present are typically poorly systematized and persecutory.^[14]
• Motor signs in hyperactive delirium include restlessness, pulling at lines and tubes, attempts to leave the bed; in hypoactive delirium, motor slowing and apathy predominate.^[14]

Course

• Onset is acute, over hours to days; symptoms fluctuate markedly within a 24-hour period, often worsening at night.^[11]
• A lucid interval during morning rounds is common and contributes to under-recognition by daytime teams.^[1]

Delirium is frequently confused with dementia, depression, and primary psychosis. The wrong label delays workup of a reversible medical cause and exposes the patient to inappropriate medications.

Dementia

• Distinguished by gradual onset over months to years, preserved attention until late stages, and a stable level of consciousness.^[15]
• Delirium superimposed on dementia is the most common diagnostic confound; an acute change from the patient's known dementia baseline is delirium until proven otherwise.^[15]

Depression

• Hypoactive delirium is mistaken for depression in older adults; depression typically has insidious onset, intact attention, mood-congruent ideation, and a normal EEG.^[16]
• A reliable rule: if attention is genuinely impaired and the picture fluctuates, it is not primary depression.^[16]

Primary psychotic disorders

• Schizophrenia and related disorders rarely present de novo after age 50 and feature systematized delusions, predominantly auditory hallucinations, and intact orientation.^[17]
• Visual hallucinations, disorientation, and fluctuating consciousness should always shift the differential toward delirium or another medical cause.^[17]

Other psychiatric mimics

• Mania can produce agitation and disorganized speech but typically with euphoric or irritable mood, grandiosity, and preserved attention to preferred topics.^[17]
• Catatonia can present with mutism and stupor resembling hypoactive delirium; catatonia features (posturing, waxy flexibility, echolalia) and response to lorazepam challenge help distinguish.^[18]

Medical and neurologic mimics

• Nonconvulsive status epilepticus presents as fluctuating altered mental status without overt convulsions; EEG is mandatory when unexplained.^[19]
• Wernicke encephalopathy: triad of confusion, ophthalmoplegia, ataxia, classically in malnourished or alcohol-dependent patients; treat empirically with high-dose thiamine before glucose.^[20]
• Stroke (especially right parietal, thalamic, or bilateral frontal), CNS infection, posterior reversible encephalopathy syndrome, and limbic encephalitis can mimic or precipitate delirium.^[19]

Assessment has two parallel goals: confirm the syndrome of delirium using a validated tool, and find the medical cause. Both must happen within hours, not days.

History

• Establish the patient's cognitive and functional baseline through family or caregivers — collateral is essential.^[21]
• Define the time course of the change; ask specifically about fluctuation and overnight worsening.^[21]
• Review every medication including over-the-counter agents, sleep aids, and recent changes; quantify alcohol and benzodiazepine use.^[21]
• Screen for infection symptoms, pain, urinary retention, constipation, recent procedures, and falls.^[21]

Bedside cognitive examination

• Test attention directly: digit span (forward at least five), months of the year backward, days of the week backward, serial sevens.^[22]
• The Confusion Assessment Method (CAM) algorithm requires (1) acute onset and fluctuating course, (2) inattention, and either (3) disorganized thinking or (4) altered level of consciousness; sensitivity 94% and specificity 89% when administered by trained raters.^[23]
• The CAM-ICU is validated for nonverbal ventilated patients and uses pictorial attention tasks.^[24]
• The 4AT is a brief 2-minute screen suitable for emergency and ward use; sensitivity ~88%, specificity ~88%.^[25]

Physical and neurologic examination

• Full vital signs, oxygen saturation, capillary glucose at the bedside.^[21]
• Hydration status, evidence of infection (chest, urinary, skin, lines), abdominal exam for retention or impaction.^[21]
• Focused neurologic exam for focal signs, meningismus, asterixis, myoclonus, tremor, and pupillary findings suggesting toxidromes.^[21]

Laboratory workup

• First-line in every case: CBC, comprehensive metabolic panel including calcium and magnesium, urinalysis, capillary glucose, and oxygen saturation.^[26]
• Targeted: TSH, B12, folate, troponin, ammonia (if hepatic disease), arterial blood gas, urine and blood cultures, urine toxicology, blood alcohol level, lactate.^[26]
• Lumbar puncture when CNS infection or autoimmune encephalitis is plausible.^[26]

Imaging and EEG

• Non-contrast head CT for focal deficits, recent fall, head trauma, anticoagulation, or unexplained delirium after first-line workup.^[26]
• MRI when stroke, encephalitis, or PRES is suspected and CT is non-diagnostic.^[26]
• EEG when nonconvulsive status epilepticus is in the differential or to distinguish delirium (generalized slowing) from primary psychiatric illness in ambiguous cases.^[9]

What NOT to order

• Routine head CT in every delirious patient without focal signs or a specific indication is low-yield and exposes patients to radiation and transport risk.^[27]
• Routine "rule-out" lumbar punctures in afebrile patients without meningismus or immunosuppression.^[27]
• Antipsychotic levels, dopamine receptor imaging, and most autoimmune panels in the absence of a specific clinical hypothesis.^[27]

Treatment has a clear hierarchy: find and fix the cause, then protect the brain with multicomponent supportive care, and use pharmacology only for severe agitation that threatens safety or essential medical treatment. Most evidence for delirium-specific pharmacotherapy is low-certainty and shows no effect on duration, severity, or mortality.

Pharmacotherapy

• Antipsychotics do not prevent or shorten delirium and should not be used routinely.^[28]
• Reserve antipsychotics for severe agitation, distress, or behavior that threatens safety or essential treatment (e.g., pulling an endotracheal tube, removing a vascular access).^[29]
• When indicated, low-dose haloperidol is the most-studied agent: 0.5-1 mg PO or 0.5-2 mg IV/IM, repeated cautiously; ECG monitoring is appropriate given QTc risk.^[29]
• Atypical agents (risperidone 0.25-0.5 mg, olanzapine 2.5-5 mg, quetiapine 12.5-50 mg) are reasonable alternatives, particularly with Parkinson disease or Lewy body dementia where quetiapine is preferred.^[29]
• Benzodiazepines are first-line ONLY for delirium tremens or sedative-hypnotic withdrawal; they otherwise prolong delirium and worsen outcomes.^[30]
• Dexmedetomidine, an alpha-2 agonist, is preferred over benzodiazepine sedation in mechanically ventilated ICU patients and reduces delirium incidence and duration compared with midazolam or propofol in several trials.^[31]
• Cholinesterase inhibitors (donepezil, rivastigmine) have no role in acute delirium treatment; rivastigmine increased mortality in critically ill patients in a randomized trial.^[32]
• Melatonin and ramelteon have low-certainty evidence for prevention of incident delirium in older medical inpatients; the effect size is modest and not consistent across trials.^[33]

Psychotherapy

• Formal psychotherapy is not feasible during acute delirium; the equivalent intervention is multicomponent non-pharmacologic care.^[35]
• The Hospital Elder Life Program (HELP) reduces incident delirium by approximately 40% through six targeted protocols: orientation, therapeutic activities, early mobilization, vision and hearing aids, hydration, and sleep enhancement.^[35]
• Family presence at the bedside, familiar objects from home, and consistent staffing reduce agitation and improve orientation.^[35]
• After resolution, psychoeducation for the patient and family is important; many patients have distressing recall of delusions or hallucinations and benefit from validation and reassurance.^[36]

Neuromodulation

• ECT has no established role in primary delirium and is contraindicated when delirium is from raised intracranial pressure or acute stroke.^[37]
• ECT may be considered in delirious mania or in malignant catatonia masquerading as hypoactive delirium; this is expert-opinion territory and requires senior input.^[37]

Adjunctive

• Treat pain adequately; uncontrolled pain is a strong precipitant. Prefer scheduled non-opioid analgesia and the lowest effective opioid dose; avoid meperidine entirely (anticholinergic metabolite).^[38]
• Remove or substitute deliriogenic medications: anticholinergics (diphenhydramine, oxybutynin, tricyclics), benzodiazepines, sedative-hypnotics, opioids when possible, corticosteroids, and antiepileptics with cognitive effects.^[38]
• Address sensory deprivation: glasses on, hearing aids in, lights on during the day, quiet and dark at night.^[35]
• Maintain hydration, nutrition, and bowel and bladder function; remove indwelling urinary catheters as soon as possible.^[35]
• Mobilize early; physical and occupational therapy reduce duration in ICU populations.^[39]
• Sleep protection: minimize nighttime vital signs and blood draws, cluster nursing care, and use non-pharmacologic sleep promotion before considering medication.^[35]

Most harms in delirium care come from the medications used to suppress it, not from the syndrome itself. The evidence base for pharmacotherapy is heterogeneous, mostly low-certainty, and weighted toward short-term outcomes.

Common adverse effects of antipsychotics

• Sedation, orthostatic hypotension, and falls, particularly in frail older adults.^[34]
• Extrapyramidal symptoms with haloperidol and risperidone; akathisia can mimic worsening agitation and trigger dose escalation.^[34]
• Anticholinergic burden with olanzapine and low-potency agents, which can paradoxically worsen delirium.^[34]

Serious or rare adverse effects

• QTc prolongation and torsades de pointes, especially with IV haloperidol and in patients with electrolyte derangement or concurrent QT-prolonging drugs.^[34]
• Neuroleptic malignant syndrome is rare but life-threatening; clinical features overlap with delirium and can be missed.^[34]
• FDA boxed warning: increased all-cause mortality with antipsychotic use in elderly patients with dementia-related psychosis applies to all classes and should inform every prescription decision.^[34]

Benzodiazepine harms

• Prolonged delirium duration, paradoxical disinhibition, falls, respiratory depression, and accelerated cognitive decline in older adults.^[30]
• Withdrawal can itself precipitate delirium; taper rather than abruptly discontinue in chronic users.^[30]

Monitoring burden and discontinuation

• Antipsychotics started during hospitalization are frequently continued at discharge without indication, contributing to long-term harm.^[40]
• Stopping rules must accompany every order: target symptom, maximum duration, and explicit discharge plan.^[40]

Limitations of the evidence base

• Most pharmacologic trials are small, short, and use heterogeneous outcomes; few measure functional or long-term cognitive endpoints.^[28]
• ICU populations are over-represented; medical and surgical ward evidence is comparatively thin.^[28]
• Hypoactive delirium is under-studied; most trial recruitment captures hyperactive presentations.^[28]
• Patient and family-centered outcomes (distress, post-delirium PTSD, caregiver burden) are inconsistently reported.^[36]

Delirium epidemiology and management shift meaningfully across age, gestational status, comorbid burden, and culture. The clinical principles do not change; the calibration does.

Older adults

• Age is the dominant predisposing factor; baseline cognitive impairment, sensory loss, polypharmacy, and frailty compound risk.^[4]
• Drug clearance is reduced; antipsychotic and opioid dosing should be roughly halved from the adult starting dose and titrated cautiously.^[29]
• Anticholinergic burden is a leading reversible precipitant; review the medication list for diphenhydramine, oxybutynin, tricyclics, and first-generation antipsychotics.^[38]
• A drop in functional baseline after a delirium episode is the rule, not the exception; document pre-illness baseline early for discharge planning.^[6]

Pediatric delirium

• Pediatric delirium is common in PICU populations (roughly 20-25% of admissions) and is under-recognized outside specialized centers.^[1,3,41]
• Validated screens include the Cornell Assessment of Pediatric Delirium (CAPD) and the Preschool Confusion Assessment Method for the ICU (psCAM-ICU).^[42-43]
• Benzodiazepine exposure is an independent risk factor for pediatric ICU delirium; minimize where possible.^[30]

Pregnancy and perinatal

• New-onset delirium in pregnancy or postpartum demands urgent workup for eclampsia, infection (including chorioamnionitis and sepsis), thromboembolism, intracranial pathology, and substance withdrawal.^[1]
• Antipsychotic choice should weigh fetal exposure data; haloperidol has the most reproductive safety literature among first-generation agents.^[1]

Substance use and withdrawal

• Alcohol withdrawal delirium (delirium tremens) is the one delirium subtype where benzodiazepines are first-line, ideally with symptom-triggered dosing (e.g., CIWA-Ar-guided diazepam or lorazepam).^[30]
• Add thiamine 500 mg IV three times daily for at least two days before glucose in any malnourished or alcohol-using patient to prevent Wernicke encephalopathy.^[20]
• Stimulant, cannabinoid, and synthetic-cathinone intoxication can mimic hyperactive delirium; the syndrome resolves with the agent's pharmacokinetic clearance.^[3]

Comorbid dementia

• Roughly two-thirds of older inpatients with delirium have underlying dementia; this 'delirium superimposed on dementia' carries the worst short- and long-term prognosis.^[6]
• Distinguishing the two requires a clear pre-illness cognitive baseline from a knowledgeable informant; without it, the diagnosis is presumptive.^[15]
• After resolution of the acute episode, formal neurocognitive reassessment should be deferred at least 4-6 weeks to avoid mislabeling residual delirium as new dementia.^[6]

End-of-life and palliative care

• Terminal delirium occurs in the majority of patients in the last days of life; the goal shifts from reversal to symptom control and family support.^[44]
• Low-dose haloperidol or, for refractory agitation, midazolam-based palliative sedation is appropriate when comfort is the goal.^[29,39]
• Even in this setting, antipsychotics do not reliably shorten delirium duration; one RCT in palliative inpatients showed worse delirium symptom scores with haloperidol and risperidone versus placebo.^[28]

Cultural and language considerations

• Inattention testing relies on language- and education-fair tasks; use months-of-the-year backward or digit span rather than serial sevens in patients with limited education.^[22]
• Family members from collectivist cultures may interpret hypoactive delirium as appropriate withdrawal or grief; explicit education about the medical nature of the syndrome supports recognition and consent for treatment.^[45]

Delirium is not a transient nuisance. It independently predicts worse outcomes across multiple domains, even after adjustment for age, illness severity, and baseline cognition.

Short-term outcomes

• In-hospital mortality is roughly doubled in delirious patients compared with matched non-delirious controls (pooled odds ratio approximately 1.95).^[5]
• Length of stay is extended by an average of 5-10 days, with corresponding cost increases.^[5]
• Falls, pressure injury, aspiration, and unplanned device removal are all elevated during the acute episode.^[14]

Duration and resolution

• Most episodes resolve within days to weeks once the precipitant is treated, but persistent delirium at hospital discharge occurs in roughly one-third of older inpatients and is associated with worse long-term outcomes.^[6]
• Hypoactive and mixed subtypes resolve more slowly than purely hyperactive presentations.^[14]

Long-term cognitive outcomes

• Delirium is associated with accelerated long-term cognitive decline; in ICU survivor cohorts, delirium duration correlated with global cognitive and executive function scores at 3 and 12 months.^[6]
• A first delirium episode roughly doubles the risk of incident dementia in older adults followed over several years.^[6]
• It remains debated whether delirium causes neuronal injury or unmasks pre-clinical neurodegeneration; the leading view is that both occur.^[6]

Functional and disposition outcomes

• New nursing-home placement after a delirium episode is increased roughly two- to three-fold compared with non-delirious controls.^[5]
• Activities of daily living typically decline below baseline at discharge and may not fully recover over the following 6-12 months.^[6]

Psychological sequelae

• Patients commonly retain fragmentary memories of delusional or threatening experiences from the delirious period; post-ICU PTSD symptoms occur in a meaningful minority of survivors.^[36]
• Family witnesses likewise report distress and PTSD-spectrum symptoms; structured debriefing after the episode reduces this burden in small studies.^[36]

Delirium frequently presents in the emergency department and on rapid-response calls. Two questions dominate the initial minutes: what is killing this patient, and how do we keep the team and patient safe long enough to find out.

Life-threatening precipitants that cannot be missed

• Hypoglycemia, hypoxia, and hypotension are bedside-treatable causes that should be excluded before any psychiatric formulation.^[21]
• Sepsis, including occult urinary tract infection in older adults, frequently presents as delirium without prominent fever.^[3]
• Intracranial pathology (stroke, subdural hematoma, encephalitis, non-convulsive status epilepticus) requires neuroimaging and, in selected cases, EEG; focal signs, fever with neck stiffness, or fluctuating arousal without identified medical cause should trigger this workup.^[19]
• Wernicke encephalopathy in any malnourished or alcohol-using patient — thiamine before glucose.^[20]
• Anticholinergic, serotonergic, sympathomimetic, and opioid toxidromes; recognize the constellation before assuming primary delirium.^[3]

Acute agitation management

• Verbal de-escalation, environmental modification (reduce stimulation, restore orientation, involve family), and treating pain or urinary retention should precede pharmacotherapy whenever feasible.^[14]
• Pharmacologic options for severe agitation threatening safety or essential treatment include haloperidol (e.g., 0.5-2 mg PO/IM in older adults, up to 5 mg in younger adults), olanzapine, or risperidone; use the lowest effective dose and reassess frequently.^[29]
• In ICU patients on mechanical ventilation, dexmedetomidine is preferred over benzodiazepine-based sedation when delirium is present or anticipated.^[31]

Physical restraint

• Restraints are themselves a precipitant and a risk factor for ongoing delirium; use only when less restrictive measures have failed and document indication, time-limited duration, and a plan for removal.^[14]
• A sitter, family member, or one-to-one observation is preferred when feasible.^[35]

Hospitalization decisions

• New-onset delirium without a clearly identified and rapidly reversible outpatient cause is an indication for inpatient evaluation.^[21]
• Discharge planning must address the elevated risk of recurrence, falls, and cognitive decline; primary care follow-up within 1-2 weeks and a medication reconciliation are minimum standards.^[40]

Despite decades of research, the delirium evidence base has more controversies than clinicians realize. The clinical posture should be humility about pharmacology and confidence about prevention.

Antipsychotics for treatment or prevention

• Pooled trial evidence does not support routine antipsychotic use to prevent or shorten delirium episodes; the most rigorous placebo-controlled trials in both medical and palliative populations have been null or unfavorable.^[28]
• Several professional societies (SCCM, American Geriatrics Society) recommend against routine prophylactic antipsychotic use, while expert opinion continues to support short courses for severe agitation.^[28]
• Whether subgroups (severe hyperactive presentations, distress-driven symptoms) benefit remains an open question that current trial designs cannot resolve.^[28]

Hypoactive delirium treatment

• Hypoactive delirium has the worst prognosis but the weakest evidence base; antipsychotics have no established benefit and may worsen sedation.^[28]
• Whether early mobilization and stimulation alone are sufficient, or whether targeted agents (e.g., methylphenidate in selected patients) have a role, is unresolved.^[46]

Dexmedetomidine beyond the ICU

• Trials in non-ICU postoperative populations have produced mixed results for prevention; broad adoption outside critical care is not currently supported.^[31]

Melatonin and ramelteon

• Small trials suggest possible benefit in prevention for selected populations, but heterogeneity in dosing, timing, and outcomes prevents a confident recommendation.^[33]

Delirium and dementia as a continuum

• The relationship between delirium and incident dementia remains debated: causal neuronal injury versus unmasking of preclinical neurodegeneration versus shared vulnerability.^[6]
• This distinction matters for prevention strategy and for counseling families about long-term cognitive risk after an episode.^[6]

Subsyndromal delirium

• DSM-5-TR does not define subsyndromal delirium, yet patients with subthreshold inattention and arousal disturbance have outcomes intermediate between delirium and non-delirium.^[13]
• Whether to label, screen, or treat this state is unresolved and varies across services.^[13]

Restraint and family presence

• Restraint use varies widely across institutions; mounting evidence frames physical restraint as a delirium precipitant rather than a control measure, but practice change is slow.^[14]
• Open ICU visitation and family-led reorientation are promoted by major bundles, though robust outcome data are limited.^[39]

• Delirium is defined by acute, fluctuating disturbance of attention and awareness with disorganized thinking and a causal medical or substance precipitant.^[11]
• Inattention is the cardinal feature; without inattention, the diagnosis is not delirium.^[14]
• Hypoactive delirium is the most common subtype in older inpatients and is missed in roughly half of cases.^[1]
• The Confusion Assessment Method (CAM) is the most widely validated bedside screen; the 4AT is a rapid screen suitable for the emergency department.^[23,25]
• The CAM-ICU and Intensive Care Delirium Screening Checklist are designed for nonverbal mechanically ventilated patients.^[24]
• Benzodiazepines are first-line only for alcohol or sedative-hypnotic withdrawal delirium; in all other delirium they prolong and worsen the episode.^[30]
• Thiamine should be given before glucose in any malnourished or alcohol-using patient to prevent Wernicke encephalopathy.^[20]
• Multicomponent non-pharmacologic interventions (Hospital Elder Life Program, ABCDEF bundle) are the only strategies with consistent evidence for reducing delirium incidence and duration.^[35,39]
• Antipsychotics should be reserved for severe agitation threatening safety or essential treatment, used at the lowest effective dose for the shortest duration; they do not shorten delirium episodes.^[28]
• Haloperidol carries a QT-prolongation risk; an EKG and electrolyte correction are indicated before scheduled intravenous dosing.^[29]
• Dexmedetomidine is preferred over benzodiazepine-based sedation in ICU patients at risk for or with delirium.^[31]
• Delirium roughly doubles in-hospital mortality and is associated with accelerated long-term cognitive decline and incident dementia.^[5-6]
• Anticholinergic burden, opioids, benzodiazepines, corticosteroids, and antibiotics (especially cefepime and fluoroquinolones) are common drug precipitants.^[38]
• Non-convulsive status epilepticus should be considered in fluctuating altered mental status without an identified cause; EEG is required to make the diagnosis.^[19]
• Delirium superimposed on dementia has worse short- and long-term outcomes than either alone and requires a knowledgeable-informant baseline to recognize.^[6,15]

No external funding. No conflicts of interest declared. Peer-review status: pending.