Delirium

Background

• Acute disturbance of consciousness with fluctuating inattention and cognitive dysfunction
• Caused by an underlying medical condition — NOT a primary psychiatric disorder
• Extremely common: affects 10-30% of hospitalized elderly patients
• Associated with increased mortality, prolonged hospitalization, and long-term cognitive decline
• Key distinction from dementia: Delirium is acute (hours-days), fluctuating, with inattention as primary deficit; dementia is chronic (months-years) with memory as primary deficit

Clinical Features

• Inattention — hallmark feature (cannot maintain or shift attention appropriately)
• Fluctuating course throughout the day
• Develops over hours to days (acute onset)
• Subtypes:
  • Hyperactive: agitation, restlessness, hallucinations, combativeness (easier to diagnose)
  • Hypoactive: lethargy, decreased responsiveness, withdrawn (frequently missed — more common and more dangerous)
  • Mixed: alternating between hyperactive and hypoactive states

Common Causes (mnemonic: DELIRIUM)

• Drugs (anticholinergics, opioids, benzodiazepines, steroids, polypharmacy)
• Electrolyte abnormalities, Endocrine (thyroid, adrenal, glucose)
• Lack of drugs (withdrawal from alcohol, benzodiazepines, opioids)
• Infection (UTI, pneumonia, meningitis, sepsis)
• Reduced sensory input (vision/hearing impairment, ICU environment)
• Intracranial pathology (stroke, hemorrhage, mass, seizure)
• Urinary retention, constipation (especially in elderly)
• Myocardial/pulmonary (MI, PE, hypoxia, CHF)

Confusion Assessment Method (CAM)

• Must have both features 1 AND 2 plus either 3 OR 4:
  1. Acute onset and/or fluctuating course
  2. Inattention
  3. Disorganized thinking
  4. Altered level of consciousness

Differential Diagnosis

Altered mental status

Diffuse brain dysfunction

• Hypoxic encephalopathy
• Acute toxic-metabolic encephalopathy (Delirium)
  • Hypoglycemia
  • Hyperosmolar state (e.g., hyperglycemia)
  • Electrolyte Abnormalities (hypernatremia or hyponatremia, hypercalcemia)
  • Organ system failure
  • Hepatic Encephalopathy
  • Uremia/Renal Failure
  • Endocrine (Addison's disease, Cushing syndrome, hypothyroidism, myxedema coma, thyroid storm)
  • Hypoxia
  • CO2 narcosis
• Hypertensive Encephalopathy
• Toxins
• TTP / Thrombotic thrombocytopenic purpura
• Alcohol withdrawal
• Drug reactions (NMS, Serotonin Syndrome)
• Environmental causes
  • Hypothermia
  • Hyperthermia
• Deficiency state
  • Wernicke encephalopathy
  • Subacute Combined Degeneration of Spinal Cord (B12 deficiency)
  • Vitamin D Deficiency
  • Zinc Deficiency
• Sepsis
• Osmotic demyelination syndrome (central pontine myelinolysis)
• Limbic encephalitis

Primary CNS disease or trauma

• Direct CNS trauma
  • Diffuse axonal injury
  • Subdural/epidural hematoma
• Vascular disease
  • Intraparenchymal hemorrhage
• SAH
• Stroke
  • Hemispheric, brainstem
• CNS infections
  • Encephalitis
  • Anti-NMDA receptor encephalitis
  • Meningitis
• Neoplasms
  • Paraneoplastic Limbic encephalitis
  • Malignant Meningitis
  • Pancreatic Insulinoma
• Seizures
  • Nonconvulsive status epilepticus
  • Postictal state
• Dementia
  • Alzheimer's
  • Lewy Body Dementia
  • Frontotemporal Dementia

Psychiatric

• Acute psychosis
• Catatonia
• Excited delirium
• Malingering
• Steroid induced psychosis

General Psychiatric

• Organic causes
  • Delirium
  • Dementia
  • Overdose
• Psychiatric causes
  • Depression
  • Anxiety
  • Conversion disorder
  • Bipolar disorder
  • Acute psychosis
  • Panic attack
  • Schizophrenia

Evaluation

• Goal: identify and treat the underlying cause

AMS Workup

Common Orders

• Point of care glucose
• CBC
• Chemistry
• LFTs
• UA
• CXR
• Utox
• ECG
• Head CT
• CAM score

Consider Based on Clinical Situation

• Blood and urine cultures
• Ammonia level
• Tylenol/Aspirin level
• LP
• Serum Osm
• Coags
• Cortisol
• ABG/VBG
• CO level
• Minimum: glucose, BMP, CBC, urinalysis, ECG, CXR
• Consider: LFTs, ammonia, TSH, blood cultures, lactate, urine toxicology screen
• CT head if: focal neuro findings, fall/head trauma, anticoagulation, no clear cause identified
• LP if meningitis/encephalitis suspected

Management

• Treat the underlying cause — this is the definitive management
• Non-pharmacologic measures first: reorientation, quiet environment, sleep-wake cycle preservation, mobilization, adequate hydration/nutrition, correct sensory deficits (glasses, hearing aids)
• Pharmacologic (for severe hyperactive delirium with safety concerns):
  • Haloperidol 0.5-2 mg IV/IM (start low in elderly)
  • Olanzapine 2.5-5 mg IM
  • Avoid benzodiazepines (worsen delirium — exception: alcohol/benzo withdrawal)
• Review and discontinue deliriogenic medications when possible

Disposition

• Admit for workup and treatment of underlying cause
• ICU if hemodynamically unstable, severe agitation, or respiratory compromise

See Also

• Altered mental status
• Agitated delirium
• Dementia
• Acute psychosis
• Sundowning