Delirium

Epidemiology

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Etiology

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• A transient syndrome of acute brain dysfunction, not a specific disease.
• Results from a wide range of underlying medical conditions, substance intoxication/withdrawal, or medications.
• Key Pathophysiology: Believed to involve widespread disturbances in brain metabolism, neurotransmitter function (especially ↓ acetylcholine, ↑ dopamine), and inflammation.

Risk factors

• Advanced age
• Neurologic disorder (e.g. dementia, stroke)
• Sensory impairment (e.g. hearing loss)
• Sleep disruption
• Immobilization

Precipitating causes

• Drugs (eg, narcotics, sedatives, antihistamines, muscle relaxers, polypharmacy)
• Infections (eg, pneumonia, urinary tract infection, meningitis)
• Electrolyte disturbances (eg, hyponatremia, hypercalcemia)
• Metabolic derangements (eg, volume depletion, vitamin B12 deficiency, hyperglycemia)
• Systemic illnesses (eg, congestive heart failure, hepatic failure, malignancy)
• CNS conditions (eg, seizure, stroke, head injury, subdural hematoma)

Pathophysiology

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Clinical features

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• Core Features:
  • Acute onset (hours to days).
  • Fluctuating course (often worse at night / sundowning). c
  • Inattention (hallmark: cannot sustain focus; fails serial 7s or spelling “WORLD” backward).
  • Altered level of consciousness (LOC) (ranges from hyperalert to unarousable).
  • Disorganized thinking and perceptual disturbances (visual hallucinations common).
• Clinical Subtypes:
  • Hyperactive: Agitation, combative, restlessness, hallucinations.
  • Hypoactive: Somnolence, lethargy, psychomotor slowing (often missed or misdiagnosed as depression; higher mortality).
  • Mixed: Alternates between hyperactive and hypoactive states.

Diagnostics

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• Clinical (CAM Criteria):
  1. Acute onset & fluctuating course AND
  2. Inattention AND
  3. Either Disorganized thinking OR Altered consciousness.
• Initial Tests: Fingerstick glucose, vitals/SpO₂, medication review.
• Key Labs: CBC, CMP, UA/Urine culture (rule out occult UTI), CXR, ECG.
• Targeted Imaging/Procedures (not routine):
  • CT Head: Only if new focal neuro deficits, fall/head trauma, or anticoagulated.
  • LP: If fever + meningismus.
  • EEG: If non-convulsive status epilepticus suspected.
• Differential diagnostics
  • Mania: cognition is intact; not disoriented; treated with lithium

Treatment

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1. First-Line (Treat Cause & Deprescribe):
   • Treat precipitant (Abx for UTI/PNA, correct electrolytes).
   • Stop offending meds (anticholinergics, sedatives).
2. Non-Pharmacological (Mainstay):
   • Frequent reorientation, sleep hygiene, early mobilization.
   • Sensory aids (glasses, hearing aids).
   • Remove tethers (Foley, IV lines); avoid physical restraints (worsens agitation).
3. Pharmacological Management (Reserved ONLY for Severe Agitation / Safety Risk):
   • First-line Med: Low-dose typical or atypical antipsychotics (e.g., Haloperidol 0.5–1 mg PO/IV/IM, Quetiapine, Risperidone). c
     • Monitoring: Check baseline ECG for QTc prolongation (risk of Torsades de Pointes). Avoid in Parkinson disease/Lewy body dementia (use Quetiapine if required).
   • Contraindication: Avoid Benzodiazepines (cause paradoxical agitation and worsen/prolong delirium). c
     • Mechanism: In elderly pts and pts with damaged frontosubcortical networks (e.g., baseline dementia), sedatives suppress top-down inhibitory cortical control.
     • Exceptions: Delirium caused by alcohol or BZD withdrawal, or Neuroleptic Malignant Syndrome (NMS).