Description

• A temporary neurocognitive complication of illness and/or medication(s), especially common in older patients, manifested by new confusion and impaired attention
• A medical emergency requiring immediate evaluation to decrease morbidity and mortality
• System(s) affected: neurologic
• Synonym(s): acute confusional state, altered mental status, organic brain syndrome, acute mental status change, encephalopathy

Epidemiology

• Predominant age: older persons
• Predominant sex: male = female

• >50% in older intensive care unit patients
• 11–51% in postoperative patients
• 10–40% in hospitalized older patients
• 20–22% in nursing home/post–acute-care patients

• 1–2% in outpatients
• 8–17% in older ED patients
• 14% in older postacute care patients
• 18–35% in hospitalized general medicine patients

Etiology and Pathophysiology

• Multifactorial: believed to result from a decline in physiologic reserves with aging, resulting in a vulnerability to new stressors
• Disturbance in global cortical functioning. Neuropathophysiology is not clearly defined; cholinergic deficiency, dopamine excess, and neuroinflammation are leading hypotheses.
• Often interaction between predisposing and precipitating risk factors
• With more predisposing factors (i.e., frail patients), fewer precipitating factors needed to cause delirium
• If few predisposing factors (e.g., very robust patients), more precipitating factors needed to cause delirium
• Multicomponent approach addressing contributing factors can reduce incidence and complications.

Risk Factors

• Predisposing risk factors
  • Advanced age: >70 years
  • Preexisting cognitive impairment
  • Functional impairment
  • Dehydration; high blood urea nitrogen:creatinine ratio
  • History of alcohol abuse
  • Malnutrition
  • Hearing or vision impairment
  • Multiple comorbidities
• Precipitating risk factors
  • Severe illness in any organ system(s)
  • Medical devices (urinary catheter, restraints)
  • Polypharmacy (≥5 medications)
  • Specific medications, especially benzodiazepines, opioids, and anticholinergics diphenhydramine, high-dose neuroleptics
  • Pain
  • Any iatrogenic event
  • Surgery
  • Sleep deprivation

General Prevention

Follow treatment approach.

Commonly Associated Conditions

Multiple but most common are the following:

• New medicine or medicine changes
• Infections (especially lung, urine, and blood stream, but consider meningitis as well)
• Toxic metabolic (especially low sodium, elevated calcium, renal failure, and hepatic failure)
• Heart attack or stroke
• Alcohol or drug withdrawal
• Preexisting cognitive impairment increases risk.