Description

• A neurologic 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: Nervous
• Synonym(s): Acute confusional state; Altered mental status; Organic brain syndrome; Acute mental status change

Epidemiology

• Predominant age: Older persons
• Predominant sex: Male = Female

Incidence
>50% in high-risk older patients

• 10% in older emergency room patients
• 10–40% in hospitalized older patients
• 25% in older post–acute care patients
• Highest rates (>50%) in intensive care unit (ICU), post–hip fracture repair, post–cardiothoracic surgery

Risk Factors

• Predisposing risk factors:
  • Advanced age
  • Prior cognitive impairment
  • Functional impairment
  • High BUN:Creatinine ratio
  • Dehydration
  • Malnutrition
  • Hearing or vision impairment
  • Frailty
• Precipitating risk factors:
  • Severe illness in any organ system(s)
  • Need for a urinary catheter
  • >3 medications
  • Specific medications, especially long-acting sedative hypnotics (e.g., diazepam and flurazepam), narcotics (especially meperidine), and anticholinergics (especially diphenhydramine)
  • Pain
  • Any adverse iatrogenic event

General Prevention

Follow treatment approach.

Pathophysiology

• Believed to result from a decline in physiologic reserves with aging, resulting in a vulnerability to new stressors.
• Neuropathophysiology is not clearly defined; cholinergic deficiency is a leading hypothesis.
• Multicomponent approach addressing contributing factors can reduce incidence and complications.

Etiology

• Usually multifactorial
• Often interaction between predisposing and precipitating risk factors
• With more predisposing factors (i.e., frail patients), fewer precipitating factors are needed to produce delirium.
• If few predisposing factors (e.g., very robust patients), more precipitating factors are needed to manifest delirium.

Commonly Associated Conditions

Multiple, but most common are:

• New medicine or medicine changes
• Infections (especially lung and urine, but meningitis needs consideration as well)
• Toxic-metabolic (especially low sodium, elevated calcium, renal failure, and hepatic failure)
• Heart attack
• Stroke
• Alcohol or drug withdrawal
• Pre-existing cognitive impairment increases risk.