Delirium: Etiologies By Organ System

Your Path

  • Delirium: Etiologies by Organ System


  • Pulmonary process: Hypoxemia, hypercarbia, pneumonia, pulmonary embolism
  • Cardiac process: Heart failure, heart attack, hypotension, hypertensive encephalopathy
  • GI process: Bleeding, hepatic encephalopathy
  • Renal process: Uremia, hypovolemia
  • Heme-Oncology: Malignancy, including para-neoplastic syndromes, anemia
  • Infectious process: Infection anywhere; the more frail the patient, the lower magnitude the infxn necessary to cause delirium
  • Endocrine/Metabolic Rrocess: Hyper/hyponatremia, Hypercalcemia, Hyper/hypoglycemia, Hypo/hyperthyroidism; Vitamin B1 deficiency (Wernickes Encephalopathy)
  • CNS process: stroke, infection (encephalitis, meningitis, CNS abscess), Wernickes, non-convulsive status, trauma, autoimmune/inflammatory (ADEM, autoimmune encephalitis), other
  • Multi-system organ dysfunction can contribute
  • Substances of abuse: Cocaine, crystal meth, amphetamines, PCP, ETOH, canabis, other
  • Toxic exposures: Carbon monoxide, organophosphates, others
  • Meds: ADHD meds, dopaminergics, SSRIs, steroids, benzos, narcotics, dilantin, anti-psychotics, other - try to link new med to onset of sx
  • Withdrawal from alcohol, benzos, narcotics, other combinations of agents
  • Pain: Severe pain, in particular if coupled w/any of above
  • Unfavorable environments: Hospitalization, disruption of normal sleep wake cycle, ICU stay, procedures, restraints, foley catheter

Risk Factors

  • Age > 65, male
  • Impaired hearing or vision
  • Prior hx delirium, dementia, hospitalization, surgery or serious illness
  • Multiple medications, in particular if newly started
  • Baseline dementia
  • Impaired ability to clear toxins/meds (e.g. AKI or CKD, liver dysfunction)
  • Older/more physiologically frail patients require less of a "nudge" to develop delirium as compared w/those who are younger and/or healthier


  • Acute change from prior behavior, including→ disorganized thinking, impaired short term memory
  • Inattention, disorientation, confusion, delusions, hallucinations, altered sleep patterns
  • Hypoactive (75%) or hyperactive (25%)
  • Symptoms fluctuate, with spectrum from somnolent to very agitated
  • Typically reversible
  • Delirium is always secondary to something

Physical Exam Findings

  • Range in level of alertness from agitation to somnolence
  • May have abnormal vital signs (e.g. tachycardia, bradycardia, hypertension, hypertension, febrile) - based sometimes on underlying process (e.g. infection)
  • Focus of exam should be search for focal findings that might identify cause (e.g. findings of pneumonia, heart failure, cellulitis/other infection, etc)
  • Due to age and co-morbidities, PE findings for underlying process may be subtle/atypical