Delirium arises through the interaction of a number of predisposing and precipitating factors. Individuals with multiple and/or significant predisposing factors are highly at risk for suffering an episode of delirium with a single and/or mild precipitating factor. Conversely, delirium may only result in healthy individuals if they suffer serious or multiple precipitating factors. It is important to note that the factors affecting those of an individual can change over time, thus an individual’s risk of delirium is dynamic. Predisposing factors The most important predisposing factors are: *65 or more years of age *Male sex *Cognitive impairment/dementia *Physical comorbidity (biventricular failure, cancer, cerebrovascular disease) *Psychiatric comorbidity (e.g., depression) *Sensory impairment (vision, hearing) *Functional dependence (e.g., requiring assistance for self-care or mobility) *Dehydration/malnutrition *Drugs and drug-dependence *Alcohol dependence Precipitating factors alcohol withdrawal, also known as delirium tremens Any acute factors that affect neurotransmitter, neuroendocrine, or neuroinflammatory pathways can precipitate an episode of delirium in a vulnerable brain. Clinical environments can also precipitate delirium. Some of the most common precipitating factors are listed below: *Prolonged sleep deprivation *Environmental, physical/psychological stress *Inadequately controlled pain *Admission to an intensive care unit *Immobilization, use of physical restraints *Urinary retention, use of bladder catheter, *Emotional stress *Severe constipation/fecal impaction *Medications *Sedatives (benzodiazepines, opioids), anticholinergics, dopaminergics, corticosteroids, polypharmacy *General anesthetic *Substance intoxication or withdrawal *Primary neurologic diseases *Severe drop in blood pressure, relative to the patient’s normal blood pressure (orthostatic hypotension) resulting in inadequate blood flow to the brain (cerebral hypoperfusion) *Stroke/Transient ischemic attack(TIA) *Intracranial bleeding *Meningitis, encephalitis *Concurrent illness *Infections – especially respiratory (e.g. pneumonia, COVID-19) and urinary tract infections *Iatrogenic complications *Hypoxia, hypercapnea, anemia *Poor nutritional status, dehydration, electrolyte imbalances, hypoglycemia *Shock, heart attacks, heart failure *Metabolic derangements (e.g. SIADH, Addison’s disease, hyperthyroidism, ) *Chronic/terminal illness (e.g. cancer) *Post-traumatic event (e.g. fall, fracture) * Mercury poisoning (e.g. Erethism) *Surgery *Cardiac, orthopedic, prolonged cardiopulmonary bypass, thoracic surgeries
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