• An abrupt, persistent, or significant change in usual performance of ADLs
• Disturbances occurring after a change in medication regimen (e.g., a change in the dose of an existing medication or addition of a new medication [in any category] with CNS effects or side effects; recent abrupt discontinuation of a medication that should be tapered gradually)
• Progressive or abrupt onset of agitation, altered attention span, or restlessness that persists for a day or more, or a change in usual level of consciousness (e.g. from alert to drowsy, from drowsy to stuporous) with or without other specific signs or symptoms such as fever or neurological signs (e.g., facial droop, slurred speech, unsteady gait, focal weakness)
• Rapid or persistent escalation of symptoms in a patient with new or pre-existing major depression or mental illness such as schizophrenia or the manic phase of bipolar disorder

Other changes in level of consciousness

• Fluctuating level of consciousness (LOC) or abrupt or progressive change in usual LOC (e.g., from alert to drowsy, from drowsy to stuporous) or change in responsiveness that persists for more than an hour, with or without other specific signs or symptoms
• Persistent change in LOC that occurs subsequent to a change in medication regimen or after a fall with or without evident head trauma

Intellectual function

• Abrupt onset or progression of delusions, illusions, hallucinations, or paranoia
• Abrupt or rapid onset of confusion or persistent change from the usual level of understanding and comprehension, with or without physical or functional changes
• New onset of disorientation to person, place, or time, or worsening of existing disorientation
• Persistent change from the patient’s usual level of thinking (whether normal or disordered)

General
New onset or worsening of existing distressed behavior, mood, or thinking, accompanied by one or more of the following:

• Hypovolemia or other fluid or electrolyte imbalance (e.g., low or high sodium)
• Confirmed or suspected infection (with or without evidence of sepsis)
• Fever
• Use of medications with known CNS effects or side effects (especially, anticholinergic medications)
• Hypoxia
• Hypoglycemia or marked hyperglycemia
• Abnormal thyroid function
• Abnormal liver function
• Uncompensated acid-base disturbance
• Cardiac arrhythmia
• Elevated blood ammonia
• Abnormally high serum cortisol level
• Hypercalcemia
• Inadequate levels of folate or Vitamin B12

ADLs     Activities of daily living
CNS        Central nervous system
LOC        Level of consciousness

• Disturbance of consciousness (i.e., reduced clarity of awareness of the environment) and reduced ability to focus, sustain, or shift attention. The disturbance of consciousness or arousal may be manifested by a reduced clarity or awareness of the environment that does not reach the level of stupor or coma.
• A change in cognition (e.g., disorientation, language disturbance, memory deficit,) or the development of a perceptual disturbance that is not better accounted for by a pre-existing, established, or evolving dementia
• The disturbance develops over a short period of time (usually hours to days) and tends to fluctuate during the course of the day.
• Delirium frequently represents a sudden and significant decline from a previous level of functioning that cannot be better accounted for by a pre-existing or evolving dementia.
• The ability to focus, sustain, or shift attention is frequently impaired and may result in the patient’s being easily distracted.
• There is usually evidence from the history, physical examination, or laboratory tests that the delirium is a direct physiological consequence of a general medical condition, substance intoxication or withdrawal, toxin exposure, use of a medication, or a combination of these factors.
• Delirium-related disorders have a common symptom presentation of a disturbance in consciousness and cognition but may have different etiologies:

• Delirium due to a general medical condition
• Substance-induced delirium
• Delirium due to multiple etiologies
• Delirium not otherwise specified

• Markedly abnormal vital signs (systolic blood pressure <90, heart rate <50 or >120, respirations >30, temperature <96 or >101)
• New-onset respiratory distress, with increasing hypoxia and dyspnea
• Signs of a serious underlying condition possibly causing delirium (e.g., symptoms of stroke)

• Escalating physically aggressive behavior or threats of violence
• Patient presents an intermittent or persistent danger to self or others