Underlying disorder

Head injury

Shock

Toxin ingestion

Pain and discomfort (eg, caused by injuries, surgical procedures, endotracheal intubation, IVs, blood drawing, or nasogastric tube)

Complications

Hypoxia (see Oxygen Desaturation)

Hypotension

Sepsis

Organ failure (eg, hepatic encephalopathy)

Pulmonary embolism

Drugs

Sedatives and other drugs active in the central nervous system, particularly opioids, benzodiazepines, H2 blockers, and antihistamines

Withdrawal from alcohol, drugs, or both

Intensive care unit (ICU) environment*

Sleep deprivation (eg, due to noise, bright lights, or round-the-clock medical interventions)

Fear of death

Anxiety about unpleasant medical procedures