Delirium Causes

The highest prevalence of delirium (often 50% to 75% of patients) is generally seen in critically ill patients in the intensive care unit or ICU (which used to be referred to by the misnomer ICU Psychosis, a term largely abandoned now for the more widely accepted and scientifically supported term delirium).

Since the advent of validated and easy to implement delirium instruments for ICU patients such as the Confusion Assessment Method for the ICU (CAM-ICU). For example, fever, pain, poisons (including toxic drug reactions), brain injury, surgery, traumatic shock, lack of food or water or sleep, and even withdrawal symptoms of certain drug and alcohol dependent states, are all known to cause delirium.

In addition, there is an interaction between acute and chronic symptoms of brain dysfunction; delirious states are more easily produced in people already suffering with underlying chronic brain dysfunction.

A very common cause of delirium in elderly people is a urinary tract infection, which is easily treatable with antibiotics, reversing the delirium.

Too many to list by specific pathology, major categories of the cause of delirium include:

Critical illness

The most common behavioral manifestation of acute brain dysfunction is delirium, which occurs in up to 60% to 80% of mechanically ventilated medical and surgical ICU patients and 50% to 70% of non-ventilated medical ICU patients.

During the ICU stay, acute delirium is associated with complications of mechanical ventilation including nosocomial pneumonia, self-extubation, and reintubation.

The elderly may be at particular risk for this spectrum of delirium and dementia. A firm understanding of the pathophysiologic mechanisms of delirium remains elusive despite improved diagnosis and potential treatments.

Substance withdrawal

Drug withdrawal is a common cause of delirium. The most notable are alcohol withdrawal and benzodiazepine withdrawal but other drug withdrawals both from licit and illicit drugs can sometimes cause delirium.

Gross structural brain disorders

Head trauma (i.e., concussion, traumatic bleeding, penetrating injury, etc.)
Gross structural damage from brain disease (stroke, spontaneous bleeding, tumor, etc.)

Neurological disorders

Various neurological disorders
Lack of sleep

Circulatory

Intracranial Hypertension

Lack of essential metabolic fuels, nutrients, etc.

Hypoxia,
Hypoglycemia
Electrolyte imbalance (dehydration, water intoxication)

Toxication

Intoxication various drugs, alcohol, anesthetics
Sudden withdrawal of chronic drug use ("de-tox") in a person with certain types of drug addiction (e.g. alcohol, see delirium tremens, and many other sedating drugs)
Poisons (including carbon monoxide and metabolic blockade)
Medications including psychotropic medications

Mental illness per se is not a cause, as a matter of definition

Some mental illnesses, such as mania, or some types of acute psychosis, may cause a rapidly fluctuating impairment of cognitive function and ability to focus. However, they are not technically causes of delirium, since any fluctuating cognitive symptoms that occur as a result of these mental disorders are considered ''by definition'' to be due to the mental disorder itself, and to be a part of it. Thus, ''physical'' disorders can be said to produce delirium as a mental side-effect or symptom; however primary ''mental'' disorders which produce the symptom cannot be put into this category, once identified. However, such symptoms may be impossible to distinguish clinically from delirium resulting from physical disorders, if a diagnosis of an underlying mental disorder has yet to be made.