Delirium, acute confusional state, acute brain syndrome, acute cerebral insufficiency, or toxic-metabolic encephalopathy, is a disturbance of consciousness and cognition that develops over a short period of time, usually hours to days, fluctuates throughout the course of a day, and can be caused by a host of medical conditions, medications, or substances of abuse.
Delirium itself is NOT a disease, but rather a clinical syndrome (a set of symptoms), which result from an underlying disease or intoxication or withdrawal from an ingested substance.
Prevalence of Delirium
The overall prevalence of delirium in the community is just 1-2%, but approximately 15 – 75% of elderly people experience a delirium prior to or during a hospitalization (higher when more specialized populations are considered and in postoperative, intensive-care, subacute and palliative care settings). For example, in the general population the highest prevalence of delirium (often 50% to 75% of people) is generally seen in critically ill patients in the intensive care unit or ICU.
Age Is a Very Strong Predictor of Risk for Delirium
Age is also a very strong predictor of risk for delirium, and at least 20% of hospitalized patients over 65 years of age experience complications during hospitalization because of delirium each year. Also postoperative delirium occurs in 15-53% of surgical patients over the age of 65 years, and elderly patients admitted to an intensive care unit (ICU) experience delirium at a rate of 70-87%.
Dementia Is One of the Most Prominent Risk Factors for Delirium
Having dementia is one of the most prominent risk factors for delirium, with two-thirds of all cases of delirium occurring in patients with dementia. It appears that delirium and dementia are both associated with decreased cerebral blood flow or metabolism, inflammation, and cholinergic neurotransmitter deficiency.
The Major Causes of Delirium
The major causes are diseases of the central nervous system, major internal organs, fluid and electrolyte imbalances, and either intoxication or withdrawal from medications or substances of abuse.
Mechanisms of Delirium
Evidence suggests that hypoxemia, metabolic derangements, drug toxicity, inflammation and acute stress responses can all contribute markedly to disruption of neurotransmission leading to delirium. Neurotransmitters with possible roles in delirium include acetylcholine, dopamine, serotonin, norepinephrine, glutamate and alpha-aminobutyric acid; so the contributing mechanisms disrupt the normal amounts and availability of one or more of these neurotransmitters thereby leading to delirium.
Hypoxia or Metabolic Derangement Can Cause Delirium
Hypoxia or metabolic derangements lead to impairment of brain metabolism and in turn causes decreased synthesis and release of one or more neurotransmitters. This neurotransmitter imbalance in turn leads to disruption of normal nerve transmission resulting in delirium.
Substances and Medications Can Induce a Delirium
Substances and medications that can induce a delirium include; alcohol, amphetamines, cocaine, LSD, marijuana, peyote, psilocybin, phencyclidine, Ambien, Lunesta, barbiturates, benzodiazepines, meprobamate, Soma, opiate pain pills, heroin, and others. The common mechanism appears to be disruption of neurotransmitter balance leading to disruption of normal nerve transmission eventuating in delirium.
Systemic Inflammation Can Induce a Delirium
Inflammation releases cytokines, which are signaling molecules used extensively in intercellular communication, causing neurotransmitter imbalance and disruption of nerve transmission. Trauma, infection or surgery can lead to increased production of proinflammatory cytokines causing severe inflammation and impart a direct neurotoxic effect in the brain. Research has demonstrated that proinflammatory cytokine levels have been shown to be elevated in patients with delirium.
In addition, low-grade inflammation associated with chronic neurodegenerative changes in the brains of patients with dementia might explain why these individuals are at an increased risk for developing delirium.
The Acute Stress Response Can Induce a Delirium
High levels of cortisol associated with acute stress have been hypothesized to precipitate and/or sustain delirium. In elderly patients, feedback regulation of cortisol is often impaired, resulting in higher levels of baseline cortisol and thereby predisposing this population to delirium. Additionally, a number of studies have identified elevated levels of cortisol in people who developed postoperative delirium.
Duration of Delirium
The duration of delirium is typically affected by the underlying cause.
Treatment of Delirium
Treatment of delirium requires treatment of the underlying cause, and delirium can initiate a cascade of events that lead to a downward spiral of functional decline, loss of independence, institutionalization, and, ultimately, death.