Acute Confusional Syndrome: Symptoms, Types, and Treatment

26 October, 2020
Have you heard of acute confusional syndrome, otherwise known as delirium? Where does the term come from, and what causes it? We'll answer those questions and more in today's article.

Have you ever heard of acute confusional syndrome (ACS)? Also known as delirium, ACS is a neurocognitive disorder that affects approximately one to two percent of the general population and about 14 percent of adults over the age of 85. Its primary characteristic is an alteration in consciousness accompanied by a decrease in attentional capacity and other cognitive changes that affect memory, language, and perception. As its name suggests, it’s an acute condition that usually lasts hours or days and then completely disappears.

As you’ll learn in this article, the potential causes of acute confusional syndrome are varied but of mostly organic origin. They include certain medications, illnesses, intoxication, or abstinence from certain substances.

ACS is pathogenic, which means that the symptoms tend to be the same no matter what the cause. Ready to delve deeper? Keep reading.

An elderly woman with her hands on her head.

Acute confusional syndrome or delirium: the beginning

What we know today as ACS or delirium has been recognized since ancient times. Hippocrates originally described the condition in writing and Celsus was the first to use the term “delirium” in documents that date back to 1st century BC.

In 1813, Thomas Sutton described a more specific clinical syndrome, delirium tremens, which was triggered by alcohol consumption. Later, Emil Kraepelin proposed that each somatic disorder had specific related mental syndromes.

In 1910, Bonhoeffer described five syndrome groups or clinical variations that were acute during the course of different illnesses. Those groups were delirium, amentia, a twilight state (or epileptic type), excitement, and acute hallucinosis.

What’s acute confusional syndrome?

According to the DSM-5 (2013), delirium affects one to two percent of the general population. The prevalence increases with age, topping out at 14 percent of individuals over 85. It also affects 10 to 30 percent of hospitalized patients. Research shows that, among the older adult population, men have a higher risk of developing ACS than women.

The DSM-5 (Diagnostic and Statistical Manual of Mental Disorders) classifies ACS within the category of neurocognitive disorders. As we mentioned above, delirium has many potential triggers, which is why the DSM-5 has identified five distinct types:

  • Substance intoxication delirium.
  • Substance withdrawal delirium.
  • Medication-induced delirium.
  • Delirium due to other medical conditions.
  • Delirium due to multiple etiologies.

The DSM-5 also includes certain specifications for delirium. In terms of duration, delirium can be acute (lasting hours or days) or persistent (lasting weeks or months). In terms of activity level, delirium can be hyperactive, hypoactive, or mixed. Health professionals add these specifications to the delirium diagnosis.

Types of ACS or delirium

The DSM-5 divides the types of delirium into subtypes defined by their etiology. They are:

  • Substance intoxication delirium. Different substances can cause delirium. They include alcohol, hallucinogenics, amphetamines and related substances, cannabis, cocaine, phencyclidine and related substances, inhalants, opioids, sedatives, hypnotics, and anxiolytics, among others.
  • Substance withdrawal delirium. In this case, the cause is abstinence, not intoxication, from certain substances. These include alcohol (alcohol withdrawal causes delirium tremens), sedatives, hypnotics, and anxiolytics, among others.
  • Medication-induced delirium. Most medications have the potential to trigger acute confusional syndrome. These include anesthetics, analgesics, antiasthmatics, anticonvulsants, antihistamines, cardiovascular and hypertension medication, antimicrobials, medication for Parkinson’s disease, corticosteroids, gastrointestinal medication, muscle relaxers, and psychotropics with anticholinergic side effects. In addition, toxins can also cause delirium. They include volatile substances (gasoline or paint, for example), insecticides, and carbon dioxide.
  • Delirium due to other medical conditions. The reality is that practically any internal medical illness can cause delirium.
  • Delirium due to multiple etiologies. Lastly, when more than one cause would explain the condition, doctors call it delirium due to “multiple etiologies”.

The ICD-10 (International Classification of Diseases) definition

The WHO also provides a description of delirium or ACS in the ICD-10. It includes the following characteristics:

  • A decline in awareness and attention.
  • General cognitive disorder.
  • Psychomotor disorders (hypo or hyperactivity, unexpected changes from one state to another).
  • Sleep disorders (insomnia and daytime sleepiness).
  • Emotional disorders.

Generic characteristics

The common characteristics of acute confusional syndrome are the following:

  • Pathogenic identify. As we mentioned above, this means that patients with ACS all have similar clinical presentations independently of the cause of their condition.
  • Sudden onset. ACS can develop over the course of a few hours or days.
  • More or less intense repercussions on the person’s general state. This is a comprehensive disorder.
  • Relatively short duration (which is why it’s called an “acute” disorder).
  • Complete recovery is possible.
  • There can be fluctuations in symptoms over the course of the day.
An older man with his hands on his face.

Treatment for ACS/delirium

The treatment for ACS involves fixing whatever issue triggered it in the first place. Thus, the point of intervention is to quickly reverse the disorder to make sure it doesn’t become more serious.

On the other hand, the potential complications of delirium can be prevented through a series of interventions. Also, medical professionals can take some general measures to reduce the risks for people with risk factors, such as avoiding sudden environmental changes for the elderly and preventing complications (accidents, infections, etc.).

  • American Psychiatric Association -APA- (2014). DSM-5. Manual diagnóstico y estadístico de los trastornos mentales. Madrid. Panamericana.
  • American Psychiatric Association -APA- (2000). DSM-IV-TR. Diagnostic and statistical manual of mental disorders (4thEdition Reviewed). Washington, DC: Author.
  • OMS: CIE-10. (1992). Trastornos Mentales y del Comportamiento. Décima Revisión de la Clasificación Internacional de las Enfermedades. Descripciones Clínicas y pautas para el diagnóstico. Organización Mundial de la Salud, Ginebra.