Delirium - Types, Causes, Symptoms, Signs, Diagnosis, Treatment


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What is Delirium?

"Mental health needs a great deal of attention. It’s the final taboo and it needs to be faced and dealt with." - Adam Ant

Delirium is a sudden disturbance in mental function that causes confusion and decreased awareness of one’s environment.

Delirium, or acute confusional state, is a sudden, severe and serious disturbance in brain function that results in confusion, decreased awareness of one’s environment, and impaired focus. Although delirium can occur in any age group, it is most common in the elderly. It is not a disease per se, but a syndrome of similar symptoms that can be caused by various ailments. These symptoms associated with delirium typically fluctuate during the course of illness. Delirium is very common in the ICU and during palliative care and can be fatal if not picked up early, so prompt diagnosis and management is of utmost importance.


Types of Delirium

Delirium is typically classified into 3 subtypes: hyperactive, hypoactive and mixed. Some special scenarios also exist, such as delirium tremens, excited delirium, post-operative delirium etc.


In this type of delirium, patients are agitated, aggressive and frequently hallucinate; Up to 22% of patients with delirium have the hyperactive type.


Up to 50% of delirium cases may be hypoactive. This type of delirium is characterized by a state of reduced awareness of surroundings, decreased muscle movements, lethargy, indifference and neglect of things happening around, which can often be mistaken for depression. It is necessary to properly diagnose this state, because it has a higher rate of mortality than hyperactive delirium.


The mixed form of delirium exhibits features of both of the above states, often in a fluctuating manner.

Excited Delirium

Excited delirium is a unique form of acute delirium that usually occurs in drug abusers. It manifests as sudden onset of bizarre behaviour, fear, paranoia, aggression and sudden death. Patients in excited delirium often feel the urge to indulge in violent activities, resulting in being apprehended by the law. Excited delirium is still under investigation and the molecular reasons behind it are being studied.

Excited Delirium

ICU Delirium

Up to 80% of patients admitted in the ICU may have delirium. ICU delirium occurs due to various causes, as most patients in the ICU already have severe medical and/or surgical conditions. It may manifest as any of the three forms of delirium.

Delirium Tremens

Delirium tremens (alcohol withdrawal delirium) is caused because of withdrawal of alcohol in people who have become dependent on it. It can also be caused by concurrent infection or illness in alcoholics. It commonly manifests as tremors, agitation and confusion.

Delirium Tremens

Operation Related Delirium

There are many reasons for delirium occurring before, during or after an operation. These include:
  • Before operation: Pre anaesthetic medications, electrolyte imbalance
  • During operation: Sedatives, opioids, anticholinergics
  • After the operation: Low BP, low oxygen levels, withdrawal effect of medications
  • Post-operative psychosis:
    Depression, hallucination, mania, impulsivity, loss of understanding of reality may occur in people following surgery, collectively called post-operative psychosis. This is a major cause of hospitalization, but the reasons and pathology behind it are poorly identified till date.

Causes of Delirium

Delirium can be caused by substance abuse or withdrawal, or due to general medical conditions.

The common causes of delirium include:
  • Infections such as meningitis, encephalitis, septicaemia etc
  • Stroke
  • Metabolic problems
  • Medication related:
    • Anticholinergic such as atropine, commonly used to treat organophosphorus poisoning
    • Sedatives
    • Opioids
    • Centrally acting anti-hypertensives
    • Anti-allergy medication
    • Steroids
    • Anti Parkinson’s treatment such as levodopa

    Causes of Delirium

  • Post operative state
  • Deficiency of glucose in the blood
  • Hypoxia or deficiency of oxygen in the blood
  • Substance abuse, such as alcohol, cannabis, heroin etc.
  • Alcohol withdrawal delirium – also called delirium tremens
  • Sleep deprivation
  • Structural problems in the brain
  • Severe vitamin deficiencies
  • Heart, liver, kidney or thyroid failure
  • After seizures
Causes of Hypoactive Delirium:
  • Hypoxia
  • Metabolic disturbances
  • Anticholinergic medication
Causes of Hyperactive Delirium:
  • Alcohol withdrawal
  • Drug intoxication
  • Medication related

Risk Factors of Delirium include:
  • Use of physical restraints
  • Malnutrition
  • Catheterization of the bladder
  • Any treatment-related event
  • Use of 3 or more medications
  • Related psychiatric disorder
  • Old age

Signs and Symptoms of Delirium

The signs and symptoms of delirium are many and may vary with the type of delirium, but they can generally be said to be as they are listed below:

Main Symptoms

  • Change of the level of consciousness – Consciousness level may be highest during the morning and may worsen during the night – called the “sundowning” phenomenon
  • Difficulty in maintaining attention
  • Changes in feeling and perception
  • Disorientation to time, place and person
  • Illusions
  • Hallucinations


  • Altered behaviour
  • Changes in movement – depending on the subtype of delirium
  • Incoherent, irrelevant speech
  • Tremors (particularly in delirium tremens)
  • Cloth picking behaviour
  • Emotional changes – patients with delirium may go through the whole gamut of emotions in a short time
  • An inner feeling of restlessness, manifested outside as restless movements of the body

Diagnosis of Delirium

The diagnosis of delirium is purely clinical. Many clinical scoring systems are available to aid in the diagnosis. It is important to differentiate delirium from dementia.

The diagnosis of delirium is purely clinical. It is not detected by any laboratory test or radiological investigation. A thorough clinical examination focussing on the central nervous system, which includes testing for movements, sensations and higher functions, is imperative to arrive at the diagnosis. There are a few tools which make it easier to diagnose delirium, such as:
  • Confusion Assessment Method
  • Delirium Symptom Interview
  • Delirium rating scale
  • Memorial Delirium Assessment Scale
  • DSM 5 criteria
The DSM V criteria provide the cornerstone in diagnosing delirium. These include:
  • Disturbance of consciousness
  • Change in cognition that is not due to dementia.
  • Sudden onset, fluctuating disturbance
  • Evidence from the clinical examination or laboratory testing that it is caused by a direct consequence of a general medical condition, an intoxicating substance, medication use, or more than one cause.
Although laboratory investigations cannot diagnose delirium, they may be helpful in finding out the cause of delirium or to rule out alternative diagnoses. Some of the laboratory tests that may be helpful are:

Blood investigations:
  • Complete metabolic profile
  • Blood ammonia level
  • ABG (arterial blood gas)
  • Toxicology screening for alcohol and recreational drugs
  • Liver function tests
  • Kidney function tests
  • Thyroid function tests
  • Magnesium and other electrolytes
  • Vitamin levels in the blood
Other investigations that may be useful are:
  • Chest X ray
  • CT scan of the brain
  • MRI scan of the brain
  • EEG (Electro Encephalogram)

Electro Encephalogram

  • Lumbar Puncture and CSF analysis
  • Mental Status Tests
  • Urine analysis
It is necessary to differentiate between delirium and dementia, as one may masquerade as the other. Dementia is a chronic, mostly irreversible, progressive disease occurring over months and years, that severely affect the daily functioning of patients due to loss of ability to think, reason or control their emotions clearly. It is associated with a chronic degeneration of the brain. There are many types of dementia, which include:
  • Alzheimer’s disease
  • Vascular dementia (multi-infarct dementia)
  • Lewy body dementia
  • Fronto temporal dementia, and others

Treatment for Delirium

The treatment of delirium involves both supportive therapy and pharmacological therapy.

The treatment of delirium basically depends on identifying the cause of delirium and treating it. Treatment may be broadly categorized into two complementing methods of care:

Supportive therapy

  • Monitoring of the patient’s fluid and nutrition status and treating accordingly
  • Reorientation methods
  • Avoiding Physical Restraints correction of sensory deficits
  • Behaviour modification
  • Psychiatric consultation

Psychiatric Consultation

Pharmacologic therapy

  • Neuroleptics (Also called antipsychotics)
    • Haloperidol
    • Risperidone
    • Olanzapine etc
  • Sedatives (short acting)
    • Lorazepam
    • Midazolam
  • Cholinesterase inhibitors
    • Donepezil
  • Thiamine, which is mostly prescribed for alcohol withdrawal delirium
  • Vitamin B 12, if its deficiency is identified
  • Antidepressants
  • Specific therapy for the underlying cause

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