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Delirium in ICU


Delirium is a common problem in the critically ill, affecting between 60-80% of mechanically ventilated patients. The importance of trying to prevent and when present, treat this condition, has only recently been appreciated.


Delirium is a form of organ dysfunction affecting the brain, in much the same way as shock represents dysfunction of the cardiovascular system.

Core features of delirium:

1. A disturbance of consciousness (i.e. reduced awareness of the environment, with reduced ability to focus, sustain or shift attention)

2. A change in cognition (i.e. impaired problem solving or memory) or a perceptual disturbance

3. Onset within hours or days, with a tendency to fluctuate.

Other common features include:

  • Intrusive abnormalities of awareness and affect, such as hallucinations (usually visual)
  • Inappropriate emotional states.


Delirium is a syndrome with a wide range of presentations. Three subtypes of delirium are recognised:

1. Hyperactive delirium: Only 5-22% of such patients

2. Hypoactive delirium

3. Mixed delirium with fluctuation between hyperactive and hypoactive forms.


The hypoactive form is commonly overlooked unless appropriate testing is undertaken.

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