Delirium

Delirium is a disturbance of consciousness characterized by
acute onset and fluctuating course of inattention accompanied
by either a change in cognition or a perceptual disturbance, so
that a patient’s ability to receive, process, store, and recall
information is impaired.
Delirium, a medical emergency, develops rapidly over a short
period of time, is usually reversible, and is a direct consequence
of a medical condition or a brain insult. Many delirious ICU
patients have recently been comatose, indicating a fluctuation of
mental status. Comatose patients often, but not always, progress
through a period of delirium before recovering to their baseline
mental status.
ICU delirium is a predictor of increased mortality, length of
stay, time on ventilator, costs, re-intubation, long-term cognitive
impairment, and discharge to long-term care facility; it
necessitates special attention, assessment and management.
Delirium assessment is actually an important part of the overall
assessment of consciousness.
Delirium includes three subtypes: hyperactive, hypoactive and
mixed. Hyperactive delirium is characterized by agitation,
restlessness, and attempts to remove tubes and lines. Hypoactive
delirium is characterized by withdrawal, flat affect, apathy,
lethargy, and decreased responsiveness. Mixed delirium is
characterized by fluctuation between the hypoactive and
hyperactive. In ICU patients mixed and hypoactive are the most
common, and are often undiagnosed if routine monitoring is not
implemented. Few ICU patients (less than 5%) experience purely
hyperactive delirium.
The Confusion Assessment Method (CAM) was created in 1990
by Sharon Inouye, and was intended to be a bedside assessment
tool usable by non-psychiatrists to assess for delirium (Inouye
1990). The CAM-ICU is an adaptation of this tool for use in ICU
patients (e.g., critically ill patients on and off the ventilator who
are largely unable to talk).