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  • Delirium may be considered to be present when there is an acute or fluctuating change in mental status and inattention coupled to disordered thinking or an altered level of consciousness.
  • Delirium is extraordinarily common among patient populations in the intensive care unit (ICU) and is under-recognized by care providers, in part related to a previous lack of tools to assess this phenomenon.
  • Hypoactive or mixed forms of delirium are more common than pure hyperactive delirium.
  • The Confusion Assessment Method for the ICU is a well-validated tool to provide simple and reproducible assessment of delirium at the bedside.
  • The risk factors for delirium may be divided into host factors, the acute illness, and environmental or iatrogenic factors.
  • Because age and pre-existing mental impairment are powerful risk factors for delirium, it is likely to be encountered with increasing frequency in the ICU in the future.
  • Because administration of psychoactive drugs, including sedatives and analgesics, is an important risk factor for delirium, this represents a fruitful area for modification of practice to reduce the incidence of delirium in ICU patients.
  • Delirium is independently associated with increased morbidity, cost of care, and mortality rate, even after adjusting for severity of illness, age, coma, and other relevant covariates.


Patients in the intensive care unit (ICU) who experience delirium are exhibiting an under-recognized form of organ dysfunction. Delirium is extremely common in ICU patients due to factors such as comorbidity, critical illness, and iatrogenesis. This neurologic complication can be extremely hazardous in hospitalized older persons and is associated with death, prolonged hospital stays, and institutionalization. Neurologic dysfunction compromises patients' ability to be removed from mechanical ventilation or achieve full recovery and independence. Unfortunately, health care providers in the ICU are unaware of delirium in many circumstances, especially those in which the patient's delirium is manifesting predominantly as the hypoactive (quiet) subtype as opposed to the hyperactive (agitated) subtype. In the past few years, research on ICU delirium has demonstrated the importance of this problem in critically ill patients in addition to methods for routinely monitoring delirium at the bedside. This chapter reviews the definition and salient features of delirium, its primary risk factors, validated methods for bedside delirium assessment, pharmacologic agents associated with the development of delirium, and pharmacologic and nonpharmacologic strategies for delirium management.


Historically, two words were used to describe confused patients. One was the Roman word delirium, which referred to an agitated and confused person (think of hyperactive delirium). The other was from the Greek word lethargus, which was used to describe a quietly confused person (think of hypoactive delirium). ICU patients commonly demonstrate both subtypes as they progress through different stages of their illness and therapy. In either case, the patient's brain is not functioning normally. It therefore makes sense that the original derivation of delirium comes from the Latin word deliria, which literally means to “be out of your furrow.” For greater clarity and to avoid misuse of ...

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