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  • Critically ill patients are at great risk for delirium. This organ dysfunction is grossly underrecognized and undertreated. Delirium is mistakenly thought to be transient and expected.

  • Delirium is an independent risk factor for prolonged length of stay and higher 6-month mortality. Many ICU survivors demonstrate persistent cognitive impairment at follow-up testing months to years later.

  • Clinicians must be able to recognize delirium readily at the bedside. The CAM-ICU is a valid, reliable, quick, and easy-to-use serial assessment tool for monitoring delirium in ventilated and nonventilated ICU patients.

  • Delirium is a multifactorial problem for ICU patients that demands an interdisciplinary approach for assessment, management, and treatment.

  • Most pharmacologic strategies to treat delirium have been unsuccessful. Bundled care practices, such as the ABCDEF Bundle, are the mainstay of prevention and treatment of delirium in critically ill patients.


Intensive care unit (ICU) patients with delirium suffer from an often underrecognized form of acute organ dysfunction. Delirium is common in critically ill patients as factors such as comorbidities, the acute critical illness itself, and iatrogenesis intersect to create a high-risk setting for delirium. This neurologic complication often portends poor outcomes, being associated with death, prolonged hospital stays, increased costs, long-term cognitive impairment, and institutionalization. Delirium compromises patients’ ability to be removed from mechanical ventilation, to fully recover from their acute illness, and to regain independence. Clinicians in the ICU may be unaware of delirium in certain circumstances, especially those in which the patient’s delirium manifests predominantly as the hypoactive (quiet) subtype rather than the hyperactive (agitated) subtype. Despite being often overlooked, delirium during critical illness has been the focus of two decades of research, which has brought to light the scope of the problem and has provided clinicians with tools for monitoring delirium at the bedside. This chapter reviews the definition and salient features of delirium, different subtypes, its primary risk factors, including drugs associated with the development of delirium, proposed pathophysiologic mechanisms, validated methods for bedside delirium assessment, and nonpharmacologic and pharmacologic strategies for delirium management.


The American Psychological Association’s (APA) Diagnostic and Statistical Manual of Mental Disorders (DSM)-V describes delirium as a disturbance in attention and cognition that develops over a short period of time (eg, hours to days) and tends to fluctuate during the course of the day.1 There are five criteria required to diagnose delirium:

  1. A disturbance in attention (ie, reduced ability to direct, focus, sustain, and shift attention) and awareness (reduced orientation to the environment).

  2. The disturbance develops over a short period of time (usually hours to a few days), represents a change from baseline attention and awareness, and tends to fluctuate in severity during the course of a day.

  3. An additional disturbance in cognition (eg, memory deficit, disorientation, language, visuospatial ability, or perception).

  4. The disturbances in Criteria 1 and 3 are ...

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