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756 PART 6: Neurologic Disorders

CHAPTER Delirium in the Intensive TABLE 82-1 Differentiating Delirium From Dementia
82 Care Unit Onset Delirium Dementia
Acute (hours to days)
Insidious (months to years)
Nathan E. Brummel Course Fluctuating Progressive
Timothy D. Girard
Diagnostic • Impaired ability to focus, shift • Memory impairment plus one
Features or sustain attention of the following:
INTRODUCTION • Change in cognition (eg, memory • Aphasia
Patients in the intensive care unit (ICU) who experience delirium are impairment, disorientation • Apraxia
exhibiting an under-recognized form of organ dysfunction. Delirium is or language) or development in • Agnosia
https://kat.cr/user/tahir99/
extremely common in ICU patients as factors such as comorbidity, the perceptual disturbances • Impaired executive functioning
acute critical illness itself, and iatrogenesis intersect to create a high-risk • Fluctuating course • Impairments must be severe
setting for delirium. This neurologic complication is often hazardous, enough to cause impairments
being associated with death, prolonged hospital stays, and long-term in social or occupational
cognitive impairment and institutionalization. Neurologic dysfunction functioning and represent
compromises patients’ ability to be removed from mechanical ventila- a decline from baseline
tion or to fully recover and regain independence. Unfortunately, health Associated • Sleep/wake disturbances • Visuospatial impairment
care providers in the ICU are unaware of delirium in many circum- Features • Extremes in psychomotor activity • Little/no awareness of memory
stances, especially those in which the patient’s delirium is manifesting • Emotional disturbances (fear, impairment
predominantly as the hypoactive (quiet) subtype rather than the hyper- anxiety, depression, irritability, • Gait disturbances (falls)
active (agitated) subtype. Despite being often overlooked clinically, ICU euphoria, apathy) • Anxiety/mood/sleep
delirium has increasingly been the subject of research during the past disturbances
decade, which has brought to light the scope of the problem in critically Common • Acute medical illness • Dementia of Alzheimer type
ill patients and provided clinicians with tools for routinely monitoring Causes • Medication/substance/toxin • Vascular dementia
delirium at the bedside. This chapter reviews the definition and salient ingestion or withdrawal • Chronic medical conditions
features of delirium, its primary risk factors, including drugs associated • Multifactorial (eg, Pick disease, HIV, stroke,
with the development of delirium, proposed pathophysiologic mecha- head injury)
nisms, validated methods for bedside delirium assessment, and nonphar-
macologic and pharmacologic strategies for delirium management. Data from American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders. 4th ed.
Text Revision. Washington, D.C.: American Psychiatric Association; 2000.
2-5
DEFINITION AND TERMINOLOGY subacute befuddlement, and toxic confusional state. Neurologists often
use “encephalopathy” to refer to hypoactive delirium and “delirium” to
The American Psychological Association’s (APA) Diagnostic and Statistical describe only hyperactive delirium. Among ICU practitioners, “delirium”
6
Manual of Mental Disorders (DSM)-IV describes delirium as a distur- is used inconsistently, as evidenced by a recent survey of Canadian inten-
bance in consciousness and cognition that develops over a short period sivists that found respondents were more likely to use the term “delirium”
of time (eg, hours to days) and tends to fluctuate during the course of the when no specific underlying etiology could be identified for a patient with
day. Specifically, there are four criteria required to diagnose delirium : 1 fluctuating mental status with inattention, perceptual changes, and disor-
1
1. Disturbance of consciousness, with reduced awareness of the envi- ganized thinking, whereas alternative terms (eg, hepatic encephalopathy)
5,7
ronment and impaired ability to focus, sustain or shift attention. were used when the etiology of delirium was obvious.
Increasingly, however, the ICU community is seeking to standardize
2. Altered cognition (eg, memory impairment, disorientation, or lan- delirium terminology to conform to the APA definition, with the hope that
guage disturbance) or the development of a perceptual disturbance use of “delirium” to describe this syndrome of acute brain dysfunction,
(eg, delusion, hallucination, or illusion) that is not better accounted regardless of etiology, will improve cross-talk between specialists with
for by preexisting or evolving dementia. different medical backgrounds, collaborative research efforts, and
3. Disturbance develops over a short period of time (usually hours to ultimately management of this widely prevalent syndrome. Therefore,
4
days) and tends to fluctuate during the course of the day. the unifying term “delirium” should be applied whenever patients meet
4. Evidence of an etiological cause, which the DSM-IV uses to classify DSM-IV diagnostic criteria for delirium, and the underlying etiology,
delirium as Delirium Due to a General Medical Condition, Substance- when known, can be used as an associated term (eg, “delirium secondary
Induced Delirium, Delirium Due to Multiple Etiologies, or Delirium to sepsis” is preferred over “septic encephalopathy”).
Not Otherwise Specified.
PREVALENCE AND SUBTYPES
Historically, two words were used to describe acutely confused patients.
The Roman word delirium referred to an agitated and confused person Delirium during critical illness occurs in 20% to 80% of ICU patients
(ie, hyperactive delirium). The Greek word lethargus was used to describe depending on the severity of illness of the population studied and meth-
a quietly confused person (ie, hypoactive delirium). ICU patients com- ods used to detect delirium. 8-16 The prevalence is highest, for example, in
monly demonstrate both subtypes of delirium as they progress through mechanically ventilated ICU patients, with 60% to 80% developing delir-
different stages of their illness and therapy. In both subtypes, the patient’s ium during their ICU stay, 8,10,12,14,17 whereas lower prevalence rates are
brain is not functioning normally. It therefore makes sense that the reported in nonventilated patients and in mixed ICU populations. 9,11,18
original derivation of delirium comes from the Latin word deliria, which In general, ICU patients have a higher prevalence of delirium compared
literally means to “be out of your furrow.” For greater clarity and to avoid with noncritically ill hospitalized patients. 19,20 The prevalence of ICU
misuse of terms such as dementia and delirium, Table 82-1 lists basic delirium will likely increase as the U.S. population ages.
definitions and clinical characteristics of each syndrome. Delirium can be subtyped based on observed changes in motor activ-
21
Delirium in the ICU has been referred to in the medical literature using ity, resulting in hypoactive, hyperactive, and mixed subtypes. Peterson
a multitude of terms, including ICU psychosis, ICU syndrome, brain et al reported these delirium subtypes in a cohort of 613 ventilated and
failure, encephalopathy, postoperative psychosis, acute organic syndrome, nonventilated ICU patients in whom delirium was monitored for more

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