Short- and Long-Term Cognitive Outcomes in Intensive Care Unit Survivors

https://doi.org/10.1016/j.ccm.2008.11.001Get rights and content

Evidence increasingly suggests that cognitive impairment is common in intensive care unit survivors, although the nature, severity, and natural history remain unclear. Although the cognitive impairments improve over time in some individuals, they often fail to completely abate. While the functional correlates of these impairments are under-studied, cognitive impairments may adversely impact quality of life, ability to return to work or to work at previously established levels, and ability to function effectively in emotional and interpersonal domains. The potential etiologies of cognitive impairments in intensive care unit survivors are not fully understood and are likely heterogeneous and vary widely across patients. The contributions of these many factors may be particularly significant in patients with pre-existing vulnerabilities for the development of cognitive impairments, such as mild cognitive impairment, dementia, prior traumatic brain injury, or other comorbid disorders, as well as predisposing genetic factors.

Section snippets

Delirium or short-term cognitive outcomes

Delirium is a neurobehavioral syndrome that occurs across health care settings, is associated with adverse outcomes, including death,1, 2 and is the most common manifestation of acute brain dysfunction during critical illness and among mechanically ventilated ICU cohorts.2 Although many view delirium as transient, neuropathologic abnormalities are observed on brain imaging in delirious patients, including ventricular enlargement, and generalized and cortical and subcortical lesions.3, 4 A

Prevalence of cognitive dysfunction

Cognitive impairment is generally long-lasting (observed as late as 6 years after ICU discharge) and is experienced among large numbers of ICU survivors. Among general medical ICU survivors, approximately one-third or more have long-term cognitive impairment.22 It is difficult to determine the extent to which this impairment represents a new condition or reflects a worsening of an already existing impairment, as baseline data on cognitive functioning is generally unavailable in critically ill

Duration of cognitive impairments

In general, it appears that the majority of ICU survivors experience marked improvement in cognitive functioning in the first 6 to 12 months after hospital discharge. However, despite demonstrating a clear trajectory of improvement, many individuals continue to demonstrate persistent neuropsychologic difficulties over time, infrequently returning to their pre-ICU baseline levels. For example, 70% of ARDS survivors had cognitive impairments at hospital discharge but only 45% had cognitive

Mechanisms of cognitive impairments

It was once believed that the brain was protected from most insults because of the existence of the blood-brain barrier and central autoregulation. It is now recognized that the brain is immunologically active and therefore vulnerable to systemic inflammatory reactions, such as those resulting from sepsis or septic shock, similar to the findings in severe systemic illness. The inflammatory responses are mediated by cytokines, nonantibody proteins that penetrate the blood-brain barrier directly

Functional implications of cognitive impairments

While knowledge regarding cognitive morbidity following critical illness is increasing, few studies have assessed the impact of cognitive impairments on patients' functional outcomes. The functional effects of cognitive impairments may be far reaching, including permanent disability or inability to return to work. Cognitive impairments can render individuals unable to perform basic activities of daily living (ADLs), such as feeding, dressing, and bathing. Declines in instrumental activities of

Assessment of pre-illness cognitive function

Perhaps the one of the most methodologically challenging issue in the study of cognitive outcomes in ICU survivors is the assessment of premorbid neuropsychologic functioning.66 As critically ill patients typically experience an acute onset of illness, it is rarely possible to evaluate them before hospitalization. Therefore, methods of estimating pre-illness cognitive functioning must be employed, especially because many patients have multiple comorbid chronic medical disorders. Assessment

Cognitive rehabilitation and follow-up clinics

ICU survivors not only demonstrate high rates of cognitive impairment as measured by neuropsychologic testing, but they also subjectively report the presence of diminished cognitive abilities, as well as persistent difficulties with memory, concentration, and planning and organizing. Cognitive impairments appear to be under-recognized by both ICU and rehabilitation providers. In non-ICU clinical settings, physicians fail to recognize (or assess) cognitive impairment in 35% to 90% of patients.71

Summary

The significant and sometimes permanent effects of critical illness on cognitive functioning are increasingly recognized, so that a virtual consensus now exists among the intensive care community regarding the importance of this issue. Since the presence of cognitive impairment among medical ICU survivors was first systematically identified a decade or so ago, much progress has been made to study and better characterize this phenomenon. In the intervening years, we have learned that cognitive

References (80)

  • P.P. Pandharipande et al.

    Effect of sedation with dexmedetomidine vs lorazepam on acute brain dysfunction in mechanically ventilated patients: the MENDS randomized controlled trial

    JAMA

    (2007)
  • H. Koponen et al.

    Computed tomography findings in delirium

    J Nerv Ment Dis

    (1989)
  • M.R. Suchyta et al.

    Brain MR and CT findings associated with critical illness

    Proc Am Thorac Soc

    (2005)
  • Z.J. Lipowski

    Delirium in the elderly patient

    N Engl J Med

    (1989)
  • P. Galanakis et al.

    Acute confusional state in the elderly following hip surgery: Incidence, risk factors and complications

    Int J Geriatr Psychiatry

    (2001)
  • S.T. O'Keefe et al.

    Postoperative delirium in the elderly

    Br J Anaesth

    (1994)
  • E.W. Ely et al.

    Delirium in mechanically ventilated patients: validity and reliability of the confusion assessment method for the intensive care unit (CAM-ICU)

    JAMA

    (2001)
  • E.W. Ely et al.

    Delirium as a predictor of mortality in mechanically ventilated patients in the intensive care unit

    JAMA

    (2004)
  • S.K. Inouye et al.

    Does delirium contribute to poor hospital outcomes? A three-site epidemiologic study

    J Gen Intern Med

    (1998)
  • Second International Study of Infarct Survival

    Randomised trial of intravenous streptokinase, oral aspirin, both, or neither among 17,187 cases of suspected acute myocardial infarction: ISIS-2

    Lancet

    (1988)
  • K.K. Uldall et al.

    Association between delirium and death in AIDS patients

    Aids Patient Care STDS

    (2000)
  • P. Eikelenboom et al.

    Do delirium and Alzheimer's dementia share specific pathogenetic mechanisms?

    Dement Geriatr Cogn Disord

    (1999)
  • J.C. Jackson et al.

    The association between delirium and cognitive decline: a review of the empirical literature

    Neuropsychol Rev

    (2004)
  • M.M. Dolan et al.

    Delirium on hospital admission in aged hip fracture patients: prediction of mortality and 2-year functional outcomes

    J Gerontol A Biol Sci Med Sci

    (2001)
  • M.P. Lawton et al.

    Assessment of older people: self-maintaining and instrumental activities of daily living

    Gerontologist

    (1969)
  • J. Francis et al.

    Prognosis after hospital discharge of older medical patients with delirium

    J Am Geriatr Soc

    (1992)
  • J. McCusker et al.

    Delirium in older medical inpatients and subsequent cognitive and functional status: a prospective study

    Can Med Assoc J

    (2001)
  • T. Rahkonen et al.

    Delirium in the non-demented oldest old in the general population: risk factors and prognosis

    Int J Geriatr Psychiatry

    (2001)
  • K. Rockwood et al.

    The risk of dementia and death after delirium

    Age Ageing

    (1999)
  • H. Koponen et al.

    Delirium among elderly persons admitted to a psychiatric hospital: clinical course during the acute stage and one-year follow-up

    Acta Psychiatr Scand

    (1989)
  • J.C. Jackson et al.

    Six-month neuropsychological outcome of medical intensive care unit patients

    Crit Care Med

    (2003)
  • R.O. Hopkins et al.

    Neuropsychological sequelae and impaired health status in survivors of severe acute respiratory distress syndrome

    Am J Respir Crit Care Med

    (1999)
  • Hopkins RO, Jackson JC, Wallace CJ. Neurocognitive impairments in ICU patients with prolonged mechanical ventilation....
  • R.O. Hopkins et al.

    Quality of life, emotional, and cognitive function following acute respiratory distress syndrome

    J Int Neuropsychol Soc

    (2004)
  • M.R. Suchyta et al.

    The incidence of cognitive dysfunction after ARDS

    Am J Respir Crit Care Med

    (2004)
  • K.T. Sukantarat et al.

    Prolonged cognitive dysfunction in survivors of critical illness

    Anaesthesia

    (2005)
  • K. Marquis et al.

    Neuropsychological sequelae in survivors of ARDS compared with critically ill control patients

    Am J Respir Crit Care Med

    (2000)
  • F. Al-Saidi et al.

    Neuropsychological sequelae in ARDS survivors

    Am J Respir Crit Care Med

    (2003)
  • J.C. Jackson et al.

    Acute respiratory distress syndrome and long-term cognitive impairment: A case study

    Arch Clin Neuropsychol

    (2003)
  • C. Jones et al.

    Significant cognitive dysfunction in non-delirious patients identified during and persisting following critical illness

    Intensive Care Med

    (2006)

    • Cited by (0)

    View full text
    Copyright © 2009 Elsevier Inc. All rights reserved.