Chest
Recent Advances in Chest MedicineLong-term Neurocognitive Function After Critical Illness
Section snippets
PREVALENCE AND NATURE OF CHRONIC NEUROCOGNITIVE IMPAIRMENTS
Medical and surgical management of critical illnesses can, and frequently does, result in de novo neurocognitive impairments. Research is limited regarding neurocognitive outcomes in survivors of critical illness; however, these patients are at risk for delirium (eg, acute cerebral dysfunction) during ICU treatment and chronic neurocognitive impairments.11, 12, 13, 14, 15 Early reports of chronic neurocognitive impairments after critical illness have been concerning, although additional
DURATION OF THE NEUROCOGNITIVE IMPAIRMENTS
Many critically ill patients have significant chronic neurocognitive impairments at 2 months,17 6 months,18, 24 9 months,21 1 year,16, 19, 23 2 years,28 and up to 6 years.20, 25 Neurocognitive impairments improve during the first 6 to 12 months post-hospital discharge. For example, 70% of ARDS survivors had neurocognitive impairments at hospital discharge, but only 45% had neurocognitive impairments at 1 year. There was no additional improvement in neurocognitive sequelae from the 1-year
REMOTE ASSESSMENT OF NEUROCOGNITIVE FUNCTION
A more complete understanding of the neurocognitive impairments following critical illness will require larger samples. Such studies may be hampered by the difficulties of performing in-person neurocognitive assessments in large multicenter studies or where face-to-face neurocognitive testing is impossible or impractical (such as in centers with a large geographic referral area). A 2004 study26 assessed neurocognitive function in ARDS survivors using questionnaires and tests administered over
Clinical Variables
A consistent finding across investigations is that no associations were found between some indicators of illness severity and the development of neurocognitive impairment or unfavorable neurocognitive outcomes. ICU length of stay, acute physiology and chronic health evaluation (APACHE) II scores, duration of mechanical ventilation, tidal volume, or number of days receiving sedative, narcotic, or paralytic medications were not associated with neurocognitive impairments in critically ill patients.
LACK OF RECOGNITION OF COGNITIVE IMPAIRMENTS
A recent study28 found that 42% of ARDS survivors underwent rehabilitation therapy, but most were not evaluated for neurocognitive impairments, with only 12% identified as having neurocognitive impairments by the clinical rehabilitation team. Neurocognitive impairments appear to be underrecognized by both ICU and rehabilitation providers. Studies have suggested that in non-ICU clinical settings many physicians fail to recognize (or assess) neurocognitive impairment in 35 to 90% of patients.38
CONSEQUENCES OF CHRONIC NEUROCOGNITIVE IMPAIRMENTS
The consequences of chronic neurocognitive impairments are far-reaching and typically contribute to a decreased ability to perform activities of daily living, decreased quality of life, increased medical costs, and the inability to return to work. Two years after hospital discharge, 34% of ARDS survivors were working or were full-time students, 34% were receiving disability payments that started after hospital discharge for ARDS, and 32% patients (20 of 62 patients) were not working or were
POTENTIAL MECHANISMS OF NEUROCOGNITIVE IMPAIRMENTS
There is probably not a single uniform cause of neurocognitive impairments, but rather a number of more or less significant factors that interact dynamically with premorbid variables and result in adverse outcomes (Figure 4). Data regarding the potential mechanisms of neurocognitive impairments are limited, but possible mechanisms may include hypoxemia,16 the use of sedatives or analgesics,51 hypotension,19 delirium,52 and hyperglycemia.18 The degree and duration of hypoxemia were modestly
CONCLUSIONS
The investigation of neurocognitive function after critical illness is in its infancy, with a small number of investigations in existence documenting both the presence of de novo neurocognitive impairment in a significant percentage of ICU survivors without preexisting deficits and the worsening of neurocognitive impairment in individuals who were previously impaired. It has been widely recognized that the physical consequences of critical illness are far-reaching and sometimes permanent,
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