Cognitive Assessments in Critical Care Patient Populations: Methodological Considerations

By Sachin Agarwal & Marykay Pavol
First Online: 20 January 2021

The high incidence of neuropsychological deficits after critical illnesses and their decisive impact on long-term recovery are well described in the literature [1,2,3]. Early cognitive testing after acute stabilization has been proposed as a method to elucidate risk factors for poor cognitive outcomes and identify opportunities for intervention such as early referral for cognitive therapy. Brief, efficient, and reliable neuropsychological assessment can be useful in clinical practice and research to quantify cognitive functioning in people with acute brain injury following intracranial or systemic insults. The National Institutes of Health Toolbox for the Assessment of Neurological and Behavioral Function Cognition Battery (NIHTB-CB) [4] is a computerized neuropsychological screening battery, which has been recommended as a common data element for brain injury research and clinical trials. Of note, all studies to date have been conducted with patients living in the community [5]. Assessment of hospitalized patients must consider issues related to delirium, ability to adhere to standardized administration, and the timing of examinations in relation to the date of injury/illness onset. Consequently, whereas bedside mental status examinations are commonly performed, formal cognitive assessment is less common in hospitalized patients [5]. Patients in the early stages of recovery from critical illness are at high risk of impairments in attention and stamina.

In the current issue of Neurocritical care, Maas et al. [6] performed a prospective, observational cohort study on 73 patients presenting with acute onset of either intracerebral hemorrhage (ICH; n = 38) or sepsis (n = 53) as representative neurologic and systemic critical illnesses. The NIHTB-CB and Patient-Reported Outcomes Measurement Information System (PROMIS) cognition measures were administered seven days after intensive care unit (ICU) discharge or at hospital discharge, whichever occurred first. PROMIS instruments for patient-reported cognitive evaluations were successfully obtained in 42 (58% overall; 79% of sepsis and 34% of ICH) patients, and scores were favorable (median was 97th percentile compared to the general adult population). Patients who completed PROMIS cognitive assessments differed from those who did not by having less severe encephalopathy in the early phase of critical illness and at the time of hospital discharge. Testable patients had shorter ICU length of stay, less severe functional impairment at hospital discharge, and a lower proportion of patients had aphasia symptoms, and premorbid history of dementia, compared to those unable to participate. NIHTB-CB tests were obtainable in only 9 (12% overall) patients, and non-participation was deemed not due to the reduced level of consciousness as the majority completed PROMIS assessments and did not differ from untestable patients by level of self-reported cognitive symptoms. Authors concluded that there is a severe discordance in patient-reported and objective cognitive assessments among patients in the early recovery phase, suggesting infeasibility, invalidity, and unsuitable nature of cognitive tests that were validated for use in patients with chronic medical and neurologic illnesses.

As highlighted by the authors, the study had few limitations including small sample size, which was performed in a single center, and the data from two heterogeneous populations were combined, thus reducing the internal validity of the findings; compared to patients admitted with sepsis, ICH patients had worse participation rates.

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