Long-term Cognitive and Functional Impairments After Critical Illness

Abstract

As critical illness survivorship increases, patients and health care providers are faced with management of long-term sequelae including cognitive and functional impairment. Longitudinal studies have demonstrated impairments persisting at least 1–5 years after hospitalization for critical illness. Cognitive domains impacted include memory, attention, and processing speed. Functional impairments include physical weakness, reduced endurance, and dependence on others for basic tasks of daily living such as bathing or feeding. In characterizing the trajectory of long-term recovery, multiple risk factors have been identified for subsequent impairment, including increased severity of illness and severe sepsis, prolonged mechanical ventilation, and delirium. Preadmission status including frailty, high level of preexisting comorbidities, and baseline cognitive dysfunction are also associated with impairment after critical illness. Development of cognitive and functional impairment is likely multifactorial, and multiple mechanistic theories have been proposed. Neuroinflammation, disruption of the blood–brain barrier, and structural alterations in the brain have all been observed in patients with long-term cognitive dysfunction. Systemic inflammation has also been associated with alterations in muscle integrity and function, which is associated with intensive care unit–acquired weakness and prolonged functional impairment. Efforts to ease the burden of long-term impairments include prevention strategies and rehabilitation interventions after discharge. Delirium is a well-established risk factor for long-term cognitive dysfunction, and using delirium-prevention strategies may be important for cognitive protection. Current evidence favors minimizing overall sedation exposure, careful selection of sedation agents including avoidance of benzodiazepines, and targeted sedation goals to avoid oversedation. Daily awakening and spontaneous breathing trials and early mobilization have shown benefit in both cognitive and functional outcomes. Multifactorial prevention bundles are useful tools in improving care provided to patients in the intensive care unit. Data regarding cognitive rehabilitation are limited, while studies on functional rehabilitation have conflicting results. Continued investigation and implementation of prevention strategies and rehabilitation interventions will hopefully improve the quality of life for the ever-increasing population of critical illness survivors.