Cognitive impairment after intensive care unit admission: a systematic review

There is increasing evidence that critical illness and treatment in an intensive care unit (ICU) may result in significant long-term morbidity. The purpose of this systematic review was to summarize the current literature on long-term cognitive impairment in ICU survivors.

PubMed/MEDLINE, CINAHL, Cochrane Library, PsycINFO and Embase were searched from January 1980 until July 2012 for relevant articles evaluating cognitive functioning after ICU admission. Publications with an adult population and a follow-up duration of at least 2 months were eligible for inclusion in the review. Studies in cardiac surgery patients or subjects with brain injury or cardiac arrest prior to ICU admission were excluded. The main outcome measure was cognitive functioning.

The search strategy identified 1,128 unique studies, of which 19 met the selection criteria and were included. Only one article compared neuropsychological test performance before and after ICU admission. The 19 studies that were selected reported a wide range of cognitive impairment in 4-62 % of the patients after a follow-up of 2-156 months.

The results of most studies of the studies reviewed suggest that critical illness and ICU treatment are associated with long-term cognitive impairment. Due to the complexity of defining cognitive impairment, it is difficult to standardize definitions and to reach consensus on how to categorize neurocognitive dysfunction. Therefore, the magnitude of the problem is uncertain.