Cognitive impairments after critical illness

Cognitive impairments are common after critical illness. Aetiology and effects of cognitive impairments in this setting are not fully revealed. The aim of this study was to investigate the effect of critical illness and intensive care unit (ICU) treatment on cerebral function.

Adult ICU patients with no previous history of cerebral disorders were included. Non-delirious patients scoring ≥  24 on mini-mental state examination on ICU discharge were explored neuropsychologically using the Cambridge Neuropsychological Test Automated Battery (CANTAB) to classify cognitive impairments. Tests were repeated at 3 and 12 months. Results were compared with a normal reference population and a surgical comparison group.

We included 55 patients. Eighteen of 28 patients were cognitively impaired, and it was not possible to classify 27 patients. The ICU survivors tested with CANTAB scored significantly lower than the reference population. They also scored worse than a surgical comparison group but significantly on only one of 10 measures. At 3 months follow-up, included patients scored significantly worse on one of 10 reported CANTAB measures. There were no differences at 12 months. We found no associations between age, co-morbidity, Simplified Acute Physiology Score II, Sequential Organ Failure Assessment score, presence of cardiovascular disease, duration of ventilatory support and length of ICU stay, and cognitive impairments. Having a cognitive impairment did not affect other outcome measures such as mortality, health-related quality of life, and institutionalization.

Cognitive impairments are common after critical illness and may be caused by the critical illness in itself. Incidences are high after ICU discharge (64%) but drops rapidly during the first 3 months after discharge.