Long-term Cognitive Impairment and Delirium in Intensive Care: A Prospective Cohort Study

Background: Whilst there is a growing body of research exploring the effect of delirium in intensive care unit (ICU) patients, the relationship between patient delirium and long-term cognitive impairment has not been investigated in settings where low rates of delirium have been reported.

Objectives: To assess the association between the incidence of delirium, duration of mechanical ventilation and long term cognitive impairment in general ICU patients.

Methods: Prospective cohort study conducted in a tertiary level ICU in Queensland, Australia. Adult medical and surgical ICU patients receiving ≥12h mechanical ventilation were assessed for delirium on at least one day. Cognitive impairment was assessed at three and/or six-months using the: Repeatable Battery for the Assessment of Neuropsychological Status (RBANS); Trail Making Test (TMT) Part A and B; and Mini-Mental State Examination (MMSE).

Results: Of 148 enrollees, 91 (61%) completed assessment at three and/or six months. Incidence of delirium was 19%, with 41% cognitively impaired at three months and 24% remaining impaired at six months. Delirium was associated with impaired cognition at six-months: mean TMT Part A scores (information processing speed) were 7.86s longer than those with no delirium (p=0.03), and mean TMT Part B scores (executive functioning) 24.0s longer (p=0.04).

Conclusions: ICU delirium was positively associated with impaired information processing speed and executive functioning at six-months post-discharge for this cohort. Testing for cognitive impairment with RBANS and TMT should be considered due to its greater sensitivity in comparison to the MMSE.