Epidemiology of Delirium in the Intensive Care Unit

Abstract

Delirium is a common neuropsychiatric syndrome in critically ill patients, characterized by a disturbance in attention and cognition. Delirium is not an inevitable consequence of critical illness itself, however, it is associated with poor patient outcomes such as an increased ICU length of stay and cognitive impairment one year after ICU discharge. It is believed that delirium is caused by an interplay between predisposing factors that make a patient more susceptible to develop delirium (for example higher age), and noxious insults that can provoke delirium (such as infection, medication or trauma). As delirium imposes a significant burden on patients, their relatives, health care professionals and health care systems, the factors that can be modified for possible prevention of delirium are of special interest. In this thesis some of these modifiable risk factors are determined.

In 1112 critically ill patients admitted to the ICU of the University medical Center Utrecht (UMCU) delirium was common with an incidence of 48%. In 43% of the delirious patients delirium occurred only once during their ICU admission for a period of one day. In this thesis it was shown that a higher anticholinergic drug exposure at ICU admission affected the onset of delirium during ICU stay with a subdistribution hazard ratio of 1.35 (95% Confidence Interval [CI]: 1.09-1.68). Benzodiazepines are frequently used in critically ill patients for patient comfort and safety. The administration of as little as 5 mg benzodiazepines (in midazolam equivalents) in non-comatose, non-delirious patient was associated with the development of delirium the next day (odds ratio 1.04, 95% CI: 1.03-1.05). In a before-after study the onset and duration of delirium in a ward-like ICU environment was compared toa newly build ICU with all single-rooms and, among other interventions, an increased exposure to natural daylight. Although patients had a similar risk of developing delirium in the single-room ICU, the number of days that patients suffered from a delirium decreased with 0.4 (955 CI: 0.1-0.7) days. Earlier findings show an increased ICU mortality with the development of delirium while adjusting for the disease severity at ICU admission. In this thesis we additionally adjusted for the evolution of disease severity after ICU admission and for competing events of developing delirium (i.e. ICU discharge and death as they both preclude the development of delirium during ICU admission). Doing so, delirium did not attribute to death during ICU admission. However, patients with delirium were less likely to be discharged, exposing them, on average, for longer period of time to the ICU with an everyday risk of dying. When specifying prolonged delirium (two or more days) this prolonged delirium did have an association with increased ICU mortality.