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Delirium in critically ill patients is associated with higher mortality. Preventing and treating delirium through less use of benzodiazepines, earlier mobilization, and restoration of day-night sleep cycles has become common. However, it is unclear whether delirium is an independent cause — rather than just a marker — of higher mortality for patients in the intensive care unit (ICU). To examine this question, investigators prospectively studied 1112 patients who were admitted to a 32-bed medical-surgical ICU in the Netherlands. Delirium was documented on 26% of ICU days (median duration of delirium, 3 days).
Patients who developed delirium, compared with those who did not, were older, more likely to abuse alcohol, and more critically ill, with higher rates of sepsis and mechanical ventilation at admission. Crude mortality during ICU stays was higher for delirium patients (17% vs. 7%), but this difference disappeared after adjustment for evolution of disease severity before delirium onset.
In post-hoc analyses, prolonged duration of delirium was associated with a small increase in ICU mortality, but this effect was mediated by prolonged ICU stay — and not by increase in daily mortality.
Klein Klouwenberg PM et al. The attributable mortality of delirium in critically ill patients: Prospective cohort study. BMJ 2014 Nov 24; 349:g6652. (http://dx.doi.org/10.1136/bmj.g6652)
Comment
Delirium is a marker of degree of critical illness: Sicker patients are more likely to develop delirium and to die, but delirium itself does not appear to drive this mortality. Delirium is unpleasant for patients, and efforts to prevent it are warranted, but we're unlikely to change mortality in the ICU dramatically with these interventions.