Time trends of delirium rates in the intensive care unit.

Background: Effects of clinical practice changes on ICU delirium are not well understood.

Objectives: Determine ICU delirium rates over time.

Methods: Data from a previously described screening cohort of the Pharmacological Management of Delirium trial was analyzed. Richmond Agitation-Sedation Scale (RASS) and Confusion Assessment Method for the ICU (CAM-ICU) were assessed twice daily. We defined: Any delirium (positive CAM-ICU at any time during ICU stay) and ICU-acquired delirium (1st CAM-ICU negative with a subsequent positive CAM-ICU). Mixed-effects logistic regression models were used to test for differences.

Results: 2742 patient admissions were included. Delirium occurred in 16.5%, any delirium decreased [22.7% to 10.2% (p < 0.01)], and ICU-acquired delirium decreased [8.4% to 4.4% (p = 0.01)]. Coma decreased from 24% to 17.4% (p = 0.04). Later ICU years and higher mean RASS scores were associated with lower odds of delirium.

Conclusions: Delirium rates were not explained by the measured variables and further prospective research is needed.