The association between acute respiratory distress syndrome, delirium, and in-hospital mortality in intensive care unit patients

Rationale: Both acute respiratory distress syndrome (ARDS) and intensive care unit (ICU) delirium are associated with significant morbidity and mortality. However, the risk of delirium and its impact on mortality in ARDS patients is unknown. Objectives: To determine if ARDS is associated with a higher risk for delirium compared with respiratory failure without ARDS, and to determine the association between ARDS and in-hospital mortality after adjusting for delirium. Methods: Prospective observational cohort study of adult ICU patients admitted to two urban academic hospitals. Measurements and Main Results: Delirium was assessed daily using the Confusion Assessment Method for the ICU and Richmond Agitation and Sedation Scale. Of the 564 patients in our cohort, 48 had ARDS (9%). Intubated patients with ARDS had the highest prevalence of delirium compared with intubated patients without ARDS and nonintubated patients (73% vs. 52% vs. 21%, respectively; P < 0.001). After adjusting for common risk factors for delirium, ARDS was associated with a higher risk for delirium compared with mechanical ventilation without ARDS (odds ratio [OR], 6.55 [1.56-27.54]; P = 0.01 vs. OR, 1.98 [1.16-3.40]; P < 0.013); reference was nonintubated patients. Although ARDS was significantly associated with hospital mortality (OR, 10.44 [3.16-34.50]), the effect was largely reduced after adjusting for delirium and persistent coma (OR, 5.63 [1.55-20.45]). Conclusions: Our findings suggest that ARDS is associated with a greater risk for ICU delirium than mechanical ventilation alone, and that the association between ARDS and in-hospital mortality is weakened after adjusting for delirium and coma. Future studies are needed to determine if prevention and reduction of delirium in ARDS patients can improve outcomes.