Association between aspirin therapy and the outcome in critically ill patients: a nested cohort study

Background: Antiplatelet therapy may attenuate the undesirable effects of platelets on the inflammatory cascades in critical illness. The objective of this study was to evaluate the association between aspirin therapy during intensive care unit (ICU) stay and all-cause mortality. Methods: This was a nested cohort study within two randomized controlled trials in which all enrolled patients (N = 763) were grouped according to aspirin intake during ICU stay. The primary endpoints were all-cause ICU mortality and hospital mortality. Secondary endpoints included the development of severe sepsis during the ICU stay, ICU and hospital length of stay and the duration of mechanical ventilation. Propensity score was used to adjust for clinically and statistically relevant variables. Results: Of the 763 patients, 154 patients (20 %) received aspirin. Aspirin therapy was not associated with a reduction in ICU mortality (adjusted OR 1.18, 95 % CI 0.69-2.02, P = 0.55) nor with hospital mortality (adjusted OR 0.95, 95 % CI 0.61-1.50, P = 0.82). Aspirin use had no preferential association with mortality among any of the study subgroups. Additionally, aspirin therapy was associated with higher risk of ICU-acquired severe sepsis, and increased mechanical ventilation duration and ICU length of stay. Conclusion: Our study showed that the use of aspirin in critically ill patients was not associated with lower mortality, but rather with an increased morbidity.