BACKGROUND: Survey data suggest that Canadian intensivists administer corticosteroids to critically ill patients primarily in response to airway obstruction, perceived risk for adrenal insufficiency and hemodynamic instability.OBJECTIVE: To describe variables independently associated with systemic corticosteroid therapy during an influenza outbreak.METHODS: The present analysis was retrospective cohort study involving critically ill patients with influenza in two Canadian cities. Hospital records were reviewed for critically ill patients treated in the intensive care units (ICUs) of eight hospitals in Canada during the 2008 to 2009 and 2009 to 2010 influenza outbreaks. Abstracted data included demographic information, symptoms at disease onset, chronic comorbidities and baseline illness severity scores. Corticosteroid use data were extracted for every ICU day and expressed as hydrocortisone dose equivalent in mg. Multivariable regression models were constructed to identify variables independently associated with corticosteroid therapy in the ICU.RESULTS: The study cohort included 90 patients with a mean (± SD) age of 55.0±17.3 years and Acute Physiology and Chronic Health Evaluation II score of 19.8±8.3. Patients in 2009 to 2010 were younger with more severe lung injury but similar exposure to corticosteroids. Overall, 54% of patients received corticosteroids at a mean daily dose of 343±330 mg of hydrocortisone for 8.5±4.8 days. Variables independently associated with corticosteroid therapy in the ICU were history of airway obstruction (OR 4.8 [95% CI 1.6 to 14.9]) and hemodynamic instability (OR 4.6 [95% CI 1.2 to 17.8]).CONCLUSION: Observational data revealed that hemodynamic instability and airway obstruction were associated with corticosteroid therapy in the critical care setting, similar to a recent survey of stated practice. Efforts to determine the effects of corticosteroids in the ICU for these specific clinical situations are warranted.