• Corinne M Hohl, Rhonda J Rosychuk, Jeffrey P Hau, Jake Hayward, Megan Landes, Justin W Yan, Daniel K Ting, Michelle Welsford, Patrick M Archambault, Eric Mercier, Kavish Chandra, Philip Davis, Samuel Vaillancourt, Murdoch Leeies, Serena Small, Laurie J Morrison, and Canadian COVID-19 Rapid Response Network (CCEDRRN) investigators for the Network of Canadian Emergency Researchers, for the Canadian Critical Care Trials Group.
• Department of Emergency Medicine, University of British Columbia, Vancouver, BC, Canada. corinne.hohl@ubc.ca.
• CJEM. 2022 Jun 1; 24 (4): 397407397-407.

BackgroundTreatment for coronavirus disease 2019 (COVID-19) evolved between pandemic waves. Our objective was to compare treatments, acute care utilization, and outcomes of COVID-19 patients presenting to emergency departments (ED) across pandemic waves.MethodsThis observational study enrolled consecutive eligible COVID-19 patients presenting to 46 EDs participating in the Canadian COVID-19 ED Rapid Response Network (CCEDRRN) between March 1 and December 31, 2020. We collected data by retrospective chart review. Our primary outcome was in-hospital mortality. Secondary outcomes included treatments, hospital and ICU admissions, ED revisits and readmissions. Logistic regression modeling assessed the impact of pandemic wave on outcomes.ResultsWe enrolled 9,967 patients in 8 provinces, 3,336 from the first and 6,631 from the second wave. Patients in the second wave were younger, fewer met criteria for severe COVID-19, and more were discharged from the ED. Adjusted for patient characteristics and disease severity, steroid use increased (odds ratio [OR] 7.4; 95% confidence interval [CI] 6.2-8.9), and invasive mechanical ventilation decreased (OR 0.5; 95% CI 0.4-0.7) in the second wave compared to the first. After adjusting for differences in patient characteristics and disease severity, the odds of hospitalization (OR 0.7; 95% CI 0.6-0.8) and critical care admission (OR 0.7; 95% CI 0.6-0.9) decreased, while mortality remained unchanged (OR 0.7; 95% CI 0.5-1.1).InterpretationIn patients presenting to cute care facilities, we observed rapid uptake of evidence-based therapies and less use of experimental therapies in the second wave. We observed increased rates of ED discharges and lower hospital and critical care resource use over time. Substantial reductions in mechanical ventilation were not associated with increasing mortality. Advances in treatment strategies created health system efficiencies without compromising patient outcomes.Trial RegistrationClinicaltrials.gov, NCT04702945.© 2022. The Author(s).

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