TREATMENTS, RESOURCE UTILIZATION, AND OUTCOMES OF COVID-19 PATIENTS PRESENTING TO EMERGENCY DEPARTMENTS ACROSS PANDEMIC WAVES: AN OBSERVATIONAL STUDY BY THE CANADIAN COVID-19 EMERGENCY DEPARTMENT RAPID RESPONSE NETWORK (CCEDRRN)

Hohl, C. M.; Rosychuk, R. J.; Hau, J. P.; Hayward, J.; Landes, M.; Yan, J. W.; Ting, D. K.; Welsford, M.; Archambault, P. M.; Mercier, E.; Chandra, K.; Davis, P.; Vaillancourt, S.; Leeies, M.; Small, S.; Morrison, L. J.; Network, Canadian COVID-19 Emergency Department Rapid Response

Background: Treatment strategies for coronavirus disease 2019 (COVID-19) evolved between pandemic waves. Our objective was to compare treatments, acute care resource utilization, and outcomes of COVID-19 patients presenting to Emergency Departments across two pandemic waves. Methods: This observational study enrolled consecutive eligible COVID-19 patients presenting to 46 Emergency Departments participating in the Canadian COVID-19 Emergency Department 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. We used logistic regression modeling to assess the impact of pandemic wave on outcomes. Results: We 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 Emergency Department. Adjusted for patient characteristics and disease severity, steroid use increased (odds ratio [OR] 8.0; 95% confidence interval [CI] 6.4 -- 10.0), while the use of invasive mechanical ventilation decreased (OR 0.5; 95%CI 0.4 -- 0.6) in the second wave. 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 0.6; 95%CI 0.4 -- 0.7) decreased, while mortality remained unchanged (OR 1.0; 95%CI 0.7-1.4). Interpretation: In patients presenting to Canadian acute care facilities, rapid uptake of steroid therapy was evident. Mortality was stable despite lower critical care utilization in the second wave.