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)

ABSTRACT 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. Trial Registration Clinicaltrials.gov, NCT04702945