Frequency and Trends of Pre-Pandemic Surge Periods in U.S. Emergency Departments, 2006–2019

OBJECTIVES: To quantify the frequency, outside of the pandemic setting, with which individual healthcare facilities faced surge periods due to severe increases in demand for emergency department (ED) care. DESIGN: Retrospective cohort study. SETTING: U.S. EDs. PATIENTS: All ED encounters in the all-payer, nationally representative Nationwide Emergency Department Sample from the Healthcare Cost and Utilization Project, 2006–2019. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Frequency of surge periods defined as ED months in which an individual facility ED saw a greater than 50% increase in ED visits per month above facility-/calendar month-specific medians. During 2006–2019, 3,317 U.S. EDs reported 354,534,229 ED visits across 142,035 ED months. Fifty-seven thousand four hundred ninety-five ED months (40.5%) during the study period had a 0% to 50% increase in ED visits that month above facility-specific medians and 1,952 ED months (1.4%) qualified as surge periods and had a greater than 50% increase in ED visits that month above facility-specific medians. These surge months were experienced by 397 unique facility EDs (12.0%). Compared with 2006, the most proximal pre-pandemic period of 2016–2019 had a notably elevated likelihood of ED-month surge periods (odds ratios [ORs], 2.36–2.84; all p < 0.0005). Compared with the calendar month of January, the winter ED months in December through March have similar likelihood of an ED-month qualifying as a surge period (ORs, 0.84–1.03; all p > 0.05), while the nonwinter ED months in April through November have a lower likelihood of an ED-month qualifying as a surge period (ORs, 0.65–0.81; all p < 0.05). CONCLUSIONS: Understanding the frequency of surges in demand for ED care—which appear to have increased in frequency even before the COVID-19 pandemic and are concentrated in winter months—is necessary to better understand the burden of potential and realized acute surge events and to inform cost-effectiveness preparedness strategies.