Impact of a Full-Scale Mass Casualty Exercise on Emergency Department Operations at a Level One Trauma Center and Tertiary Referral Hospital

Introduction: Emergency departments (EDs) must be prepared for sudden surges of critically ill patients. To maintain readiness, United States (U.S.) hospitals conduct full-scale mass casualty (MCI) exercises, though few studies examine their impact on real-time patient care in active EDs. This study addresses this gap by evaluating the operational impacts of a full-scale exercise (FSE) conducted at a major U.S. level one trauma and tertiary referral center. On a Wednesday morning, 78 moulaged patients tested the ED’s surge capacity with a layered staffing model simulating disaster response demand. This study aims to determine if high-fidelity FSEs can integrate into active EDs without affecting real patient care. Methods: Data from the electronic medical record was collected over two time periods on the exercise day and control days: the exercise (6 hours) and impacted clinician’s shift (14 hours). The primary outcome was the median length of stay (LOS) for real patients. Secondary outcomes included door-to-doctor time, time to disposition, and arrival-to room time. Medians from the exercise day were compared to control dates (four preceding and four following Wednesdays) using the Mann-Whitney U test. Results: Median LOS during the exercise was 164 minutes, while control days during the same time were 162 minutes. Median LOS for the impacted clinician shift during the exercise was 190 minutes, while control days were 174 minutes. For the exercise period, no statistically significant differences were found for LOS and all secondary outcomes. For the impacted clinician shift, only LOS demonstrated a statistically significant difference (p=0.043). Conclusion: With strategic planning, FSEs can be integrated into active EDs with minimal impact on patient care and operations. FSE planning should aim to minimize disruptions and include objective tracking metrics to evaluate the success of these efforts. Future studies should assess patient outcomes, return visits, and clinician cognitive load for a more comprehensive evaluation of FSE impacts.