A simulation model of patient flow through the emergency department to determine the impact of a short stay unit on hospital congestion

One of the most critical and costly decisions made in emergency departments (EDs) is whether to admit a patient into the hospital. These decisions require investment in time for patient testing and treatment, delaying care to other patients. Short-stay units (SSUs) are an alternative to discharging or fully admitting ED patients, allowing extended patient observation. However, little is understood about the design of an SSU and its impact on outcomes and congestion. Here, we introduce a discrete-event simulation model of a hospital system (ED, inpatient units, and SSUs). By analyzing records from a tertiary teaching hospital, we determine realistic parameters and identify important features, such as triage level and processes depending on triage level, time, and congestion. We contend that performance metrics, e.g. time to first contact, critically depend on downstream hospital units. To demonstrate utility, we use the simulation model to assess bed occupancy over time.