Dynamics of bed use in accommodating emergency admissions: stochastic simulation model

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Abstract
Objective: To examine the daily bed requirements arising from the flow of emergency admissions to an acute hospital, to identify the implications of fluctuating and unpredictable demands for emergency admission for the management of hospital bed capacity, and to quantify the daily risk of insufficient capacity for patients requiring immediate admission. Design: Modelling of the dynamics of the hospital system, using a discrete-event stochastic simulation model, which reflects the relation between demand and available bed capacity. Setting: Hypothetical acute hospital in England. Subjects: Simulated emergency admissions of all types except mental disorder. Main outcome measures: The risk of having no bed available for any patient requiring immediate admission; the daily risk that there is no bed available for at least one patient requiring immediate admission; the mean bed occupancy rate. Results: Risks are discernible when average bed occupancy rates exceed about 85%, and an acute hospital can expect regular bed shortages and periodic bed crises if average bed occupancy rises to 90% or more. Conclusions: There are limits to the occupancy rates that can be achieved safely without considerable risk to patients and to the efficient delivery of emergency care. Spare bed capacity is therefore essential for the effective management of emergency admissions, and its cost should be borne by purchasers as an essential element of an acute hospital service. Acute hospitals which operate at bed occupancy levels of 90% or more face regular bed crises, with the associated risks to patients Management interventions should focus on measures with long term benefits to counteract the growth trend in demand for admission Many initiatives have only a short term effect; they briefly delay the worst effects but do not address the growing mismatch between supply and demand Evaluating management interventions year on year at a single hospital is futile—any effects are swamped by random variations