Computer simulation of patient flow through an operating suite

Operating room (OR) inefficiency is costly and stressful for patients and staff. To evaluate possible improvements, we simulated our OR and Recovery Room (RR) processes with Stata. We used hospital data (in long format) and parametric time-to-event regression (streg) to derive log-logistic distributions for the duration of procedures, RR stays, and room turnaround. Variables were then reshaped into a single row (wide format) for the simulation program. Patient and room status for a 24-hour day were changed sequentially using a forvalues loop with 5-minute steps. Scheduled and historical times were first used deterministically to recreate anticipated and actual events and durations. Patient observations were then replicated (using expand) with different pseudo-random parameters in each row. Distributions of patient length of stay in OR and RR (and room turnaround times) thus approximated theoretical input distributions. Refinements included reassigning cases if the scheduled room was running late, changing staff availability, and incorporating unscheduled emergencies. Summary statistics were compiled (using egen) for each case and the system as a whole, and were consistent with historical data. Stata has some advantages over specialized simulation programs, especially for current Stata users. We plan build a user interface, make other improvements, and share our program through RePEc.