Models for Determining Estimated Start Times and Case Orderings In Hospital Operating Rooms-

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Abstract
In this paper, we address a number of scheduling problems that are often faced in a hospital's operating room (OR). The operating room can be modeled as a one machine job shop where the surgical procedures are thought of as the jobs and the operating room itself is the machine. The procedure (job) times are stochastic and the operating room scheduler exerts control over the schedule of jobs. The situation can also be thought of as a D/GI/1 queueing system, where the arrival times of the customers are a decision variable. Initially we address the problem where the scheduler is given the sequence of jobs and must determine the estimated starting times of the procedures in order that the surgeons may plan their personal schedules with respect to hospital rounds and office visits. The costs that must be balanced are (1) the idle time costs if the estimated starting time is later than the actual available start time, and (2) the surgeon's waiting time if the estimated starting time is before the actual ending time of the previous case. We also address the problem of jointly determining both the optimal order and the assigned starting times of a given group of procedures. The estimated starting times of the procedures are found to depend upon a single critical number that is easily determined from the relevant costs of the problem. Both analytic and simulation results are presented. The results of this paper can be used directly in hospital operating rooms as well as any system where a decision maker can exert control over the arrivals.