Using mixed integer programming and constraint programming for operating rooms scheduling with modified block strategy

Operating Room (OR) Scheduling is one of the most critical problems at the operational level for hospital managers. A useful strategy for OR scheduling, especially in large hospitals is the block strategy. In this strategy, a specific time is blocked for each surgeon or surgical team. This strategy usually leads to unused operating rooms’ capacity. To overcome this problem, in this article, a novel modified block strategy is presented for the daily scheduling of elective patients. This study aims to find the optimal sequence and schedule of patients by minimizing the cost of overtime, makespan and completion time of surgeons’ operations by considering the resource constraints. Considering the limitations and real conditions of Al-Zahra Hospital, the largest educational hospital in Isfahan, Iran, is also an aspect of this study. The problem is modeled by mixed integer programming and Constraint Programming (CP). The performance of the models is verified by several random test instances. The results indicate that CP is more efficient than mathematical modeling in terms of the computational time for solving the considered problems, especially for large-size instances. The average percent of improvement in computational time is about 53% using the CP model. The proposed CP model is also used to solve real problem instances from Al-Zahra hospital. The results show that by using the CP model, the completion time of surgeons’ operations is shortened by 9% and ORs’ overtime and makespan objectives are reduced by 55% and 20% respectively.