###### Abstract
[39] proposed a simulation and mixed integer programming model to integrate and improve surgical scheduling and predict ward and leveling bed occupancy, respectively. [PERSON] et al. [13] investigated a medium-level planning problem to calculate the demand distribution of downstream departments for a given master surgery schedule. They developed a method to optimize the master surgery schedule and analyzed the impact of resulting block allocation on the bed requirements in the ICU and general wards. [PERSON] [18] integrated the strategic and tactical master surgery scheduling while considering the impact on downstream resources such as the ICU and general patient wards. The study aimed to increase hospital earnings by optimizing the master surgery schedule. [PERSON] et al. [9] studied the case mix planning problem with consideration of the resources of downstream wards. They developed mathematical models to generate a pool of solutions with different case mix plans and employed a simulation to evaluate each solution for the overutilization of the operating theatre and variability in bed usage in downstream wards. In their multi-phase solution approach, they developed four mixed integer programming models for case mix planning, block allocation, and master surgery scheduling, and used simulations to assess the quality of the generated solution. In another article, [PERSON] and [PERSON] [11] developed a master surgery schedule and proposed a stochastic programming model to integrate the medium-level decision-making of operating rooms with downstream departments such as intensive care units and wards. In their approach, they estimated the bed requirements at the operational level and developed master surgery schedules based on these estimates of bed requirements. In most of the literature, the planning and scheduling problems did not consider the interconnection of the critical resources with the other interlinked wards. For a feasible and realistic solution to the health care system, the interconnection of the operating room with the ICU and ward cannot be ignored, and the optimization of the operating theatre alone may result in the underutilization or congestion of other resources and may lead to infeasible schedules. Hence, it is proposed in the present study that the optimal utilization of operating rooms integrated with the ICU and ward can lead to feasible and optimal solutions and enhance the performance of the healthcare facility as a whole because the operating rooms also pace the activities of the linked units. Optimizing the utilization of the operating room alone without considering the capacity constraints of downstream units may result, in some cases, in the underutilization of these units and, in other cases, congestion in these downstream units, which ultimately leads to early discharge or even surgery cancellations. For the balanced use of all the hospital resources, it is necessary to consider the planning and scheduling of operating rooms in combination with interconnected downstream wards. This work, therefore, aims to integrate higher-level, medium-level, and operational-level planning and scheduling along with the integration of the planning and scheduling of operating rooms with downstream units such as beds in the ICU and ward. Such a problem of the simultaneous consideration of all decision levels and critical resources of the healthcare system is new and, to the best of the authors' knowledge, has not been addressed so far in the literature. In the literature, the theory of constraints was used to improve the overall system performance while focusing on only the critical resource [40; 41]. The theory of constraints applies the drum buffer rope method to identify the resource with limiting capacity, called the drum, and a rope mechanism to provide the planning information to upstream resourcesof the drum for effective planning and execution. To fully utilize the drum resource, buffers in the form of time and material are provided to prevent the drum from starvation.