Simulation has been used for modeling in healthcare for many decades. Ranging from the modeling of physiological processes to group dynamics to the modeling of strategic and system-wide models of healthcare provision, simulation promises to be an effective approach to analyze healthcare operations. Effective application of simulations in healthcare operations requires that simulation deal with wide variability and unpredictability in workflow processes, the complexity of healthcare organizations and enables the participation of human experts in the modeling and operations processes. In this paper, based on requirements drawn from a participatory simulation with healthcare practitioners, we define a hybrid, composable approach to healthcare simulations. Both the participatory simulation and the composable simulation are applied in the context of the New Karolinska Solna hospital in Sweden, a highly specialized new hospital. Results point to the need to accounting for variability in workflow processes and integration with existing IT infrastructure in hospitals.