[Planning for the Possible in Healthcare: From PEIMAF to the Management of the Unknown.].

This paper examines the evolution of healthcare planning in light of the increasing complexity of contemporary emergencies, which are characterized by high levels of uncertainty and the frequent absence of established interpretative models. Starting from the historical role of Hospital Emergency Plans for Mass Casualty Incidents (PEIMAF), the article highlights the limitations of approaches based solely on known scenarios and proposes a conceptual shift toward managing the unknown. It outlines the need to broaden the operational meaning of PEIMAF, extending it to all types of patients and transforming the concept of a "plan" into a dynamic process of developing decision-making capacity. Within this framework, a model structured on two integrated levels is proposed: an operational level, grounded in continuous training and practical exercises, and a decision-making level, focused on adaptability, experimentation, and the development of new solutions in uncertain contexts. Particular attention is given to strengthening decision-making skills through training pathways based on complex, multidisciplinary, and highly variable simulations, aimed at fostering proactive and adaptive capabilities. The paper ultimately emphasizes that the resilience of healthcare systems lies in the quality of decisions made under uncertainty, highlighting the need for a cultural and organizational evolution that integrates planning, training, and decision-making capacity to ensure effective responses to future crises.