The Felix Bulnes Hospital serves a population of 497,177 inhabitants from El Bosque and San Bernardo districts in Santiago, Chile. One of the priorities for this public Hospital is the optimization of its emergency room service. This service received more than 40,000 patients last year. One of the key factors was the overload due to environmental/winter and/or emergency related conditions that affected the population which resulted in an unusual pattern flow and normal process disruption. We propose a simulation-based optimization model for dealing with such overload capacity enabling us to identify demand according to complexity, analyze productivity and performance, and waiting and execution time process improvement, among others.