Big Nashville-based hospital chains should brace for stepped-up efforts to recruit their nurses if a series of mergers and agreements among some of the nation's largest healthcare workers' unions achieves organizers' goals. Nurse organizers expect that a larger organization with 150,000 members and the arrangement with the Service Employees International Union will provide a boost to organizing efforts at chains such as HCA. Recruiting nurses has been difficult in Southern states, including Tennessee, where laws don't allow for mandatory union membership at work.