Aggressive tactics by one of the nation's largest collectors of medical debts, Accretive Health, were revealed on Tuesday by the Minnesota attorney general, raising concerns that such practices have become common at hospitals across the country. The tactics, like embedding debt collectors as employees in emergency rooms and demanding that patients pay before receiving treatment, were outlined in hundreds of company documents released by the attorney general. And they cast a spotlight on the increasingly desperate strategies among hospitals to recoup payments as their unpaid debts mount.