Steven Sonenreich's second tenure at Mount Sinai Medical Center has been more tumultuous than his first. When he started working at Mount Sinai in 1976 in the billing office, he was a young college graduate. He quickly rose through the ranks to chief operating officer, served as COO from 1989 until 1996, then became chief executive officer of the old Cedars Medical Center in Miami, now known as University of Miami Hospital. When Sonenreich came back to Mount Sinai five years later as its chief executive officer, the waterfront hospital overlooking Biscayne Bay was nearly insolvent. Today its financial prognosis is far healthier. Management soon expects to report its fourth annual profit in a row.