The chief medical officer during Parkland Memorial Hospital's years-long safety crisis is now overseeing one of the nation's most famous health institutions. Dr. John Jay Shannon was promoted Friday to interim chief executive at Chicago's Cook County Health & Hospitals System. That puts him over John H. Stroger Jr. Hospital, inspiration for the television show ER. Shannon has been there less than a year as a high-level clinical administrator. He temporarily replaces the man who hired him. Dr. Ramanathan Raju, who is taking a job in New York, said last year that Shannon's role in Dallas hadn't troubled him.