Hospital chain HCA Holdings Inc. has posted healthy profits at its three hospitals in Southern California. In Southern California, HCA runs Riverside Community Hospital, Los Robles Regional Medical Center in Thousand Oaks and West Hills Hospital and Medical Center. All three hospitals have generated strong profits for HCA in recent years, according to state records. Riverside Community, the largest of the three with 373 beds, had an operating profit margin of 13% last year on total operating revenue of $410 million. The average operating margin for California hospitals was 3.4% at the end of last year, according to the Office of Statewide Health Planning and Development.