1. UCSD Health Department of Biomedical Informatics, University of California San Diego, La Jolla, California, USA
2. Department of Anesthesiology, University of California San Diego, San Diego, California, USA
3. Department of Orthopaedic Surgery, University of California at San Diego, San Diego, California, USA
4. Division of Health Services Research & Development, VA San Diego Healthcare System, San Diego, California, USA