1. Anesthesiology and Perioperative Care Service, Veterans Affairs Palo Alto Health Care System; Palo Alto, California, USA
2. Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University School of Medicine; Stanford, California, USA
3. Department of Anesthesiology, Division of Regional Anesthesia, University of California, San Diego; California, USA
4. Department of Medicine, Division of Biomedical Informatics, University of California, San Diego; California, USA