1. From the Department of Anesthesiology and Pain Medicine, University of Washington, Seattle, Washington
2. Department of Anesthesiology and Perioperative Medicine, University of California, Los Angeles, Los Angeles, California
3. Department of Orthopaedic Surgery, Keck School of Medicine of the University of Southern California, Los Angeles, California
4. Department of Anesthesiology, Keck School of Medicine of the University of Southern California, Los Angeles, California.