1 Department of Anesthesiology, Pain Research Center, University of Utah School of Medicine, Suite 200, 615 Arapeen Drive, Salt Lake City, UT 84109, USA. Electronic address: perry.fine@hsc.utah.edu.
2 Department of Anesthesiology and Critical Care, Penn Pain Medicine Center, University of Pennsylvania, 1840 South Street, Philadelphia, PA 19146, USA. Electronic address: michael.ashburn@uphs.upenn.edu.