1. Department of Anesthesiology, Mayo Clinic, 13400 East Shea Boulevard, Scottsdale, AZ 85259-5404, USA
2. Department of Anesthesiology, Jefferson Medical College, Thomas Jefferson University, 111 South 11th Street, PA 19107, USA
3. Naples Anesthesia and Pain Management Group, Department of Medicine, School of Medicine, Johns Hopkins University, Baltimore, MD 21205-2196, USA
4. National Institute of Pain, 4911 Van Dyke Road, Lutz, FL 33558, USA