J L Walters1, T Jackson1, D Byrne2, K McQueen1. 1. Department of Anesthesia and Pain Medicine, Vanderbilt Interventional Pain Clinic, Vanderbilt University Medical Center, One Hundred Oaks, 719 Thompson Lane, Suite 22209, Nashville, TN 37204, USA. 2. Department of Anesthesia and Pain Medicine, Vanderbilt Interventional Pain Clinic, Vanderbilt University Medical Center, One Hundred Oaks, 719 Thompson Lane, Suite 22209, Nashville, TN 37204, USA david.a.byrne@vanderbilt.edu.