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.