1. Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, TN 37232, USA
2. Department of Biomedical Engineering, Vanderbilt University, Nashville, TN 37232, USA
3. Anesthesiology, TVHS VA Medical Center, Nashville, TN 37212, USA
4. Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, USA