Andrea L Nicol1, Honorio T Benzon2, Benjamin P Liu3. 1. Department of Anesthesiology, University of Kansas Medical School, Kansas City, Kansas, U.S.A.. anicol@kumc.edu. 2. Department of Anesthesiology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, U.S.A. 3. Department of Radiology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, U.S.A.