From the Departments of Anesthesiology (E.M.S.L., C.A.W., P.T.) and Obstetrics and Gynecology (W.A.G.) and Center for Healthcare Studies (W.A.G., P.T.), Northwestern University Feinberg School of Medicine, Chicago, Illinois; Departments of Anesthesiology (S.S.) and Biostatistical Sciences (G.B.R.), Wake Forest Baptist Medical Center, Winston-Salem, North Carolina; Department of Anesthesiology, University of Michigan, Ann Arbor, Michigan (C.P.); and Department of Anesthesia, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa (C.A.W.).