作者单位:Stanford Hlth Care, Dept Anesthesiol, Stanford, CA USA[1]Stanford Univ, Sch Med, Stanford Law Sch, Stanford, CA USA[2]John Muir Hlth Walnut Creek Med Ctr, Dept Anesthesiol, Walnut Creek, CA USA[3]Univ Arkansas Med Sci, Dept Anesthesiol, Little Rock, AR 72205 USA[4]