[1] Univ Calif Davis, Davis Hlth Syst, Dept Emergency Med, Sacramento, CA 95817 USA
[2] Univ Calif Los Angeles, David Geffen Sch Med, Dept Emergency Med, Los Angeles, CA 90095 USA
[3] Ronald Reagan UCLA Med Ctr, Dept Emergency Med, Los Angeles, CA USA
[4] Harbor UCLA Med Ctr, Dept Emergency Med, Torrance, CA 90509 USA