[1] Washington Univ, Sch Med, Div Lab Med, Dept Med & Pathol, St Louis, MO 63110 USA
[2] Washington Univ, Sch Med, Dept Anesthesia, St Louis, MO 63110 USA
[3] Washington Univ, Sch Med, Dept Orthoped, St Louis, MO 63110 USA
[4] Univ Florida, Coll Med, Dept Anesthesiol, Gainesville, FL USA