[1] Med Coll Wisconsin, Dept Surg, Div Trauma & Crit Care, Milwaukee, WI 53226 USA
[2] Univ Minnesota, Dept Surg, Div Trauma & Crit Care, Minneapolis, MN USA
[3] Univ N Carolina, Dept Surg, Div Trauma & Crit Care, Chapel Hill, NC USA
[4] Univ Minnesota, Dept Internal Med, Div Pulm & Crit Care, Minneapolis, MN USA
[5] Univ Minnesota, Sch Publ Hlth, Div Biostat, Minneapolis, MN USA