[1] Univ Nebraska Med Ctr, Dept Surg, Omaha, NE 68154 USA
[2] Creighton Univ, Dept Surg, Omaha, NE 68131 USA
[3] VA Nebraska & Western Iowa Hlth Care Syst, Dept Surg, Omaha, NE 68154 USA
[4] VA Nebraska & Western Iowa Hlth Care Syst, Div Patient Safety & Qual Improvement, Omaha, NE 68154 USA
[5] Creighton Univ, Biostat Core, Omaha, NE 68131 USA