[1] Queens Univ, Dept Surg, Kingston, ON, Canada
[2] Queens Univ, Dept Epidemiol & Community Hlth, Kingston, ON, Canada
[3] Queens Univ, Dept Med, Kingston, ON K7L 3N6, Canada
[4] Kingston Gen Hosp, Clin Evaluat Res Unit, Kingston, ON K7L 2V7, Canada
[5] Univ Colorado, Sch Med, Dept Anesthesiol, Denver, CO USA
[6] Ottawa Hosp, Dept Surg, Ottawa, ON, Canada
[7] Ottawa Hosp, Dept Crit Care, Ottawa, ON, Canada
[8] Univ Ottawa, Ottawa, ON, Canada
[9] Univ Alberta, Div Crit Care Med, Edmonton, AB, Canada