[1] Queen Elizabeth 2 Hlth Sci Ctr, Dept Med, Halifax, NS, Canada
[2] Kingston Gen Hosp, Dept Med, Kingston, ON K7L 2V7, Canada
[3] McMaster Univ, Dept Med, Hamilton, ON L8S 4L8, Canada
[4] McMaster Univ, Dept Clin Epidemiol & Biostat, Hamilton, ON L8S 4L8, Canada
[5] St Pauls Hosp, Program Crit Care Med, Vancouver, BC V6Z 1Y6, Canada
[6] St Pauls Hosp, Ctr Hlth Evaluat & Outcomes Sci, Vancouver, BC V6Z 1Y6, Canada
[7] Univ British Columbia, Vancouver, BC V5Z 1M9, Canada
[8] Univ Alberta, Dept Publ Hlth Sci, Edmonton, AB T6G 2M7, Canada
[9] Univ Alberta, Div Crit Care Med, Edmonton, AB T6G 2M7, Canada
[10] Queens Univ, Dept Epidemiol & Community Hlth, Kingston, ON K7L 3N6, Canada