[1] Univ Ottawa, Dept Emergency Med, Clin Epidemiol Program, Emergency Med,Ottawa Hosp Res Inst, Ottawa, ON, Canada
[2] Univ Ottawa, Dept Emergency Med, Clin Epidemiol Program, Epidemiol & Community Med,Ottawa Hosp Res Inst, Ottawa, ON, Canada
[3] Univ Ottawa, Dept Emergency Med, Clin Epidemiol Program, Ottawa Hosp Res Inst, Ottawa, ON, Canada
[4] Univ Ottawa, Dept Emergency Med, Clin Epidemiol Program, Ottawa Hosp Res Inst,Dept Emergency Med, Ottawa, ON, Canada
[5] Queens Univ, Dept Emergency Med, Emergency Med, Kingston, ON, Canada
[6] Queens Univ, Dept Emergency Med, Pharmacol & Toxicol, Kingston, ON, Canada
[7] Queens Univ, Dept Pharmacol & Toxicol, Emergency Med, Kingston, ON K7L 3N6, Canada
[8] Queens Univ, Dept Pharmacol & Toxicol, Pharmacol & Toxicol, Kingston, ON K7L 3N6, Canada
[9] Univ Alberta, Dept Emergency Med, Edmonton, AB, Canada
[10] Univ Alberta, Dept Emergency Med, Emergency Med, Edmonton, AB, Canada
[11] Univ Laval, Dept Emergency Med, Quebec City, PQ G1K 7P4, Canada
[12] Univ Ottawa, Clin Epidemiol Program, Ottawa Hosp Res Inst, Ottawa, ON, Canada
[13] Univ British Columbia, Dept Emergency Med, Vancouver, BC V5Z 1M9, Canada
[14] McMaster Univ, Div Emergency Med, Hamilton, ON, Canada
[15] Univ Toronto, Div Emergency Med, Toronto, ON, Canada
[16] Univ Western Ontario, Div Emergency Med, London, ON, Canada
[17] Univ Manitoba, Dept Emergency Med, Winnipeg, MB, Canada
[18] Univ Ottawa, Div Neurosurg, Clin Epidemiol Program, Ottawa Hosp Res Inst,Consulting Neurosurg, Ottawa, ON, Canada
[19] Univ Ottawa, Dept Epidemiol & Community Med, Clin Epidemiol Program, Ottawa Hosp Res Ins,Biostat & Epidemiol, Ottawa, ON, Canada