[1] Klinikum Bruderwald, Dept Anesthesia, Bamberg, Germany
[2] Kantonsspital Baden, Dept Anesthesia, CH-5404 Baden, Switzerland
[3] Univ Helsinki, Cent Hosp, Toolo Hosp, Dept Anesthesia, Helsinki, Finland
[4] Univ Helsinki, Cent Hosp, Jorvi Hosp, Dept Anesthesia, Helsinki, Finland
[5] Univ Hosp Aachen, Dept Anesthesia, Aachen, Germany
[6] Univ Alberta, Div Prevent Med, Edmonton, AB, Canada