[1] Seespital Horgen, Dept Anaesthesia, Zurich, Switzerland
[2] Hosp Francisco Gentil, Dept Anaesthesia, Porto, Portugal
[3] Univ Hosp Balgrist, Dept Anaesthesia, Zurich, Switzerland
[4] Cantonal Hosp, Dept Visceral Surg, Bellinzona, Switzerland
[5] Cantonal Hosp, Dept Anaesthesia, Bellinzona, Switzerland
[6] Stadtspital, Dept Anaesthesia, Zurich, Switzerland