[1] UNIV HELSINKI,CENT HOSP,DEPT ANAESTHESIOL,SF-00260 HELSINKI 26,FINLAND
[2] UNIV HOSP TRONDHEIM,DEPT ANAESTHESIOL,TRONDHEIM,NORWAY
[3] HAUKELAND HOSP,DEPT ANAESTHESIOL,N-5016 BERGEN,NORWAY
[4] OULU UNIV,CENT HOSP,DEPT ANAESTHESIOL,OULU,FINLAND
[5] GOTHENBURG UNIV,SAHLGRENS HOSP,DEPT ANAESTHESIOL,S-41345 GOTHENBURG,SWEDEN
[6] BORGARSPITALINN,DEPT ANAESTHESIOL,REYKJAVIK,ICELAND
[7] UNIV COPENHAGEN,RIGSHOSP,DEPT ANAESTHESIOL,DK-2100 COPENHAGEN,DENMARK