[1] Univ Copenhagen, Dept Anaesthesiol, Herlev Hosp, DK-1168 Copenhagen, Denmark
[2] Rishosp, Dept Anaesthesiol, Juliane Marie Ctr, Copenhagen, Denmark
[3] Rishosp, Dept Obstet, Juliane Marie Ctr, Copenhagen, Denmark
[4] Rigshosp, Capital Reg Blood Bank, DK-2100 Copenhagen, Denmark