Heidi Vanhala1, Eija Junttila2, Teemu Luoto3. 1. Department of Anesthesia and Intensive Care, Tampere University Hospital, PL 2000, 33521, Tampere, Finland. heidi.vanhala@pshp.fi. 2. Department of Anesthesia and Intensive Care, Tampere University Hospital, PL 2000, 33521, Tampere, Finland. 3. Department of Neurosurgery, Tampere University Hospital and Tampere University, Tampere, Finland.