 Peri-operative monitoring LiDCOTM CNAP and BIS monitoring were attached prior to induction of anaesthesia in the anaesthetic room of the operating theatre. A standardised anaesthetic technique was used for every participant, consisting of propofol induction, sevoflurane maintenance to a target BIS 40-60 and opioid analgesia with fentanyl. Participants underwent positive pressure ventilation to a tidal volume of 8mlkg. 