 1. Anaesthesia co-induction sedation with fentanyl 2-5 ugkg and midazolam 0.025- 0.05mgkg. Following induction of anaesthesia, patients will be maintained on a combined intravenous infusion of fentanyl 1.5 ugkghr and midazolam 0.025-0.05 mgkghr with Fi021. 