Anaesthesia is maintained by aiming at a Bispectral Index between 40 and 60. The investigators start with Propofol 2 % at an infusion rate of 25 % of total body weight (5 mg/kg/hr), with the ability to change when the aimed BIS is not reached. Remifentanyl (2 mg Remifentanyl in 40 ml of NaCl 0.9 %) and Atracurium (150 mg of Atracurium in 50 ml of NaCl 0.9 %) are standardised at infusion rates of 25 % of ideal body weight and 10 % of total body weight respectively.