Two peripheral venous lines (18G/20G catheter) will be secured. Invasive vascular access (arterial line for direct continuous blood pressure assessment, central venous catheter) will be secured as per the requirement of surgery and/or patients morbid status. A BIS sensor (Covidien IIc, Mansfield, USA) for monitoring depth of anaesthesia, using the BIS monitoring module (Model DSC-XP, Aspect medical system, USA), will be applied over the patient's forehead according to manufacturer's instruction prior to induction of anaesthesia.