In the preoperative period, a written informed consent from the patient or their kins will be obtained after a detailed explanation of the study. Randomisation of subjects into 2 groups will be done using a computer-based simple randomisation method. Allocation concealment will be done using a serially numbered opaque sealed envelope technique. During the pre-anaesthetic check-up on the day before surgery, the APAIS anxiety score will be evaluated and noted (X1). On the day of surgery, after an adequate fasting period, the patient will be administered Tab. Melatonin 6 mg with sips of water in the study group (M) or a placebo in the control group (C). Ninety minutes before shifting to OT, the study drug would be given by a qualified health care personnel [nurse] to whom the opaque sealed envelope will be given. Before shifting inside OT, APAIS will be assessed again (X2). Inside the operation theatre, standard ASA monitoring (5 lead electrocardiograph (ECG), non-invasive blood pressure (NIBP), and pulse oximeter (SpO2) along with cerebral oximeter and nasopharyngeal temperature probe will be attached. Baseline blood pressure, pulse and regional cerebral saturation (rSO2) will be recorded. After induction of anaesthesia and intubation, vitals will be recorded every 15 minutes. Anaesthesia will be maintained with air/oxygen mixture (1:1) at flow rate of 2 litres/min along with fentanyl infusion 1 mcg/kg/hr and Propofol infusion 100 mcg/kg/min, titrated to effect. Intraoperative neuromuscular blockade will be maintained with rocuronium 0.2 to 0.3 mg/kg/hr infusion. Before the opening of dura, 20% mannitol at a dose of 1 g/kg will be infused over 20 minutes in all patients. Throughout the surgery End tidal CO2 will be maintained in the range of 30-35 mmHg. At the completion of surgery, time to emergence and time to extubation will be recorded after administration of reversal agent. Patients not extubated for any reason will be excluded from the study.