preoperative melatonin, pregabalin or both will be given to all patients preoperative

On arrival at the operating room, continuous electrocardiogram, non-invasive blood pressure and pulse oximetry monitors will be applied. Sedation score (ramsay sedation score)(10) will be recorded on arrival to OR An 18-gauge cannula will be inserted in a peripheral vein and a warmed (37°C) lactated Ringer solution infusion was started. Ondansetron 4 mg will be administered intravenously as a prophylaxis against nausea and vomiting. Thereafter the patient will be supported in the sitting position. Intrathecal anaesthetic (room temperature hyperbaric bupivacaine 0.5% (20 mg) + fentanyl 25 μg (0.5 mL) will be given under complete aseptic technique . The patient was returned to the supine position for 15 min then to lateral position with operative side up.

HR and blood pressure will be measured every 2.5 minutes intraoperatively, however, the values will be recorded in the anesthesia chart only every five minutes for 2 hours then every 15 minutes for 3 hours. Durations will be calculated considering the time of spinal injection as time zero.

Hypotension (SAP<100 mmHg or <80% of the baseline measured before spinal anaesthesia) will be treated by ephedrine 6 mg, to be repeated if inadequate response within 2 minutes. If bradycardia (HR≤60 bpm) developed, atropine (0.6 mg) will be given to restore adequate HR (≥60 bpm).

Inclusion Criteria:

• ASA I or II
• patients undergoing hip arthroplasty
• patient consent for spinal anaesthesia
• patient alert, concious and good mental condition

Exclusion Criteria:

• Patients with any neurolgical or psychiatric history before the procedure
• Patients with a history of chronic pain
• patients with known allergy to any of this study drugs
• patients have Any contraindication to neuraxial block.