Tracheal extubation is a critical event in the anaesthetic management of patients undergoing general anaesthesia with endotracheal intubation for elective procedures. It the state of art to provide suitable conditions for smooth extubation and avoid coughing, bucking, straining and/or laryngospasm. Several methods have been described to provide a smooth extubation, including the use of remifentanil infusion, dexmedetomidine or fentanyl. Because of its anti-inflammatory and analgesic effects and lack of respiratory depressant actions, magnesium sulphate could be an attractive alternative.

A written informed consent will be obtained from all the patients. On arrival to the preparation room intravenous cannula will be inserted, no sedation will be given. In the operating theater standard monitors, non-invasive blood pressure, oxygen saturation and electrocardiogram will be applied before induction of anesthesia, capnography after induction of anesthesia and baseline heart rate (HR), mean arterial blood pressure (MAP) and oxygen saturation (SpO2 ) will be recorded.

All patients in both groups will receive standardized anesthetic technique in the form of intravenous (i.v.) propofol 2 mg/kg, i.v. fentanyl 1-2 lg/kg and atracurium 0.5 mg/kg to facilitate endo-tracheal intubation, mechanical ventilation will be adjusted to keep end tidal carbon dioxide (EtCO2) between 30 and 35 mmHg, and all drugs will be based on ideal body weight. Isoflurane 1% in 50% oxygen and air, and 0.15 mg/kg atracurium every 20 min will be given for maintenance of anesthesia. Intraoperative HR, MAP, EtCO2 and SpO2 values will be recorded at 5- minute intervals till the end of operation. HR and MAP will be maintained within ±20% of the baseline values. Hypotension (defined as MAP < 20% of the baseline value) will be treated by a bolus of 200 ml Ringer's solution if not responding increments of 3-9 mg ephedrine will be given. Hypertension (defined as MAP > 20% of the baseline value) and/or tachycardia (defined as HR > 20% of the baseline value) a supplemental dose (25-50 µg) fentanyl will be given or increasing concentration of isoflurane. Bradycardia (HR < 50 beat per minute) persisting for >2 min will be treated with atropine, 0.4 mg i.v. boluses. Intra-operatively i.v. ondansetron, 4 mg (Zofran, GlaxoSmithKline) will be given for prevention of postoperative nausea and vomiting. After induction of anaesthesia patients will be divided into 2 groups: group C (control group) n= 30 patients will receive 10 ml of saline, then infusion of 50 ml of normal saline over one hour. Group M (magnesium group n=30 patients) will receive 1 gm of magnesium in 10 ml over 5 minutes then infusion of 1 gm in 50 ml over one hour.

By the end of surgery isoflurane will be discontinued and the residual neuromuscular block will be antagonized with neostigmine 0.05 mg/kg, given with atropine 0.02 mg/kg, the endotracheal tube will be removed after return of spontaneous breathing, and the patient will obey commands in semi-sitting position, then the patient will be transferred to the post-anesthesia care unit (PACU)

Inclusion Criteria:

• Elective surgeries that need endotracheal intubation.
• Duration of surgery 1-3 hours
• ASA Ⅰ-Ⅱ

Exclusion Criteria:

• Refusal of patients.
• Patients with hypersensitivity to the study drug.
• Patients with cardiac disorders, bundle branch block, hart block
• Neuromuscular disease, calcium channel blocker medication or hypermagnesemia