الفهرس 
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Abstract
This prospective clinical randomized study was carried out sixty adult patients undergoing elective major abdominal or pelvic surgery under general anesthesia at Mansoura University Hospitals.
Patients with renal, hepatic, cardiovascular, neurological or muscular dysfunction. Also diabetic patients, obese and patients treated with calcium channel blockers, or having increased serum magnesium level before operation were excluded from the study. Patients were randomly allocated into three equal groups (n=20): Control group: patients received normal saline 0.9% solution (placebo) intravenously slowly before induction of anesthesia, followed by infusion of isotonic sodium chloride solution by means of syringe pump over the entire operation period and continued for two hours postoperatively.
Low dose group: patients received MgSo4 in a dose of 20 mg/kg slowly intravenous before induction of anesthesia, followed by MgSo4 infusion at a rate of 6 mg/kg/h by means of syringe pump over the entire operation period and continued for two hours postoperatively.
High dose group: patients received MgSo4 in a dose of 40 mg/kg slowly intravenous before induction of anesthesia, followed by MgSo4 infusion at a rate of 12 mg/kg/h by means of syringe pump over the entire operation period and continued for two hours postoperatively. Patients premedicated intravenously with 0.02 mg/kg atropine and 0.04 mg/kg midazolam. For three studied groups; induction by thiopental sodium in a dose of 5 mg/kg and 1g/kg fentanyl. Tracheal intubation was facilitated by vecronium in a dose of 0.1 mg/kg. Patients lungs were mechanically ventilated to keep endtidal CO2 35 mmHg. Anesthesia was maintained by 1% isoflurane and 60% nitrous oxide in oxygen. At the end of surgery, antagonism of neuromuscular blockade was achieved with intravenous mixture of 0.03 mg/kg prostigmine and 0.01 mg/kg atropine Hemodynamics and relaxographic data (for calculation of clinical duration of bolus dose and total dose requirement of vecronium in mg/kg) were monitored. Blood levels of cortisone, glucose, magnesium and calcium at basal value in preoperative period before MgSo4 injection, immediate after laryngoscopy and endotracheal intubation, one hour after endotracheal intubation and after the end of surgery were measured. Postoperatively, sedation (4point rating scale), pain (visual analogue scale) and dose & time of analgesic requirement were assessed for all patients. Our results administration of 40 mg/kg bolus of magnesium sulphate followed by 12 mg/kg/h infusion perioperatively attenuated stress response of induction secondary to laryngoscopy and endotracheal intubation and maintained favorable hemodynamic stability during anesthesia and surgery. In addition, it reduced intraoperative muscle relaxants dosage with intensified its action and good adjuvant to perioperative analgesic management as preemptive analgesic agent. So, magnesium sulphate could be of interest as an adjuvant to general anesthesia of major operations.