Magnesium and Ketamine in Postoperative Analgesia

"Patients will be assigned into 2 groups (each of 45):~Ketamine group (group K): will receive a bolus of 0.5 mg/kg ketamine during induction of anaesthesia diluted in 100 ml normal saline, followed by ketamine infusion 0.12 mg/kg/hour continued till 24 hours after surgery. The infusion pump concentration will be 0.6mg/ml and the rate of infusion will be 0.2 ml/kg/hour."

Ketamine and magnesium group (group KM): will receive a bolus of 0.5 mg/kg ketamine added to 50mg/kg magnesium sulfate diluted in 100 ml normal saline over 30 minutes after induction of anaesthesia, followed by ketamine infusion 0.12 mg/kg/hour added to 8mg/kg/hour of magnesium sulfate continued till 24 hours after surgery. Each ml of the administered infusion will contain 0.6mg ketamine and 40mg magnesium and the rate of infusion will be 0.2 ml/kg/hour.