In this study, the effect of magnesium sulphate on the onset and duration of intense and moderate cis-atracurium induced neuromuscular blocking and on the period of no response to nerve stimulation will be evaluated in patients who will recieve magnesium sulphate (intervention group) and patients who will not recieve magnesium sulphate (comparator group).

General anesthesia is a drug-induced reversible state consisting of unconsciousness, amnesia, anti-nociception, and immobility, with maintenance of physiological stability. Balanced general anesthesia, the most common management strategy used in anesthesia care, entails administering a combination of different agents to create the anesthetic state. There is evidence that balanced general anesthesia uses less of each drug than if the drug were administered alone. This approach is believed to increase the likelihood of a drug's desired effects and reduce the likelihood of its side effects. With addition of adjuvants, Alpha-2 adrenoceptor agonists, such as dexmedetomidine, are known to possess amnesic, analgesic, sympatholytic, and antinociceptive properties, and therefore, can reduce the requirement of anesthetics and opioids intraoperatively. Administration of MgSO4 has also shown significant reduction in the perioperative requirement of propofol, opioids, and muscle relaxants. Magnesium sulphate has gained prominence as an adjuvant drug in multimodal anesthesia and pain medicine. It has several clinical indications including attenuation of the adrenergic response to tracheal intubation and improved peri-operative analgesia. Magnesium sulphate also enhances the action of non-depolarizing neuromuscular blocking drugs, resulting in potentiation of neuromuscular blockade (NMB).The site of magnesium potentiation of neuromuscular blocking drugs is the motor end plate, where magnesium reduces the release of prejunctional acetylcholine, thereby decreasing the muscle membrane excitability. However, limited data exist concerning the effect of magnesium sulphate on the duration of deep or intense NMB and on the period of no response to nerve stimulation.

Inclusion Criteria:

• Age group 18-60 years old
• Both genders
• Patients who will be scheduled to undergo elective otorhinolaryngological surgery.
• Patients with BMI between 18.5 and 24.9 Kg/m2.
• Patients with American Society of Anesthesiologist physical status classification of 1 or 2

Exclusion Criteria:

• Patients who are less than 18 years old or more than 60 years old.
• Patients on medications that interfered with muscle activity.
• Allergy to medications used in this study.
• Pregnancy or suspected pregnancy.
• Neuro-muscular diseases.
• Renal or hepatic impairment.
• Hypermagnesemia (>2.5 mmol) or hypomagnesemia (<1.7 mmol).
• Patients refusing to study

Allocation numbers will be placed in opaque envelopes and opened by an anesthesiologist (not participating in the study)who will also prepare the study solutions. The solutions used in the study are similar in physical appearance and an investigator not included in the study will prepare the solutions.