The aim of this study is to evaluate the effect of intravenous magnesium sulfate on hemodynamic effects induced by blowing carbon dioxide in patients undergoing laparoscopic cholecystectomy. It is a randomized double-blind placebo-controlled clinical trial over population of patients who are candidates for laparoscopic gallbladder removal surgery. The main criterias for inclusion are, patients scheduled for laparoscopic cholecystectomy with pneumoperitoneum by CO2, aged 70-20 years, ASA class I- II, and exclusion criteria: chronic use of beta-adrenergic blockers and calcium channel blockers, the willingness of to participate in the Plan and the occurrence of comoplications. The calculated sample size is 60 (2N), patients will go under similar anesthesia. Before induction of anesthesia, in magnesium group, 50 mg/ kg of magnesium sulfate in 100 cc of normal saline and in conyrol group only 100 cc normal saline over 10 minutes will be infused. Mean arterial blood pressure and heart rate, peripheral oxygen saturation, and end expiratory carbon dioxide levels in both groups before and after induction, before pneumoperitoneum, and then every 10 minutes until 60 minutes after pneumoperitoneum will be recorded by automatic Hemodynamic monitoring. After the operation, the pain and the hemodynamic variables, postoperative shivering, nausea and vomiting, the patient's comfort during recovery, would be evaluated. After collecting and recording data, SPSS program will use to analyze and evaluate the differences between the two groups of patients.