Patients were randomized to receive either intravenous ketorolac 30 mg in bolus followed by saline infusion (Group K), intravenous magnesium sulfate 20 mg/kg in bolus followed by magnesium 2 mg/kg/h (Group M) or intravenous saline solution 20 ml in bolus followed by saline infusion during the entire procedure (Group S). The study use a double-blinded methodology with random allocation into three groups using sealed opaque envelopes numbered 1 to 60, containing the instructions for the study. An independent anesthesiologist not involved in the study prepared the solutions and an observer who was also blinded to the patient's group records the data.