Reduction Perioperative Bleeding in Laminectomy With Instrumentation or More Than or Equal to 3 Levels Laminectomy: The Comparison Between Placebo, and Double Doses of Tranexamic Acid (15 mg/kg and 15 mg/kg)

78 patients undergoing major laminectomy (with instrumentation or equal or more than 3 levels laminectomy) will be enrolled. We exclude patients who age over 65, anemia, allergy to tranexamic acid, history of deep vein thormbosis (DVT), ischemic heart disease (IHD), pulmonary embolism (PE), strokes, liver disease, chronic kidney disease with creatinine >2.0 mg/dl, and coagulopathy. After randomization, before induction and 3 hour after the first dose, patients will receive study drug or placebo intravenously. The standard anesthesia and monitoring will be tha same for all of the patients. Perioperative mild hypotensive technique will be used with the mean arterial pressure more than 60 mmHg and nearly the end, the blood pressure will be back to normal for the bleeding check. Hematocrit will be monitored at the begining and every two hours. Blood will be given if the hematocrit is below 30%. The perioperative fluid will be managed by anesthesiologist who will not know the patients' groups. The next morning, the hematocrit and blood creatinine will be checked and if the hematocrit is lower than 30%, blood will be given. Perioperative blood loss, total fluid and blood transfusion within 24 hours will be recorded. If there are any suspected symptoms and signs of DVT, angina, CHF, PE, strokes or other complications, the necessory investigations will be done for the definite dignosis and the appropriate treatment will be started immediately.