Study aim: Effect of oral clonidine on bleeding rate in lumbar laminectomy Design: 100 patients that meet the inclusion criteria after surgery finished and the patient is discharged from anesthesia will be selected as research sample and then divided into intervention and control groups with binary blocking.The intervention group will receive clonidine and the control group will receive placebo. The study is a randomized, double-blind,placebo-controlled clinical trial. Settings and conduct: Patients will be randomly divided into two groups according to the random number table.The intervention group received 0.5 mg clonidine and the control group received the same amount of placebo half an hour before surgery. Given that the study is double-blind. Both clonidine and placebo medications will be prepared each morning by the number of surgeries and number required by the plan's administrator. Envelope A contains oral clonidine and envelope B is a placebo. Each patient will receive the envelopes based on whether they are A or B coded by an anesthetist who is blinded of the type of drug.Intraoperative bleeding will then be assessed according to the amount of suction device filling and the surgeon's satisfaction with the operative field bleeding.In this study patient and anesthesiologist is blinded. Participants/Inclusion and exclusion criteria: Entry requirements:All ASA I & II class patients aged 18-60 years Exclusion criteria: Diabetic patients; Patients with systemic diseases(cardiovascular, pulmonary, liver and kidney,...) ; Use medicines Interfering with clonidine Intervention groups: The intervention group received 0.2 mg clonidine orally with water and control group receive placebo similar to first group half an hour before starting of surgery. Main outcome variables: The effect of clonidine on intraoperative hemorrhage by evaluation of suction device filling and field operation (low, moderate, high)