This randomized, double-blind clinical trial study, was performed during 2014-15 on 120 patients undergoing spine surgery. Inclusion criteria were as follows: age range of 20 to 50 years, ASA class 1 or 2 and spine surgery candidates. Exclusion criteria included patients with hypertension, diabetes, clotting problems, ischemic heart disease, drug or alcohol abuse, pregnancy, taking beta blockers or calcium channels blockers drugs and operating time of over 120 minutes. Patients were randomly divided into three groups. The first group took an oral clonidine 0.2 mg tablet 30 minutes before entering the room and 100cc saline as placebo 15 minutes before induction of anesthesia. The second group received placebo pills and 0.5 µ/kg dexmedetomidine 15 minutes before induction of anesthesia in 100cc saline infusion with continuation rate of 0.25µ/h. The third group received placebo tablets plus 100cc saline infusion taken 15 minutes before induction of anesthesia. All three groups underwent general anesthesia with fentanyl 3.0 μg/kg, thiopental 3-5 mg/kg, atracurium 0.5 mg/kg. Maintenance of anesthesia was done with 0.5-1% isoflurane, 50% N2O and 50% O2. During surgery the anesthesiologist, by calculating the amount of required fluid, administrated the sufficient volume of crystalloid to the patients.
Heart rate, systolic blood pressure and diastolic arterial pressure before induction of anesthesia were registered as a baseline using the designated arterial line one minute after intubation and subsequently 10, 20, 30 minutes after induction of anesthesia and after extubation. The amount of intraoperative blood loss of each patient was estimated based on the volume of blood in the suction bottle and the number of the bloody gauze pads.