الفهرس 
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Abstract
Summary We have done a comparative, randomized and double blind study to to compare between the role of oral Clonidine and Atenolol in providing optimal surgical field and decreasing blood loss in spine fusion surgeries under general anaesthesia.
A total of 50 patients, ASA grade I-II, scheduled for elective fusion of the lumbar spine at Beni-Suef university hospital were enrolled in the study.
They were allocated randomly into two groups according to an opaque sealed envelope technique in a double-blind manner to 2 groups with 25 patients in each to receive drugs as follows:
group (A): receive 1 tablet of atenolol (50 mg) 90 minutes before entering the operating room.
group (C): receive 1 tablet of clonidine (150 μg) 90 minutes before entering the operating room.
Patients in both groups received 7 mL/kg of Ringer’s solution before induction of anesthesia and were monitored by the same system for heart rate (HR) and mean arterial Blood pressure (MABP) (invasive and noninvasive). Electrocardiography, pulse oximetry, end-tidal CO2, and urine output was also monitored. After intravenous premedication with 0.05 mg/kg Midazolam and 2 μg /kg Fentanyl, anaesthesia was induced with 2 mg/kg Propofol and 0.5 mg/kg Atracurium, The patients were intubated after 3 minutes. Anaesthesia was maintained by atracurium 10 mg every 20 minutes and Isoflurane (1.5%). When it was not enough to induce the target hypotension (MABP 60-70), a Nitroglycerine infusion was added to the regimen. All patients were positioned (in the prone position) and operated on by the same team. Positioning of all patients was performed using the same system and type of rolls (chest and pelvic rolls, leaving the abdomen free).
The mechanical ventilation setting for all patients was set as follows: tidal volume = 7-8 mL/kg, respiratory rate 12/min and inspiration/expiration ratio = 1:2 ; then, according to end-tidal CO2, only tidal volume was changed to maintain end tidal CO2 between 30-35 mm Hg (normocarbia).
The following data were recorded for each patient: age, sex, weight, operation time. Heart rate and MABP were recorded before( baseline ) and after induction, immediately after intubation, every 5 minutes for 15 minutes and then every 15 minutes till end of surgery and every 50 minutes for 4 hours in recovery room . Need for Nitroglycerin infusion for induced hypotension and its total dose was calculated, Intraoperative blood loss and surgeon satisfaction. Surgeon satisfaction with a bloodless field was evaluated as follows: good (minimal or no bleeding), intermediate (modest bleeding and impairment of operating condition), and bad (significant bleeding and impairment of operating conditions) .Occurrence of side effects (hypotension and bradycardia).
The result of the study showed that group A significantly reduced MAP and HR than group C, but there was no significant difference in reducing blood loss between both groups.
So we concluded that the use of oral atenolol and oral clonidine provided optimal surgical field in spine fusion surgeries under general anaesthesia, however atenolol was superior to clonidine.