Background: This placebo-controlled, double-blind study was designed to assess the effects of magnesium sulphate and clonidine on peroperative haemodynamics, propofol consumption and postoperative recovery.
Methods: Sixty ASA I-II patients undergoing spinal surgery were randomized into three groups. Group M received magnesium sulphate 30 mg kg(-1) as a bolus before induction and 10 mg kg(-1) h(-1) by infusion. Group CL received clonidine 3 microg kg(-1) as a bolus before induction and 2 microg kg(-1) h(-1) by infusion during the operation period. The same volume of isotonic solution was administered to the control group (group CT). Anaesthesia was induced with propofol and was maintained with propofol infusion [dose according to the bispectral index (BIS)], fentanyl and cisatracurium. Analysis of variance and the Bonferroni test were used for statistical analysis.
Results: Induction of anaesthesia with propofol was rapid in the presence of magnesium sulphate and clonidine. The time for BIS to reach 60 was significantly shorter in group M and group CL (P<0.0001) but postoperative recovery was slower with magnesium sulphate compared with the clonidine and control groups (P<0.0001). There was no statistical difference in heart rate and arterial blood pressure between the groups. Propofol requirements for induction and maintenance of anaesthesia were significantly lower with magnesium and clonidine (P<0.0001).
Conclusion: Clonidine caused bradycardia and hypotension and magnesium sulphate caused delayed recovery, but can be used as adjuvant agents with careful management.