Effects of magnesium sulphate and clonidine on propofol consumption, haemodynamics and postoperative recovery

Background. This placebo-controlled, double-blind study wasdesigned to assess the effects of magnesium sulphate and clonidineon peroperative haemodynamics, propofol consumption and postoperativerecovery. Methods. Sixty ASA I–II patients undergoing spinal surgerywere randomized into three groups. Group M received magnesiumsulphate 30 mg kg^–1 as a bolus before induction and 10mg kg^–1 h^–1 by infusion. Group CL received clonidine3 µg kg^–1 as a bolus before induction and 2 µgkg^–1 h^–1 by infusion during the operation period.The same volume of isotonic solution was administered to thecontrol group (group CT). Anaesthesia was induced with propofoland was maintained with propofol infusion [dose according tothe bispectral index (BIS)], fentanyl and cisatracurium. Analysisof variance and the Bonferroni test were used for statisticalanalysis. Results. Induction of anaesthesia with propofol was rapid inthe presence of magnesium sulphate and clonidine. The time forBIS to reach 60 was significantly shorter in group M and groupCL (P<0.0001) but postoperative recovery was slower withmagnesium sulphate compared with the clonidine and control groups(P<0.0001). There was no statistical difference in heartrate and arterial blood pressure between the groups. Propofolrequirements for induction and maintenance of anaesthesia weresignificantly lower with magnesium and clonidine (P<0.0001). Conclusion. Clonidine caused bradycardia and hypotension andmagnesium sulphate caused delayed recovery, but can be usedas adjuvant agents with careful management.