EFFECT OF CLONIDINE AND DEXMEDETOMIDINE PREMEDICATION ON PERIOPERATIVE OXYGEN-CONSUMPTION AND HEMODYNAMIC STATE

Premedication has been shown to affect both oxygen consumption and met abolic rate. We have compared the perioperative metabolic and haemodyn amic effects of two alpha(2)-agonists, clonidine and the more selectiv e dexmedetomidine, in 30 ASA I patients undergoing plastic surgical pr ocedures under general anaesthesia. Patients were premedicated with cl onidine 4 mu g kg(-1) (n=10), dexmedetomidine 2.5 mu g kg(-1) (n=10) o r saline (n=10) i.m. The doses of clonidine and dexmedetomidine were i ntended to be equipotent. The maximum decrease in preoperative oxygen consumption was 8% and decreases in systolic and diastolic arterial pr essures were 11% from baseline after clonidine and dexmedetomidine. Du ring operation, the maximum reduction in heart rate was 18% in the clo nidine and dexmedetomidine groups compared with the placebo group. Aft er operation, the maximum decrease in systolic arterial pressure was 1 1%, diastolic arterial pressure 15% and oxygen consumption 17% in the clonidine and dexmedetomidine groups compared with placebo. In summary , both clonidine 4 mu g kg(-1) and dexmedetomidine 2.5 mu g kg(-1) dec reased perioperative oxygen consumption effectively, with a similar ha emodynamic profile.