The effect of clonidine on sevoflurane requirements for anaesthesia and hypnosis

We evaluated the effects of clonidine given orally on sevoflurane requirements for anaesthesia and hypnosis. Patients received either clonidine (5 mu g.kg(-1)) by mouth (n = 21) 90 min before surgery or no premedication (n = 21) by random allocation. MAC was calculated using repeated tetanic nerve stimulation with end-tidal sevoflurane concentration increased or decreased by 0.3 vol.% depending on the previous response. MAC awake was calculated according to the response to verbal command. The mean (SD) MAC in the clonidine-treated patients was 1.53 (0.20)% compared with 1.83 (0.15)% in the control group (p < 0.001). Similarly, MAC awake was reduced in the clonidine group (0.50 (0.08)% compared with 0.60 (0.07)% in the control group) (p < 0.001). We conclude that clonidine 5 mu g.kg(-1) orally administered pre-operatively reduces sevoflurane requirements for anaesthesia and hypnosis.