[Effects clonidine and midazolam on anaesthetic requirements].

Background: Premedication reduces requirement for anaesthestic agents during anaesthesia. There have been few papers published on the effects of clonidine on the MAC of volatile agents. The aim of this study was to assess the effects of premedication with midazolam or clonidine on remifentanil and sevoflurane requirements, necessary to achieve an adequate level of anaesthesia, in patients undergoing laparoscopic cholecystectomy.

Methods: ASA I and II patients were randomly allocated to three groups. Two groups received premedication with either 150 mg of clonidine, or 7.5-15 mg of midazolam. The third group received a placebo. All patients were induced with remifentanil and sevoflurane, and intubated after relaxation with rocuronium. The sevoflurane concentration was adjusted to achieve entropy values between 60 and 50. Analgesia was maintained with remifentanil via infusion at a rate of 0.05-0.15 microg kg(-1) min(-1).

Results: Sixty patients were enrolled to the study. The concentration of sevoflurane necessary to maintain entropy between 55 and 60 was statistically lower in the midazolam group than in the placebo group (p = 0.006) or the clonidine group (p = 0.02). No statistically significant differences in remifentanil requirements were observed. The recovery time was shortest in the placebo group (p < 0.05), slightly longer in the clonidine group (p > 0.05), and longest in the midazolam group (p < 0.05).

Conclusions: Clonidine did not affect the MAC of sevoflurane and remifentanil requirement. Midazolam decreased the time taken for induction of anaesthesia.