The effect of clonidine on desflurane consumption using bispectral index monitoring during general anaesthesia: Randomised, double- -blind, placebo controlled study.

Objective: This study was designed to test the hypothesis that clonidine deepens general anaesthesia as measured by the bispectral index (BIS) and allows the dose of desflurane to be reduced. Design: Randomised, double-blind, placebo controlled study. Setting: Department of Anaesthesia and Intensive Care of Regional and District General Hospital. Materials and methods: Fifty patients undergoing general anaesthesia for elective total hip or total knee replacement were randomly allocated into two groups. The treatment group had 2 μg . kg-1 clonidine administered intravenously 10 minutes before general anaesthesia induction and the control group was given an intravenous placebo. Depth of anaesthesia was guided by BIS with a target level between 40 and 60. The consumption of desflurane during anaesthesia was measured. After stopping desflurane administration at the end of surgery, time to return of consciousness (ROC) was recorded. Unpaired t-test was used for statistical analyses. Results: Twenty five patients with clonidine and 25 with placebo were enrolled. The consumption of desflurane was significantly lower in the clonidine group - 33.1 ± 5.0 g, vs. the placebo group -44.5 ± 10.6 g (p < 0.001). No difference was found in the average time to ROC. This was 6.4 ± 3.8 min in the clonidine group vs. 6.2 ± 3.7 min in the placebo group (p = 0.822). Conclusion: Intravenous clonidine decreases the consumption of desflurane during general anaesthesia. This sparing effect is not associated with increased time to ROC. [ABSTRACT FROM AUTHOR]