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The influence of the α2-adrenoceptor agonist, clonidine, on the EEG and on the MAC of isoflurane

Published online by Cambridge University Press:  16 August 2006

H. M. M. El-Kerdawy ,
E. E. Van Zalingen  and
J. G. Bovill
H. M. M. El-Kerdawy
Affiliation:
Department of Anaesthesiology, Leiden University Medical Centre, Leiden, The Netherlands Present address: Department of Anaesthesia, University of Cairo, Cairo, Egypt.
E. E. Van Zalingen
Affiliation:
Department of Anaesthesiology, Leiden University Medical Centre, Leiden, The Netherlands
J. G. Bovill
Affiliation:
Department of Anaesthesiology, Leiden University Medical Centre, Leiden, The Netherlands
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Abstract

We investigated the influence of intravenous clonidine 2, 4 and 6 μg kg−1 on the electroencephalogram and on the minimal alveolar concentration of isoflurane in 40 patients aged 20–60 years undergoing elective surgery. Minimal alveolar concentration was determined using the Dixon ‘up-and-down’ method. Thirty min after the clonidine infusion anaesthesia was induced with etomidate, 0.25 mg kg−1. Skin incision was made after stable end-tidal isoflurane concentrations had been maintained for at least 15 min. Clonidine caused significant decreases in the spectral edge (95%) and median power frequency of the electroencephalogram and in the bispectral index. The minimal alveolar concentration of isoflurane decreased in a dose-dependent manner from 1.32% (95% CI, 1.28%–1.36%) in the control group to 1.03% (0.9%–1.18%) in patients given clonidine 6 μg kg−1. Clonidine 4 and 6 μg kg−1 was associated with a moderate reduction in heart rate and arterial systolic blood pressure. We recommend the use of clonidine intravenously as an adjunct to general anaesthesia in a dose of 4 μg kg−1 given 15 min before induction of anaesthesia.

Keywords

alpha2-adrenoceptor agonistclonidineintravenousminimal alveolar concentrationiso-fluraneEEG
Type
Original Article
Information
European Journal of Anaesthesiology , Volume 17 , Issue 2 , February 2000 , pp. 105 - 110
Copyright
2000 European Society of Anaesthesiology

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