Oral clonidine premedication reduces minimum alveolar concentration of sevoflurane for laryngeal mask airway insertion in children

BACKGROUNDS: Sevoflurane is widely employed for inhalational induction in children. Clonidine deepens volatile anesthetics and reduces several types of MAC of sevoflurane. Laryngeal mask airway is a useful device for pediatric anesthesia. The aim of the current study was to determine whether oral clonidine premedication can reduce MAC of sevoflurane for an LMA insertion in children. METHODS: Fifty-six ASA physical status I patients (3-11 years) scheduled for general anesthesia were randomly divided into two groups of 28 patients each. One group (clonidine group) received clonidine 4 microg x kg(-1) approximately 100 min before anesthesia, and the other (control) group did not. Anesthesia was induced with sevoflurane. Each concentration of sevoflurane, at which an LMA insertion was attempted, was predetermined according to the modification of Dixon's up-and-down method with 0.25% as a step size and held constant for at least 20 min before the trial. All responses ('movement' or 'no movement') to an LMA insertion were assessed. RESULTS: Minimum alveolar concentration values of sevoflurane for an LMA insertion were lower in the clonidine group (1.31% +/- 0.18% [mean +/- sd]) than in the control group (2.00% +/- 0.16%). Logistic regression analysis revealed that sevoflurane EC95 values were 1.79% and 2.49% in the clonidine and control groups, respectively. CONCLUSIONS: Oral clonidine premedication reduced the MAC (EC50) and EC95 values of sevoflurane for LMA insertion by 38% and 28%, respectively.