ORAL CLONIDINE PREMEDICATION REDUCES MINIMUM ALVEOLAR CONCENTRATION OF SEVOFLURANE FOR TRACHEAL INTUBATION IN CHILDREN

Background: Sevoflurane is a useful anesthetic for inhalational induct ion in children because of its low solubility in blood and relatively nonpungent odor. Clonidine has sedative and anxiolytic properties and reduces the requirement for inhalation agents. Nitrous oxide (N2O) als o decreases the requirement of inhaled anesthetics, but the effect is variable; The minimum alveolar concentration for tracheal intubation ( MAC(TI)) of sevoflurane was assessed with and without N2O and clonidin e premedication. Methods: Seventy-two patients, aged 3-11 yr, were ass igned to one of sin groups (n = 12 each). They received one of three p reanesthetic medications (two groups for each premedication): placebo (control), 2 mu g/kg oral clonidine or 4 mu g/kg oral clonidine. In on e: group of each premedication, anesthesia Tvas induced with sevoflura ne in oxygen; in the other group, anesthesia was induced with sevoflur ane in tile presence of 60% N2O. Each concentration of sevoflurane at which tracheal intubation was attempted was predetermined according to Dixon's up-and-down method and held constant for at Least 20 min befo re the trial. Results: The MAC(TI) of sevoflurane in the absence of N2 O (mean +/- SEM) was 3.2 +/- 0.2%, 2.5 +/- 0.1%, and 1.9 +/- 0.2% in t he control, 2-mu g/kg clonidine, and 4-mu g/kg clonidine groups, respe ctively Nitrous oxide (60%) decreased the MAC(TI) of sevoflurane by 26 %, 24%, and 27% in the control, 2-mu g/kg clonidine, and 4-mu g/kg clo nidine groups. Conclusions: Oral clonidine premedication decreased the MAC(TI) of sevoflurane. Nitrous oxide also decreased the MAC(TI). The combination of clonidine and N2O lessened the MAC(TI) of sevoflurane more than did either drug alone.