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The awakening concentration of sevoflurane in children
S Kihara1, S Inomata, Y Yaguchi
1Department of Anesthesiology and Clinical Pharmacology, University of Tsukuba, Ibaraki, Japan. sin-ki@fa2.so-net.ne.jp
Insights
Clonidine premedication significantly reduced the sevoflurane awakening concentration in children. A 2 microg/kg dose of oral clonidine lowered the minimum alveolar concentration for awakening, but higher doses showed no additional benefit.
Area of Science:
- Anesthesiology
- Pediatric Anesthesia
- Pharmacology
Background:
- Sevoflurane is a common anesthetic induction agent.
- Understanding its awakening concentration (MAC-awake) is crucial for pediatric anesthesia.
- Clonidine is used for its sedative and analgesic properties.
Purpose of the Study:
- To determine the MAC-awake of sevoflurane in children.
- To investigate the effect of two different oral clonidine doses (2 and 4 microg/kg) on sevoflurane's MAC-awake.
- To assess potential dose-response relationships of clonidine on anesthetic emergence.
Main Methods:
- Children (2-10 years, ASA I) were randomized into placebo, clonidine 2 microg/kg, or clonidine 4 microg/kg groups.
- Clonidine or placebo was administered orally 100 minutes before anesthesia induction.
- Anesthesia was induced and maintained with sevoflurane; MAC-awake was determined by stepwise reduction of end-tidal sevoflurane with a verbal command stimulus.
Main Results:
- The MAC-awake of sevoflurane alone was 0.78% ± 0.24%.
- Premedication with 2 microg/kg clonidine reduced MAC-awake to 0.36% ± 0.09% (P < 0.0001).
- Premedication with 4 microg/kg clonidine also resulted in a MAC-awake of 0.36% ± 0.16% (P < 0.0001), showing no further reduction compared to the lower dose.
Conclusions:
- The MAC-awake of sevoflurane in unpremedicated children is 0.78%.
- Oral clonidine at 2 microg/kg effectively reduces sevoflurane MAC-awake in children.
- A higher dose of 4 microg/kg clonidine did not provide additional reduction in MAC-awake, suggesting a possible plateau effect.
Unlabelled:
Sevoflurane is frequently used as a rapidly acting drug for the induction of anesthesia. We investigated the awakening concentration (MAC-awake) of sevoflurane in ASA physical status I children (age range 2-10 yr). We also investigated the effects of two different doses of clonidine (2 and 4 microg/kg) on the MAC-awake of sevoflurane. Subjects were randomly divided into three groups and received placebo (n = 24), clonidine 2 microg/kg (n = 17), or clonidine 4 microg/kg (n = 22) orally, 100 min before the induction of anesthesia. Sedation scores were estimated, by using a five-point scale, after entry into the operating room, and anesthesia was induced and maintained with sevoflurane in oxygen and balanced nitrogen, without an additional anesthetic. After surgery, end-tidal sevoflurane was decreased stepwise by 0.2% at 15-min intervals, a standardized verbal command was played to the patients, and the MAC-awake was determined. The MAC-awake of sevoflurane alone was 0. 78% +/- 0.24% (mean +/- SD), which decreased to 0.36% +/- 0.09% and 0.36% +/- 0.16% (both P <0.0001, compared with the control group) after premedication with the small and large doses of clonidine, respectively. The lack of any dose-response relationship might be explained by a plateau effect.
Implications:
The awakening concentration of sevoflurane in unpremedicated children was 0.78%. Oral clonidine premedication at a dose of 2 microg/kg reduced the awakening concentration to 0.36%. However, an additional decrease in this value was not observed after the administration of the larger dose of clonidine premedication (4 microg/kg).