The bispectral index (BIS) was developed for adults, and the influence of neuronal and physiologic brain maturation on BIS in pediatric patients is unknown. The aim of this study was to evaluate BIS during anesthesia, using the same sevoflurane with respect to age in young children. Methods: Forty-two pediatric patients, aged 1-7 years, were enrolled in this study. Without premedication, anesthesia was induced with atropine, thiopental, and rocuronium and maintained with 2.0-2.5% sevoflurane

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... 50% N2O-50% O2. After induction, a pediatric BIS sensor was applied and monitored throughout the maintenance of and emergence from anesthesia. Results: BIS was analyzed in different age groups; 1-2 yr (n = 14), 3-4 yr (n = 13), 5-7 yr (n = 15). Operation and anesthesia times were similar forthe three age groups. Mean BIS values from ten minutes after skin incision to just before sevoflurane cessation (BISmean) were 67.0 ± 6.2 for 1-2 yr, 50.5 ± 9.4 for 3-4 yr, and 39.8 ± 6.9 for 5-7 yr, and these values were significantly different for the three age groups. No significant differences were observed for extubation times, or times to a BIS value of 70 or 90 during anesthesia recovery. Conclusions: When monitoring BIS in children aged 1-7 yr during anesthesia with sevoflurane, the BIS trend rather than the absolute value is more important and the BIS data, especially in children under 3 years of age, should be interpreted cautiously.