Bispectral index (BIS) in infants anesthetized with sevoflurane in nitrous oxide and oxygen

BACKGROUND: The bispectral index (BIS) has been shown to be useful in monitoring a degree of hypnosis in anesthetized adults. Although several studies have been performed to evaluate BIS in pediatric patients, it is unclear whether BIS monitor can be applied to infants. This study was designed to evaluate if the BIS monitor can be used in infants as a measure to monitor a degree of hypnosis. METHODS: Forty-three infants were divided into two age groups according to their age: group A (3-6 months; n = 31) and B (7-12 months; n = 12). And the patients in the younger group were randomly allocated to one of two groups, A (+) (premedicated with oral midazolam 0.5 mg.kg-1; n = 19) and A (-) (without premedication; n = 12). BIS values and other parameters were recorded at a steady state of end-tidal sevoflurane concentration (2.5, 2, and 1.5%) and immediately before extubation. RESULTS: At each concentration of sevoflurane and extubation, the BIS values were lower in group A (+) than in group B (P or = 7 months old infants. BIS values should be interpreted cautiously in infants younger than 6 months.