Correlation of bispectral index with end-tidal sevoflurane concentration and age in infants and children

Abstract

BACKGROUND: The bispectral index (BIS) has been evaluated as a tool for measuring depth of anaesthesia, but the use of BIS in a paediatric population is still controversial. This study was designed to evaluate the correlation of BIS with end-tidal sevoflurane concentration and age in infants and children. METHODS: Eighty-one patients undergoing elective urology surgery were allocated into three age groups; 6 months to 2 yr (n=28), 3-7 yr (n=33), and 8-12 yr (n=20). Sevoflurane was administered to achieve steady-state end-tidal sevoflurane concentrations (ET(sevo)) of 2.0, 3.0, and 4.0%; these were achieved consecutively either from the lowest or from the highest concentration. The BIS (version XP) was monitored continuously. RESULTS: In all three groups, BIS decreased significantly when ET(sevo) increased from 2.0 to 3.0% but there was a paradoxical increase in BIS values when ET(sevo) increased from 3.0 to 4.0%. The non-linear regression analysis showed a significant correlation between BIS and age at each ET(sevo). The younger patients showed the higher BIS values. CONCLUSIONS: In children aged 6 months to 12 yr, the BIS increased paradoxically as ET(sevo) increased from 3.0 to 4.0%. BIS values showed a wide variation in the same ET(sevo) and the age itself was considered to be a factor affecting the BIS values.