Correlation Of Bispectral Index With End-tidalsevoflurane Concentration During The Maintenance Phase Of Anesthesia

Objective:To observe the effect of sevoflurane on bispectral index and to evaluate the usefulness of bispectral index for momitoring thedepth of sevoflurane anesthesia in adults undergoing elective urologysurgery.Methods:Thirty-five adults classified as ASA physical status I~II,aged 22 to 77 yr,who undergoing elective urology surgery were enrolled in the study.They were induced with i.v.propofol 1.5mg/kg,fentanyl 4μg/kg and scoline 1~1.5mg/kg,and thenthe LMA were intubated.Anaesthesia was maintained with sevoflurane and acis-atracurium.End-tidalconcentration of sevoflurane were maintained at 0.6 MAC,0.8 MAC,1.0MAC and 1.2 MAC for at least 10 min respectively.The changes of BIS,mean arterial blood pressure(MAP)and heart rate(HR)were recorded simultaneously at each timepoints.Results:During anesthesia of sevoflurane,BIS decreased significantly compared with that at preanesthesia(P<0.05)with increasing end-tidal sevoflurane concentration from 0.6MAC to 1.2MAC.The coeficient of product-moment correlation(r)of the BIS with the end-tidalsevofluraneconcentrationwere-0.643(P<0.05).Conclusions:During the maintenance phase of sevoflurane-based general anesthesia,considering wide interindividual variability,BIS frequently correlatedpoorly with anesthetic concentration and was often insensitiveto changes in anesthetic concentration.It is controversial to use BIS monitoring during inhaled anesthsia.