CORRELATION OF BISPECTRAL INDEX (BIS) WITH END-TIDAL SEVOFLURANE CONCENTRATIONS IN INFANTS AND CHILDREN

Abstract

S396 Introduction: BIS has been used to determine the hypnotic effects of several intravenous and volatile agents, including sevoflurane, but data have not been collected in children. We maintained various steady-state end-tidal concentrations of sevoflurane in N2 O and documented the corresponding BIS in infants (0 - 2 yr) and children (2 - 12 yr). Methods: Twenty-two unpremedicated patients undergoing elective surgery were enrolled in this institutionally-approved protocol. Anesthesia was induced with sevoflurane in 60% N2 O/O2 with or without propofol. BIS measurements were delayed at least 20 min following propofol. Opioids and muscle relaxants were given as clinically indicated. BIS was recorded on an ASPECT Medical Systems Model A1050 EEG monitor. End-tidal sevoflurane concentrations were measured with a Datex Ultima Capnomac[registered sign] or Ohmeda RGM 5250[registered sign] monitor and maintained within 0.1% of these targets: 4, 3, 2, 1.5, 1, 0.5%. BIS was stable for at least 5 min at each concentration before it was recorded. Data for each group were fit to an inhibitory sigmoid Emax model (SlideWrite Plus[copyright sign]. Results: Table 1 shows the demographics of the 2 groups. BIS fell with increasing concentrations of sevoflurane (see Figure 1). Overall responses and awake values (not shown) did not appear to differ from those reported in adults. The sevoflurane concentration for a half-maximal response (95% C.I.) was significantly different between groups: 1.55% (1.40 - 1.70) for infants vs. 1.25% (1.12 - 1.37) for children.Table 1Figure 1Conclusion: BIS correlates with sevoflurane concentration in children and infants. This is similar to the correlation in adults. The concentration-response difference between infants and children is consistent with data showing that MAC (minimum alveolar concentration) is higher in children less than one year of age. [1,2]