The Differences in the Bispectral Index Between infants and Children During Emergence from Anesthesia After Circumcision Surgery

The bispectral index (BIS) correlates with consciousness during adult anesthesia. In this prospective, blinded study of children (n = 24) and infants (n = 25) undergoing elective circumcision, we evaluated BIS and consciousness level during emergence from anesthesia. Anesthesia was maintained with sevoflurane, and a penile nerve block was performed in each patient before surgical stimulation. At the completion of surgery, the sevoflurane was decreased stepwise from 0.9% in increments of 0.2%, and arousal was tested with a uniform auditory stimulus given after a steady state of end-tidal sevoflurane concentration was achieved at each step. The BIS increased significantly as the sevoflurane concentrations decreased in children (0.9%, 62.5 ± 8.1; 0.7%, 70.8 ± 7.4; and 0.5%, 74.1 ± 7.1;P < 0.001 for 0.7% and 0.5% compared with 0.9%), but a similar relationship was not demonstrated in infants. The BIS values at 0.7% and 0.5% sevoflurane were significantly higher in children than infants (P < 0.02 and P < 0.002, respectively). In both children and infants, the BIS increased significantly from pre- to postarousal (children, 73.5 ± 7 to 83.1 ± 12, P = 0.01; infants, 67.8 ± 10 to 85.6 ± 13.6, P < 0.001). The BIS at which arousal was possible with the stimulus tended to be higher in children than in infants (P = 0.06).