The effect of bispectral index monitoring on end-tidal gas concentration and recovery duration after outpatient anesthesia

We performed this study to determine whether instituting monitoring of bisp ectral index (BIS) throughout an entire operating room would affect end-tid al gas concentration (as a surrogate for anesthetic use) or speed of recove ry after outpatient surgery. Primary caregivers (n = 69) were randomly assi gned to a BIS or non-BIS Control group with cross-over at 1-mo intervals fo r 7 mo. Data were obtained in all outpatients except for those having head- and-neck surgery. Mean end-tidal gas concentration and total recovery durat ion were compared by unpaired t-test. Overall, 469 patients (80%) received propofol for induction and sevoflurane for maintenance. This homogeneous gr oup was selected for statistical analysis. Mean end-tidal sevoflurane conce ntration was 13% less in the BIS group (BIS, 1.23%; Control, 1.41%; P < 0.0 001); differences were most evident when anesthesia was administered by fir st-year trainees. Mean BIS values were 47 in the BIS-Monitored group. Total recovery was 19 min less with BIS monitoring in men (BIS group, 147 min; C ontrols, 166 min; P = 0.035), but not different in women. We conclude that routine application of BIS monitoring is associated with a modest reduction in end-tidal sevoflurane concentration. In men, this may correlate with a similar reduction (11%) in recovery duration.