Anesthesia Awareness and the Bispectral Index

To the Editor: Avidan et al. (March 13 issue) 1 confirm that bispectral index (BIS)–guided care achieves a 0.2% incidence of awareness during anesthesia in high-risk patients, as previously reported, 2 but further conclusions and recommendations are not supported. Despite the investigators' original hypothesis “that the incidence of awareness [with an end-tidal protocol] will be equivalent to or lower” than that with a BIS-guided protocol, 3 the sample-size calculation erroneously assumed no treatment effect for the anesthetic protocol (Table 1). Consequently, this study had an 80% probability of missing a 50% difference in the relative efficacy of the two interventions. 4 Unexplained gaps in . . .