The Comparability of Bispectral Index and State Entropy Index During Maintenance of Sufentanil-Sevoflurane-Nitrous Oxide Anesthesia

BACKGROUND: Manufacturers recommend maintaining Bispectral (BIS) or Spectral Entropy (State Entropy, SE) indexes between 40 and 60 during the maintenance of anesthesia. We compared these indexes during this period. METHODS: Data were obtained from 58 patients receiving sufentanil-sevoflurane-nitrous oxide anesthesia. The anesthesiologist was blinded to BIS and SE. Artifact-free concurrent BIS and SE values (7792 pairs), automatically recorded at 1-min intervals, were compared using Bland-Altman analysis, Kappa coefficient for agreement and crude proportion of agreement. The occurrence of errors of judgment (Type 1 defined as one parameter 60, or Type 2 defined as BIS and SE values on different sides of a threshold [40 or 60]) was also counted. RESULTS: Bias was -2 with limits of agreement of -18 and 9. Kappa BIS/SE obtained from all patients was 0.537 ± 0.147; crude agreement >0.80 was observed in 45% of patients. Type 1 number of errors of judgment corresponded to two instances. Median and interquartile values of Type 2 number of errors of judgment were 4.5 [3.0-6.0] when considering a difference between BIS and SE more than 5. CONCLUSION: Although limits of agreement between BIS and SE were large, Kappa value moderate, and crude agreement