BACKGROUND: The bispectral index (BIS) has been used as a monitor measuring hypnotic level of anesthesia or sedation. Recently EEG-entropy (M-Entropy™, S/5™ Entropy Module) has been provided and started to use domestically. This study was designed to compare the measured values between EEG-entropy and BIS monitor on general anesthesia and sedation.

METHODS: Thirty patients undergoing total hysterectomy were anesthetized with propofol target controlled infusion (TCI), fentanyl, rocuronium and BIS, RE (response entropy), SE (state entropy), and hemodynamic variables were measured at the effect site concentration of 1.5-10.0 µg/ml (P15-P100). On the other hand, fifteen patients undergoing breast biopsy were sedated with propfol TCI and BIS, RE and SE were measured at 0.9-2.3 µg/ml (P09-P23).

RESULTS: During general anesthesia, SE values were significantly lower than BIS or RE at baseline. But RE alone at P15, RE and SE at P20 were significantly higher than BIS. During sedation, SE values were significantly lower than BIS or RE at baseline-P09 and significantly lower than RE alone at P10-P15, and RE were significantly higher than BIS at P13-P20. After P21, RE and SE values fell abruptly and approached to BIS.

CONCLUSIONS: EEG-entropy reflected hypnotic level well equal to BIS during general anesthesia. However, EEG-entropy did less reflected the hypnotic level than BIS during sedation.