[Application of the bispectral index monitor in mechanical ventilation in patients under sedation in the intensive care unit].

OBJECTIVE: To evaluate bispectral index (BIS) technology in post-operative patients under sedation undergoing mechanical ventilation according to Ramsay sedation scales in intensive care unit (ICU). METHODS: Thirty post-operative patients on mechanical ventilation were sedated with midazolam or propofol intravenously. All patients were evaluated for their levels of sedation by using BIS and the Ramsay scale simultaneously every 5 minutes with blind method. The total differences of median BIS in each sedation scale were compared. The BIS measurements and the corresponding Ramsay scale measurements were selected for analyzing the correlations. The sensitivity of BIS and Youden index were calculated, and the sensitivity and specificity of BIS were identified. RESULTS: The median BIS corresponding to each Ramsay scale decreased significantly along with the increasing of sedation depth. There were significant differences of median BIS in each Ramsay sedation scale (P<0.001). BIS was negatively correlated with Ramsay scale, and the r value was -0.794 (P<0.01). When the patient was optimally sedated (Ramsay scale 2-5 scores), the corresponding median BIS 95% confident interval (CI) were 61-84. The sensitivity and Youden index of BIS value with optimal or under sedation were the highest when BIS=81. The 95% CI of median BIS were 48-58 when Ramsay scale was 6 scores. CONCLUSION: BIS measurements evaluated in clinically relevant ranges compare favorably with Ramsay scale. BIS may be best used to identify and prevent over or under sedation of mechanical ventilated patients in the ICU.