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Objective:To assess the accuracy of the application of Bispectral index in monitoring sedation with dexmedetomidine.Methods:We selected sixty ASAⅠandⅡpatients under combined spinal-epidural anesthesia using knee arthroscopy in the study. The patients were randomly divided into three groups:group D(n=20): dexmedetomidine; group P(n=20):propofol; and group M(n=20): midazolam. We gave the combined spinal-epidural anesthesia to the patients and adjusted the anesthesia level to T12～S5. We began to administer the sedative drugs on the 5 minutes before incision. Group D: The first step contained loading dose and maintenance dose. The loading dose of dexmedetomidine was administered for 15 min(1 ug/kg), and the maintenance dose of the first was 0.05ug·kg-1·h1, the second step and the third step was followed by continuous infusion(1.0μg·kg-1·h-1, 1.5μg·kg-1·h-1), each step was maintained for 40min. Group P:propofol was administrated in increasing steps to target effect-site concentrations of 1,2, and 4ug/ml. Each concentration was maintained for 40min. Group M:midazolam was administrated in continuous increasing step infusion(0.05mg·kg-1·h-1,0.1mg·kg-1·h-1,0.2mg·kg-1·h-1). Among 120min, each concentration was maintained for 40min. BIS, HR, BP, SPO2 and Observers’s Assessment of Alertness-Sedation were measured in each patient every 5 min by the same person who didn’t know the sedative drugs. BIS was recorded before each OAA/S evaluation. Then the anterograde amnesia was carried after the test of OAA/S. The adverse reaction were recorded.Results:1. At OAA/S scores of 5,4,3,2, and 1, BIS values during dexmedetomidine sedation were 93.0(95.0～82.0),93.0(95.0～82.0), 79.0(83.5～75.5),60.0(64.0～58.0),48.0(50.0～47.5),35.0(38.0～31.5) respectively. BIS values during propofol sedation were 94.0(95.8～92.0), 83.0(86.0～82.0),72.0(78.0～67.3),63.0(68.1～57.5),45.0(49.2～38.0) respectively. BIS values during midazolam sedation were 94.5(96.8～93.3),86(88.0～84.0),79.5(83.5～78),75.0(76～73),64.5(66.3～60) respectively.2. The BIS of the three groups positively correlated with the OAA/S, but poorer in the group of dexmedetomidine than the other two. The Pk values for BIS were high in all groups, but poorer in the group of dexmedetomidine than the other two.3. The calculated cutoff BIS values for OAA/S scores of≤2 were 51 (sensitivity of 86.6%, specificity of 90.9%) for dexmedetomidine and 69 (sensitivity of 89%, specificity of 95%) for propofol and 76(sensitivity of 87.2%, specificity of 91%) for midazolam.Conclusions:BIS can be an effective monitor of the sedation with dexmedetomidine, but less accuracy than with propofol and midazolam.
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