Assessing the depth of dexmedetomidine-induced sedation with electroencephalogram (EEG)-based spectral entropy

Background: Adequate sedation of critically ill patients improves the outcome of intensive care. Maintaining an optimal level of sedation in the intensive care unit (ICU) is difficult because of a lack of appropriate monitoring methods to guide drug dosing. Dexmedetomidine, a selective α2‐adrenoceptor agonist, has recently been introduced for the sedation of ICU patients. This study investigated the utility of electroencephalogram (EEG)‐based spectral entropy monitoring (with M‐ENTROPY™, GE Healthcare, Helsinki, Finland) for the assessment of dexmedetomidine‐induced sedation. Methods: Eleven healthy, non‐smoking men, aged 23.9 ± 2.5 years (mean ± standard deviation), were recruited. Spectral entropy was recorded before and during low (0.5 ng/ml) and high (5 ng/ml) plasma concentrations of dexmedetomidine. At the end of the infusion, subjects were awakened by verbal command and light shaking. Results: Spectral entropy decreased from 84 ± 5 to 66 ± 16 (P= 0.029) during low dexmedetomidine levels and from 84 ± 5 to 20 ± 12 (P < 0.001) during high dexmedetomidine levels. Transitions during loss and regaining of consciousness were analysed separately. Entropy decreased from 76 ± 8 before to 43 ± 10 (P < 0.001) after loss of consciousness, and increased from 14 ± 4 to 63 ± 13 (P < 0.001) on regaining of consciousness. These changes were consistent across all subjects. Prediction probability and sensitivity values indicated a high predictive performance of the method. Conclusion: The depth of dexmedetomidine‐induced sedation can be monitored with EEG‐based spectral entropy. These results should be confirmed in a clinical setting.