Monitoring depth of sedation: Evaluating the agreement between the Bispectral Index, qCON and the Entropy Module's State Entropy during flexible bronchoscopy

BACKGROUND: We investigated the correlation and agreement of three depth of anesthesia indices, Bispectral Index (BIS), qCON and state entropy (SE) during propofol sedation, because there is extensive literature that deals with the comparability of these indices during general anesthesia, but not during sedation. METHODS: We recorded electroencephalogram (EEG) and SEtrend data, using the Entropy Module from 21 patients who underwent elective bronchoscopy with target-controlled infusion of propofol. EEGdata were replayed to BISand qCON with an EEGplayer. We calculated the Spearman correlation to evaluate similarities in index trend behavior and estimated the general index agreement of displaying the same anesthetic level, i.e., wakefulness, sedation and anesthesia. We used coughing episodes and the bronchoscope placement to investigate the index for possible arousal reactions. RESULTS: We found a high to very high correlation of the indices' trend during the procedure. Furthermore, qCON was significantly lower than BIS and SE. All indices increased significantly after bronchoscope placement and coughing. The agreement of BIS/SEwas 68% and around 50% for BIS/qCON and qCON/SE. The median duration of disagreement by >10 points was 39 s for BIS/SEand around 75 s for qCON with BISand SE. CONCLUSIONS: The results indicate a high probability of similar index performance between SE, BISand qCON with the caveat of a different index scaling for qCON. These results can help the user of these monitoring devices to translate findings from one index to the other.