BIS versus skin conductance for assessment of depth of sedation induced by propofol target-controlled infusion

Abstract

Objective To compare the accuracy of BIS and skin conductance (SC) for assessment of the depth of sedation induced by target-controlled infusion (TCI) of propofol. Methods Thirty ASA Ⅰ orⅡpatients aged 21-56 yr weighing 52-85 kg undergoing orthopedic operation on the lower limb under epidural anesthesia were enrolled in this study.After the onset of epidural anesthesia, TCI of propofol was started at an initial target plasma concentration (Cp) of 0.8 μg/ml. Th Cp was increased by 0.5-0.8 μg/ml every 3 min until OAA/S score=1. OAA/S score, BIS and SC values were recorded, SC change value (△SC) was calculated. Spearman rank-order correlation, receiver operating characteristic curve (area under curve was calculated) and logistic regression were used to analyze the relationship of OAA/S score to BIS and △SC.Results BIS and △SC were significantly correlated with OAA/S scores (r were 0.920 and-0.859 respectively). The AUC of △SC (0.919, 0.946) was significantly better correlated with OAA/S score (5→4, 4→3) than that of BIS (0.761, 0.507), while BIS was better correlated (0.781, 0.959) with OAA/S score (3→2, 2→1) than ASC (0.577, 0.630). Logistic regression correctly predicted loss of consciousness. The accuracy of prediction was 93% for BIS and 82% for △SC. Conclusion The accuracy of SC for assessment of the depth of sedation induced by propofol TCI ishigher than that of BIS before loss of consciousness,while lower than that of BIS after loss of consciousness. BIS is more accurate in monitoring the loss of consciousness. Key words: Electroencephalography; Galvanic skin response; Propofol; Conscious sedation; Drug delivery systems