BIS Monitoring on Intraoperative Awareness: A Meta-analysis

Intraoperative awareness is a very serious complication of general anesthesia. Several studies have evaluated the potential association between bispectral index (BIS) and intraoperative awareness, however, the results obtained were controversial. Therefore, we performed a meta-analysis to further assess the association between the BIS monitoring and the incidence of intraoperative awareness. A comprehensive search was conducted to identify all eligible studies from the online literature databases published prior to Feb. 2017. A total of five studies with 17 432 cases and 16 749 controls were included. An odds ratio (OR) and a 95% confidence interval (CI) were calculated to examine the strength of the association. The results showed that in the overall analysis, the association between the BIS monitoring and the incidence of intraoperative awareness was not significant (OR=0.58, 95% CI= 0.22–1.58, P=0.29). A stratified analysis by comparing different anesthesia methods revealed that BIS monitoring group showed a lower incidence of intraoperative awareness in patients with intravenous anesthesia when compared with non-BIS monitoring group (OR=0.20, 95% CI=0.08–0.49, P=0.0004), whereas there was no statistically significant difference in the incidence of intraoperative awareness between BIS and non-BIS monitoring groups in patients with inhalation anesthesia (OR=1.13, 95% CI=0.56-2.26, P=0.73). In conclusion, our meta-analysis showed that BIS monitoring had no appreciable advantage in the reduction of the intraoperative awareness incidence in inhalation anesthesia, while showed a remarkable superiority in intravenous anesthesia.