Comparative evaluation of the bispectral index (BIS) and BISpro during propofol anaesthesia

OBJECTIVE: To compare the accuracy, correlation and agreement between the bispectral index (BIS) and BISpro during propofol anaesthesia. METHODS: The BIS, BISpro, heart rate, target-concentration of propofol and Observer’s Assessment of Alertness and Sedation (OAA/S) score were recorded every 30 s in female patients scheduled for hysteroscopic surgery. Propofol anaesthesia was induced by an initial target-controlled concentration (1.0 μg/ml) followed by a stepwise increase (0.5 μg/ml) until the patient was unresponsive. Spearman’s correlation coefficient and prediction probability were calculated for the association between sedation levels and the above parameters. The ability of investigated parameters to distinguish between OAA/S scores was analysed. Bland–Altman analysis was used to compare the agreement between BIS and BISpro. The BIS and BISpro cut-off values for lost response were also determined. RESULTS: Out of 30 patients in total, a high correlation was found between BIS and BISpro, and both correlated well with OAA/S score. Only BIS was able to distinguish all investigated OAA/S states accurately, but the ability to predict OAA/S score 5 to loss of response was comparable between BIS and BISpro. The calculated cut-off values were 68 for BIS and 70 for BISpro. CONCLUSION: BISpro and BIS are reliable monitors of general anaesthesia during sedation. Trial registration number: Chinese Clinical Trial Registry (URL: www.chictr.org.cn): ChiCTR1900024037 (retrospectively registered).