BIS Versus End-tidal Anaesthetic Gas Concentration-guided General Anaesthesia for Prevention of Intraoperative Awareness in Elective Surgery: A Randomised Controlled Trial

Background Awareness during general anaesthesia (GA) is a rare but serious complication, affecting 0.15%–0.2% of patients, with potential psychological consequences such as post-traumatic stress disorder (PTSD). Bispectral index (BIS) monitoring, which uses electroencephalography (EEG)-derived metrics to assess anaesthesia depth, has shown promise in reducing intraoperative awareness, though its universal adoption remains limited due to mixed evidence. Purpose This study aimed to compare BIS-guided and end-tidal anaesthetic gas concentration (ETAG)-guided techniques in a randomised controlled trial conducted in India, addressing gaps in existing literature, particularly among Asian populations. Methods A total of 674 patients, aged 18–65 years, undergoing elective surgeries were randomised into two groups: BIS ( n = 341) and ETAG ( n = 333). The assessment of intraoperative awareness in both study groups was conducted using two distinct methods. Two independent interviewers, both blinded to the study conditions, carried out these assessments. The first method involved the modified Brice interview, while the second employed the Michigan Awareness Classification Instrument. Results Awareness incidence was 0.58% in the BIS group and 0.90% in the ETAG group ( p = .63), with no statistically significant differences. Secondary outcomes, including time to eye opening, extubation, hospital stay duration and incidence of postoperative nausea and vomiting (PONV), were also comparable. Both methods provided equivalent anaesthetic depth and haemodynamic stability. Conclusion This randomised trial found that neither BIS nor minimum alveolar concentration (MAC) demonstrated superiority in terms of intraoperative awareness. Future research should focus on high-risk populations, explore stringent BIS targets (e.g., BIS <50) and explore the cost-effectiveness of these monitoring techniques in various clinical settings.