Bispectral Index Monitoring in Anesthesiology: A Narrative Review

Introduction: Accurate assessment of anesthetic depth is crucial for patient safety and optimal drug administration. The Bispectral Index (BIS), an EEG-derived quantitative measure, has become widely used to monitor hypnosis in various anesthetic contexts. Despite its popularity, BIS interpretation faces challenges from physiological variability, patient-specific factors, and technical limitations. Methods: This narrative review synthesized evidence from PubMed searches restricted to the last 10 years, including randomized controlled trials, systematic reviews, and observational studies evaluating BIS monitoring. Articles covering technical aspects, clinical applications, patient-group specific performance, limitations, physiological correlations, and outcomes were prioritized. Thematic synthesis was used rather than meta-analysis. Results: BIS effectively guides anesthetic titration, reducing intraoperative awareness and anesthetic consumption across adult and pediatric populations. Challenges include variability due to age-related EEG differences, EMG interference, and anesthetic agent-specific EEG effects. Complementary indices like response entropy and machine learning models enhance BIS reliability. Closed-loop anesthesia delivery guided by BIS shows promise in improving administration precision. Optimal BIS ranges support improved hemodynamics and reduce postoperative morbidity and mortality risks. Conclusions: BIS remains a valuable clinical tool for monitoring anesthetic depth when interpreted with awareness of its limitations. Advances in AI, multimodal monitoring, and personalization will likely improve BIS utility. Continued research is essential to optimize anesthesia management and patient outcomes through enhanced brain monitoring technologies.