Integrating BIS and cerebral oximetry in anesthesia: a narrative review on advanced monitoring for cardiac surgery

Abstract

Monitoring anesthetic depth and cerebral oxygenation is particularly important in cardiac anesthesia, where patients are at increased risk of neurological complications and hemodynamic instability. Conventional monitoring approaches based primarily on vital signs and clinical assessment may lack sensitivity for detecting subtle cerebral hypoxia or inadequate anesthetic depth during complex procedures. This narrative review employed a structured literature search of PubMed, Scopus, and Web of Science to identify relevant clinical studies, reviews, and case reports evaluating the use of Bispectral Index (BIS) monitoring and near-infrared spectroscopy (NIRS)–based cerebral oximetry in cardiac anesthesia. The review focuses on the complementary physiological information provided by BIS, which estimates anesthetic depth from electroencephalographic activity, and cerebral oximetry, which enables continuous assessment of regional cerebral oxygenation. Evidence from randomized trials and observational studies suggests that BIS-guided anesthesia is associated with a reduced incidence of intraoperative awareness, shorter extubation times, and decreased intensive care unit length of stay, while defined cerebral oximetry thresholds are consistently linked to postoperative cognitive dysfunction and adverse neurological outcomes. When used together, BIS and NIRS may facilitate earlier recognition of inadequate sedation, cerebral hypoperfusion, and global physiological compromise during cardiopulmonary bypass, with case reports highlighting critical scenarios such as “triple low” states and refractory cerebral desaturation. The review also proposes a conceptual framework and an interim standard operating procedure to guide integrated use of these modalities in clinical practice. Important limitations are discussed, including interindividual pharmacologic variability, sensor-related artifacts, and patient-specific heterogeneity, which contribute to variability in signal interpretation. Emerging directions such as adaptive algorithms, multimodal neuromonitoring platforms, and wireless technologies integrated into Enhanced Recovery After Surgery pathways are also considered. Overall, although BIS and cerebral oximetry each provide incomplete information when applied in isolation, their combined use offers a potentially synergistic neuromonitoring strategy in cardiac anesthesia. The current evidence base, however, remains heterogeneous, underscoring the need for large-scale, methodologically robust studies to clarify outcome benefits and inform standardized implementation.