Reduced neural activity during volatile anesthesia compared to TIVA: evidence from a novel EEG signal processing analysis

Abstract

Background Post-operative cognitive dysfunction/decline is a well-known phenomenon and of crucial importance, especially in the elderly, emphasizing the significance of selecting the proper anesthetics. General anesthesia can be accomplished by inhalation-based (volatile) or total intravenous anesthesia (TIVA). While their effects on post-operative symptoms have been investigated, little is known about their influence on brain functionalities during the surgery itself. Objective To assess differences in brain activity between volatile and TIVA anesthetics during surgery. Methods Seventeen patients who were electively scheduled for laparoscopic cholecystectomy in Galilee Medical Center, Nahariya, gave written informed consent to participate in the study and were randomly divided to receive either volatile anesthesia (n = 9), or TIVA (n = 8). The level of anesthesia was kept equal in both groups. A single bipolar EEG electrode (Aurora by Neurosteer®) was placed on each participant’s forehead. The electrode presented real-time activity and collected participants’ data during the surgery. The dependent variables included frequency bands (delta, theta, alpha, and beta), and three features (VC9, ST4, and A0) previously extracted with the Aurora device and provided by Neurosteer®. Results All surgeries were uneventful, and all patients showed bispectral index (BIS) scores less than 60. Feature activity under volatile anesthesia (in comparison to TIVA) was significantly lower for the delta, theta, and alpha frequency bands and for the three features (VC9, ST4, and A0). Further analysis showed that the largest difference between anesthesia types was for feature A0. Conclusions Both EEG frequency bands and novel brain activity features provide evidence that volatile anesthesia further reduces components of brain activity in comparison to TIVA anesthesia. Specifically, A0, which previously showed a correlation with cognitive decline severity and cognitive load, exhibited the most prominent difference between anesthesia types. Together, this study suggests that measuring brain activity during anesthesia using sensitive features can reveal that different anesthesia types may affect brain activity differently, which could affect a patient’s recovery from anesthesia, and consequently reduce post-operative cognitive decline.