Discussion
neurological and gastrointestinal complications
POSTOPERATIVE COMPLICATIONS
In the randomized controlled trial, the impact of the raw EEG guidance of anesthesia on postoperative complications after surgery in older adults (≥ 60) undergoing major abdominal surgery was assessed. There was no statistically significant difference between the two groups in terms of postoperative respiratory, cardiovascular, neurological and gastrointestinal complications and all-cause mortality at 30 days postoperatively. There was no statistically significant difference in the number of intraoperative BS between the two groups, but rEEG-guided anesthesia management significantly reduced the time patients spent in BS. In post hoc exploratory analyses, low frontal alpha power was found to be independently linked to POD, and that rEEG-guided anesthesia allowed individual regulation of depth of anesthesia to avoid over-anesthesia in patients with a fragile brain, while ensuring the depth of anesthesia required in older patients with a healthy brain.As the brain is the target organ for general anesthesia, with the continuous research and development of EEG monitoring, some experts advocate the incorporation of EEG-based monitoring into routine anesthetic management. EEG monitoring can avoid too light anesthesia and prevent the occurrence of intraoperative awareness, while EEG monitoring can avoid too deep anesthesia, which usually leads to prolonged recovery time as well as impaired quality of recovery for patients [Gamma-aminobutyric acidergic (GABAergic) anesthetics, i.e., sevoflurane, and propofol, generate stereotyped slow (0.1–1 Hz) activity and frontal alpha (8–12 Hz) oscillations of EEG in the process of unconsciousness, both of which are quantified by using a power spectral analysis. A correlation between frontal alpha band activity and preoperative cognitive function has been found which was not present in other EEG bands. Also, EEG alpha band activity strength is linked to age [This study has several limitations. Firstly, the same anesthesiologist may manage patients in either the rEEG-guided group or the routine care group. Although the anesthesiologists managing the routine care group were masked to the EEG, their previous experience of offering rEEG-guided anesthesia care could have not only enabled them to know more about the anesthesia propofol maintenance but also potentially affected the dosage level. As a result, this research is likely to under-evaluate the actual difference between rEEG-guided and routine care. Secondly, in this research, the explored EEG data comes from the frontal 4-channel pathway, and therefore the analysis only focuses on frontal alpha oscillations in the EEG during unconsciousness, which cannot evaluate other cortical EEG activity. Therefore, high-density EEG research is needed to improve the reliability and utility in the recognition of vulnerable brains and measuring anesthetic depth. Thirdly, a significant correlation was found between the frontal alpha power and POD probability. Taking into account that frontal alpha power is seen as an underlying brain frailty trait, the intervention effect size may be larger when including more cognitively impaired patients, and therefore further validation within bigger research is needed.