Anesthesia Brain Monitor

This study will try to elucidate the neural responses of neonatal patients to surgery-level propofol infusions during induction and maintenance of anesthesia. The main objective is to elucidate the EEG patterns of neural activity that can reliably reflect the level of hypnotic depth in full term neonates undergoing propofol anesthesia based on the classification of EEG into states and the characterization of discrete neonatal EEG events.

The goal of this observational study is to determine whether macrophage/monocyte mediated inflammatory signaling contributes to reduced anesthetic requirements in older adults undergoing major abdominal surgery. The main questions it aims to answer are: * Is there a difference in anesthetic dosing requirements (minimum effective dose) between young and older patients undergoing major abdominal surgery? * How do electroencephalographic (EEG) signatures under anesthesia correlate with age and systemic inflammatory markers? * Is there an association between age, levels of circulating inflammatory cytokines, and monocyte/macrophage phenotypes with anesthetic requirements? If there is a comparison group: Researchers will compare older adult patients undergoing major abdominal surgery to younger adult patients undergoing major abdominal surgery to see if macrophage/monocyte-mediated inflammatory signaling influences anesthetic sensitivity and the risk of postoperative neurocognitive complications in the older population. Participants will: * Receive general anesthesia for major abdominal surgery, with continuous recording of anesthetic dose requirements. * Undergo electroencephalographic (EEG) monitoring during the anesthetic period. * Provide blood samples for the measurement of circulating inflammatory cytokines and the assessment of monocyte phenotypes. * Provide peritoneal tissue samples (collected during surgery) to evaluate tissue macrophage populations. * Provide cerebrospinal fluid (CSF) samples to assess biomarkers of blood-brain barrier permeability.