Chronic SSRI/SNRI Use and Intraoperative Propofol Requirements

The goal of this observational study is to learn whether long-term use of selective serotonin reuptake inhibitor (SSRI) or serotonin-norepinephrine reuptake inhibitor (SNRI) antidepressants is related to the amount of propofol needed during planned spine surgery. Propofol is a medicine given through a vein to produce and maintain anesthesia. The main questions this study aims to answer are: * Do patients who regularly take an SSRI or SNRI need a different total amount of propofol during surgery than patients who do not take these medicines? * Are there differences in propofol and remifentanil use, depth of anesthesia, vital signs, or recovery time between the study groups? The study will include 216 adults undergoing planned spine surgery. Researchers will compare 108 participants who regularly take an SSRI or SNRI with 108 participants who do not take these medicines. All participants will receive routine anesthesia care. The study will not start, stop, or change any antidepressant treatment, and participants will not be randomly assigned to a group. Researchers will record the amount of propofol and remifentanil used during surgery, blood pressure, heart rate, oxygen level, depth of anesthesia, and recovery time.