This single-center randomized interventional study evaluated the biological effects of two perioperative oxygen strategies in adults undergoing elective laparoscopic lower abdominal surgery under standardized general anesthesia. Participants were assigned to receive either normoxia (FiO2 0.35) or hyperoxia (FiO2 0.80) after intubation and throughout the intraoperative period. The study assessed perioperative changes in circulating biomarkers related to pulmonary epithelial stress, endothelial glycocalyx injury, oxidative stress, and inflammation, together with blood gas and hemodynamic parameters. The study was completed before registration and is being registered retrospectively.