During laparoscopic procedures, certain physiological changes occur due to the creation of pneumoperitoneum. One such change is the reduction in portal venous blood flow, which can lead to decreased liver perfusion and acute liver cell injury. Additionally, due to an increased alveolar-arterial oxygen pressure gradient, postoperative atelectasis may occur, leading to hypoxia.

In other words, the increased intra-abdominal pressure during laparoscopic surgery-along with the effects of patient positioning and mechanical ventilation used during anesthesia-can worsen low blood oxygen levels, especially in patients with already reduced lung compliance and higher metabolic demands. This makes close monitoring of oxygenation crucial.

The Oxygen Reserve Index (ORI) is a relatively new tool that can help monitor both high oxygen levels (hyperoxemia) and drops in oxygen (desaturation) before they become clinically apparent. Studies have shown that ORI values range from 0 to 1, with an ORI of 0 typically corresponding to a PaO₂ level between 80-125 mmHg. A downward trend in ORI can act as an early warning sign of hypoxemia, giving clinicians a chance to act before it's too late.

Many studies have highlighted the potential harms of using high oxygen concentrations during surgery. For example, while most hospitals still give patients 100% oxygen before anesthesia (a process called preoxygenation), recent evidence suggests this might increase the risk of atelectasis. Therefore, using 80% or less oxygen is now being recommended in many settings. High oxygen levels have also been linked to increased oxidative stress in the body.

In this study, we aim to investigate whether monitoring ORI during extubation can help us detect and prevent both hyperoxemia and hypoxemia-situations that standard pulse oximetry often misses. We plan to compare two groups of patients: one receiving conventional 100% oxygen during extubation, and another receiving 80% oxygen. By monitoring ORI values in both groups, we hope to better understand how different oxygen levels affect patient safety and outcomes.

Inclusion Criteria:

• Age: 18-75
• ASA: I-II
• Scheduled for elective laparoscopic surgery
• BMI <35

Exclusion Criteria:

• Patients undergoing emergency surgery due to trauma
• Patients with ASA physical status classification III or IV
• Patients requiring intensive care unit admission
• Patients with active, clinically symptomatic anemia
• Patients with heart failure
• Patients with known allergy to the sensor material to be used
• Patients with difficult mask ventilation or difficult intubation
• Patients with a platelet count below 30,000/mm³
• Patients with a history of gastrointestinal bleeding within the past 6 months
• Patients with a history of bleeding diathesis or increased risk of intracerebral hemorrhage
• Patients with oliguria and/or those who required dialysis or underwent dialysis within one month prior to surgery
• Patients with a known hypersensitivity reaction to any anesthetic or analgesic drug used in the study
• Patients who do not wish to participate in the study

Sixty volunteer patients, aged between 18 and 75, with a Body Mass Index (BMI) below 35 and ASA class I and II, who are scheduled to undergo laparoscopic hysterectomy, will be included.