Effect of ORI-guided Oxygen Titration on Oxidative Stress in Rhinoplasty Surgery

The Effect of Oxygen Reserve Index Guided Oxygen Titration on Oxidative Stress in Rhinoplasty Surgery: A Randomized Controlled Trial

The aim of this study is to evaluate whether the use of Oxygen Reserve Index (ORİ) can prevent hyperoxia in patients undergoing rhinoplasty surgery and whether it can reduce oxidative stress caused by hyperoxia.

ORI is a continuous, non-invasive parameter provided by new-generation pulse oximeters utilizing multi-wavelength pulse oximetry technology. ORI serves as an important monitoring tool for detecting both hyperoxemia and desaturation in patients with decreased PaO₂ levels. Studies have demonstrated that ORI provides values within a range of 0 to 1, and an ORI value of 0 corresponds to a PaO₂ level between 80 and 125 mmHg.

Oxygen is commonly used in clinical practice to prevent or treat hypoxia; however, excessive use may lead to oxidative stress. Oxidative stress is defined as a disruption of the oxidative balance resulting from an increased generation of reactive oxygen species (ROS) during cellular metabolism and an insufficient level of antioxidants to detoxify them. ROS are formed by the reaction of molecular oxygen with H₂O, the most stable form of oxygen. In this reaction, the stepwise addition of electrons to molecular oxygen (O₂) leads to the formation of superoxide anion (O₂ˉ), hydrogen peroxide (H₂O₂), and hydroxyl radical (-OH). Among these, the hydroxyl radical is the most reactive form of oxygen radicals.

Although ROS are essential for normal cellular functions such as intracellular signaling and defense against external threats, their excessive production can lead to molecular and cellular dysfunction. Excessive ROS attack nucleotide bases in nucleic acids, amino acid side chains in proteins, and double bonds in unsaturated fatty acids, resulting in oxidative stress that damages DNA, RNA, proteins, and lipids, leading to structural and metabolic changes in cells.

The primary aim of the investigators in this study is to determine whether ORI-guided oxygen titration during rhinoplasty surgery can help prevent hyperoxia and reduce oxidative stress compared with conventional oxygen therapy. To evaluate oxidative stress, thiol-disulfide balance and ischemia-modified albumin (IMA) levels will be assessed in the participants.

Inclusion Criteria:

• classified as ASA physical status I or II

Exclusion Criteria:

• under 18 years of age
• ASA classification greater than II
• Mallampati score of 3 or 4
• findings suggestive of difficult intubation during physical examination
• any pathological findings on chest X-ray evaluation (e.g., pleural effusion, nodular density increase, emphysema, atelectasis, calcification, mediastinal widening, or infiltration)
• a history of circulatory disorders
• hematocrit or hemoglobin values outside the normal range (Hemoglobin: 12-16 g/dL for males, 11-14 g/dL for females; Hematocrit: 36-48% for males, 33-42% for females)
• a known hypersensitivity to any anesthetic agent to be used in the study.