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.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
PREVENTION
Masking
QUADRUPLE
Enrollment
60
In Group R, FiO₂ was titrated between 30% and 50% under the guidance of ORI and SpO₂ values. Accordingly, if SpO₂ was ≥ 98%, FiO₂ was reduced in 5% increments to a minimum of 30%, aiming to achieve an ORI value of 0 or as close to 0 as possible.
In Group C, FiO₂ was maintained at 50% throughout the surgery, provided that SpO₂ remained ≥ 98%.
Kartal Dr. Lütfi Kırdar City Hospital
Istanbul, kartal, Turkey (Türkiye)
Change in thiol-disulfide balance.
Plasma native thiol, total thiol, and disulfide levels will be measured. The disulfide-to-thiol ratio will be used as a marker of oxidative stress. Unit of Measure: µmol/L
Time frame: preoperative to end of surgery (before awakening)
Change in ischemia-modified albumin (IMA) levels.
Serum IMA levels will be measured as an indicator of oxidative stress. IMA reflects modification of the N-terminal region of albumin by reactive oxygen species (ROS). Unit of Measure: Absorbance Units (ABS units)
Time frame: preoperative-end of surgery (before awakening)
PaO₂ levels.
To compare intraoperative PaO₂ changes between ORI and Control groups. Arterial blood gas samples were obtained from all patients after intubation, at the 2nd hour of surgery, and at the end of the procedure before awakening.
Time frame: From baseline (after intubation) to end of surgery (before awakening)
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