ORI MONITORING IN LOW AND NORMAL FLOW ANESTHESIA APPLICATIONS

Overview

Oxygen administration is essential in the perioperative period to prevent hypoxia; however, excessive oxygen may cause hyperoxia and related complications. While pulse oximetry is effective in detecting hypoxemia, it is insufficient for identifying hyperoxia when SpO₂ exceeds 97%, often necessitating invasive arterial blood gas analysis. The Oxygen Reserve Index (ORI) is a noninvasive, real-time monitoring parameter reflecting moderate hyperoxic ranges (PaO₂ 100-200 mmHg) and provides early warning of oxygenation changes before SpO₂ alterations occur. Combined use of ORI and pulse oximetry may enable optimal oxygen titration and prevention of both hypoxemia and hyperoxemia. Laparoscopic nephrectomy is widely performed due to its clinical advantages. In our practice, low and normal fresh gas flow anesthesia are commonly used. Low-flow anesthesia offers benefits such as preservation of heat and humidity, reduced cost, and improved airway physiology. This study aims to determine optimal oxygenation levels during laparoscopic nephrectomy under low and normal fresh gas flow conditions using ORI monitoring.

Oxygen is routinely administered to patients in the perioperative setting to prevent the harmful effects of hypoxia. However, high oxygen concentrations may lead to hyperoxia, which can result in significant complications. Therefore, early detection of both hypoxemia and hyperoxemia during the perioperative period is crucial. Pulse oximetry is highly effective in detecting hypoxemia; however, it is insufficient for evaluating oxygenation when SpO₂ exceeds 97%, limiting its usefulness in identifying hyperoxia. In such cases, arterial blood gas analysis, an invasive method, is typically required. The Oxygen Reserve Index (ORI) is a noninvasive, real-time, and continuous monitoring parameter used to assess oxygenation status. ORI values range from 0 to 1 and reflect arterial partial oxygen pressure levels between approximately 100 and 200 mmHg. Importantly, ORI provides an early warning of deteriorating oxygenation before any detectable changes occur in SpO₂. The combined use of ORI and pulse oximetry may facilitate more precise titration of inspired oxygen concentration and help prevent both hypoxemia and hyperoxemia. Laparoscopic surgery offers several advantages, including reduced blood loss, improved wound healing, decreased postoperative pain, and shorter hospital stays. Accordingly, laparoscopic techniques are frequently employed for nephrectomy procedures in our clinic. Depending on clinician preference, low, normal, and high fresh gas flow rates are commonly and safely used in our practice. Low-flow anesthesia provides benefits such as preservation of heat and humidity within the respiratory system, reduced costs, and decreased environmental pollution. Additionally, improved preservation of mucociliary clearance contributes to better maintenance of airway physiology. In high-risk and major surgeries such as laparoscopic nephrectomy, ORI monitoring is routinely utilized in our clinic to minimize the risks of hypoxemia and hyperoxemia. In this study, we aim to determine optimal oxygenation levels during laparoscopic nephrectomy procedures performed under low and normal fresh gas flow conditions.