Oxygen Reserve Index Monitorization in Minimally Invasive Surgery for Thoracic deformity

A total of 128 patients under 18 years age undergoing elective minimal invasive repair of pectus excavatum (MIRPE) surgery will be recruited. The patients will be randomized into two groups by sealed envelope method. In the control group (Group C) patients will be followed up with continuous SpO2 measurement as standard. In the study group (Group O) continuous oxygen reserve index (ORI) monitoring together with perfusion index (PI) measurements in addition to SpO2 will be applied. ORI values will be monitored by Root® with Radical-7® (Masimo Corp., Irvine, CA, USA) device. Standard intravenous general anesthesia induction (propofol 2-3 mg/kg, remifentanil 0.5-1 µg/kg and rocuronium bromide 0.6 mg/kg) and desflurane-remifentanil based maintenance (desflurane 6% in oxygen-air mixture and remifentanil infusion at a rate of 0.1-0.25 µg/kg/min) will be used. The patients’ demographic variables; comorbidities; operation and anesthesia durations; amount of intravenous fluid administered intraoperatively; pre-induction, pre-first and -second pneumothorax, and postoperative ORI values, mean arterial pressure, temperature, PI, end-tidal carbon dioxide levels will be recorded; as well as postoperative complications, and lengths of hospital stays. After induction, FiO2 will be adjusted to 40% and titrated between 60-100% with the onset of pneumothorax according to the decrease in ORI in Group O and SpO2 in Group C. A decrease of 0.05 from the highest ORI value will be accepted as the beginning of the ORI decrease, and a 1% decrease from the SpO2 value will be accepted as the beginning of the SpO2 decrease, and application times of FiO2 <60% will be recorded. FiO2 will be titrated by increasing or decreasing by 20% and the duration of FiO2 values equal to or <60% and FiO2 >60% will be recorded until the end of the operation.