Changes in SpO2 during total intravenous anesthesia combined with propofol and SpO2 during one-lung anesthesia ventilation

We retrospectively examined SpO2 during one-lung anesthesia (OLA). One hundred and fifty patients of ASA 1 or 2 for thoracoscopic surgery were anesthetized with propofol and fentanyl (n = 93) or pentazocine (n = 57) and mechanically ventilated with FIO2 = 0.6 in the lateral decubitus position. Twelve patients (8%) developed SpO2 < or = 95% in the first 20 minutes of OLA. It has been reported that hypoxemia during OLA occurs in 13-40% of patients under inhalation anesthesia with FIO2 = 1.0. Our results show the total intravenous anesthesia using propofol is useful to maintain SpO2 during OLA. SpO2 during OLA tended to fall in the patients for right side operation, with lower SpO2 during two-lung ventilation and higher body mass index (BMI). However BMI has never been reported as a predictor of hypoxemia during OLA. A gravity-dependent mechanism is considered to be more responsible for the dependent regional volume reduction during OLA in patients in the lateral decubitus position.