Effect of Sevoflurane and Remimazolam on Arterial Oxygenation During One-lung Ventilation

One lung ventilation (OLV) is a mechanical ventilation method used during thoracic surgery to collapse the non-ventilated lung and secure the surgical field. During one lung ventilation, the pulmonary artery of the collapsed lung undergoes vasoconstriction in response to hypoxia, which increases the blood flow of the normally ventilated lung as a compensatory physiological response. This is known as hypoxic pulmonary vasoconstriction (HPV). Therefore, by using HPV, arterial blood oxygenation can be maintained and pulmonary shunting can be reduced, preventing hypoxemia during one lung ventilation. The two most commonly used anesthetics in thoracic surgery are sevoflurane, an inhaled anesthetic, and propofol, an intravenous anesthetic. Previous studies have shown that there were no significant differences between two anesthetics on arterial oxygenation during one lung ventilation because sevoflurane administered in clinical concentrations of 1 minimum alveolar concentration (MAC) resulted in similar changes in shunt fraction as did propofol. However, the effect of remimazolam on arterial blood oxygenation and intrapulmonary shunt during one lung ventilation has not been revealed. Therefore, this study is designed to compare the effect of remimazolam and sevoflurane anesthesia on arterial oxygenation during one lung ventilation in patients undergoing video-assisted thoracoscopic surgery.