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.

Inclusion criteria

• Patients undergoing video-assisted thoracoscopic surgery
• 19 years of age or older, less than 80 years old
• The American Society of Anesthesiologists (ASA) classification I-Ⅲ physical status

Exclusion criteria

• Patients with known allergy to benzodiazepine, propofol
• Patients with galactose intolerance, Lapp lactase deficiency, glucose-galactose malabsorption
• Patients with hypersensitivity to Dextran40
• Patients with end stage renal disease requiring hemodialysis
• Patients with history of acute angle glaucoma
• Emergency operation
• Patients with unstable hemodynamics requiring inotropics
• Patients with preoperative oxygen supplement
• Preoperative forced expiratory volume (FEV1) less than 40% of predicted
• Preoperative ejection fraction less than 50%