Anesthetic procedures
The anesthetic protocol was carefully standardized in all patients. Patients were not administered premedication or an intravenous line before entering the operation room. After the patients had entered the operating room, a peripheral intravenous line was established by the nurse. Then, radial arterial puncture and double-lumen right internal jugular catheterization were performed by the attending anesthetist under local anesthesia. Patients were then administered sufentanil (0.8 µg/kg), etomidate (0.3 mg/kg), and cis-atracurium (0.3 mg/kg) for induction of general anesthesia. General anesthesia was maintained with propofol, remifentanil, and cis-atracurium, as well as inhalational sevoflurane (0.5–1%). During anesthetic induction, the inhalational oxygen concentration was 100%, and a 50% oxygen-to-air mixture was used to maintain anesthesia. During surgery, the bispectral index score(BIS) of anesthetic depth was maintained between 40 and 60. Standard intraoperative monitoring included electrocardiography, pulse oximetry (SpO