Anesthetic and analgesic techniques
blood loss
BLOOD LOSS
Patient monitoring in the operating room was performed using electrocardiography, pulse oximetry, end-tidal carbon dioxide, invasive arterial pressure, urine output, and the bispectral index (BIS). All patients received general anesthesia induced by intravenous administration of 2 mg/kg of propofol, 0.4 μg/kg of sufentanil, and a single dose of 0.2 mg/kg cisatracurium to facilitate endotracheal intubation. In group C, general anesthesia was maintained by inhalation of 1% sevoflurane and intravenous administration of 2–4 ng/ml (plasma concentration) remifentanil and 1–3 μg/ml (plasma concentration) propofol. In group S, general anesthesia was maintained by the same doses of sevoflurane, remifentanil, and propofol, and an additional target-controlled infusion (CP-600TCI; SLGO, Beijing, China) of 0.2 mg/kg/h S-ketamine (Hengrui Medicine Co., Ltd., Jiangsu, China). The oxygen inhalation flow rate was 50% during anesthesia, and the ventilator was adjusted to maintain the end-tidal carbon dioxide at 35 to 45 mmHg. Sevoflurane and propofol concentrations were adjusted to maintain an adequate depth of anesthesia according to theBIS (spectral entropy value of 40 to 60). Remifentanil concentrations were adjusted by hemodynamic changes. Intravenous sufentanil (10 μg) and ketorolac tromethamine (15 mg) were administered 30 min before the end of the surgery. Tropisetron (5 mg) was administered 15 min before the end of the surgery.S-ketamine was discontinued 30 min before the end of the surgery. Following surgery, patients were connected to PCIA pump containing 120 ml of 2 μg/kg of sufentanil, 90 mg ketorolac tromethamine, and 20 mg tropisetron in 0.9% sodium chloride solution in group C. An additional 50 mg S-ketamine was added in group S. The PCIA pump was programmed to deliver a loading dose of 2 ml, a 1 ml/h basal infusion, a 2 ml bolus dose with a lockout interval of 10 min, and a maximum dose of 13 ml/h. At the end of the operation, the patient was transferred to the post-anesthesia care unit and then transferred to the ward after extubation. The dose of S-ketamine infusion during surgery, total intraoperative infusion, red blood cell transfusion requirement, blood loss, total urine output, and general anesthesia time were recorded.