1. Patients and groups
This single-center, retrospective study was approved by the Ethics Committee of the General Hospital of Southern Theater command, and written informed consent was obtained from all patients. All methods and procedures were carried out in accordance with the principles contained in the Declaration of Helsinki. 152 patients undergoing radical prostatectomy performed in the Department of Anesthesiology of General Hospital of Central Theater Command from June 2013 to December 2019 were included. Overall cohorts were divided into two groups according to the surgical method they received: 81 cases were included in the group RALRP and 71 cases were included in the group LRP.
The inclusion criteria was that the anesthesia documents were recorded in detail, including airway pressure, PaCO2 before pneumoperitoneum, post-pneumoperitoneum, and after loosening pneumoperitoneum. All surgical procedures were performed by a single surgeon. Patients with heart, lung, liver, kidney, respiratory insufficiencies, disorders of consciousness, preoperative MMSE less than 27 points, or conversion to open surgery during operation were excluded from the data set.
2. Measurements
Demographic variables (age, height, weight, ASA classification, blood pressure, heart rate), the time of preparation for surgery (Tp), time of operation (To), time of anesthesia maintenance (Ta), emergence time (time from cessation of intravenous anesthetic to endotracheal extubation, Te), recovery time (time from endotracheal extubation to discharge from post-anesthesia care unit, Tr), anesthetic dosage (propofol, sufentanil, remifentanil), PaCO2, plasma lactate level, airway pressure at different points (before pneumoperitoneum, post-pneumoperitoneum, after loosening pneumoperitoneum), the incidences of postoperative delirium, utilization of mannitol, IAP, dosage of vasoactive agents (ephedrine, methoxamine and atropine), fluid infusion volume, blood transfusion volume, blood loss, time of postoperative hospitalization(Th) and overall cost were recorded.
3. Methods of anesthesia
In the operating room, all patients were monitored with standard ASA monitors and an upper extremity vein was used for intraoperative infusion. A radial artery cannula was inserted under local anesthesia to monitor blood pressure directly and for arterial blood gas analysis. Nasopharyngeal temperature was monitored by nasal temperature probe. Neuromuscular function was measured using a TOF-Watch acceleromyograph. All patients were induced with etomidate 0.3 mg/kg, sufentanil 0.5 μg/kg and rocuronium 0.9 mg/kg. When TOF ratio was at 0, intubation is performed. After intubation, ventilation was performed to maintain PaCO2 between 35 and 45 mmHg. General anesthesia was maintained with propofol, remifentanil and rocuronium. Vasoactive drugs (ephedrine 5 mg or methoxy 0.5-1 mg) were administered when blood pressure was 20% below patient baseline, and atropine 0.5 mg was administered when heart rate was below 45 beats/min. Esmolol (5mg) was commonly used to treat tachycardia, and nicardipine (0.2-0.5 mg) was used for hypertension. Red blood transfusion was typically initiated with hemoglobin values were lower than 7.0g/dL. 15 minutes before the end of the operation, propofol infusion was stopped and the rate of remifentanil infusion was reduced. When the operation was over, remifentanil infusion was stopped, patients were given dolasetron 12.5mg to prevent vomiting, and 40 mg parecoxib sodium was administered to relieve pain. Extubation occurred when the patient was conscious, spontaneously ventilation recovered, TOF value >90%, SPO2>95%, and with normal vitals. After endotracheal extubation, the patients were continued to be monitored until they were fully conscious, able to cooperative, and vital signs were stable. If postoperative delirium occurred, mannitol was administered to improve cerebral oxygen metabolism, or propofol was given for its sedating effects.
4. Surgical Procedure
After general anesthesia, the patients were kept in the supine. Pneumoperitoneum was induced with CO2 insufflation pressure of 15 mmHg. Following trocar insertion, an IAP of 8 mmHg was set from the previous 15 mmHg, and a remote control was used to place the patients in a ST position. IAP was gradually increased until the surgeon was satisfied with the surgical space. The IAP was recorded throughout the procedure.
5. Statistical analysis
Statistical analysis was performed using SPSS version 25.0. Measurement data are described as mean ± standard deviation. Demographic variables, Tp, To, Ta, Te, Tr, dosage of anesthetic (propofol, sufentanil, remifentanil), IAP, dosage of vasoactive drugs (ephedrine, methoxamine and atropine), infusion volume, blood transfusion volume, blood loss, Th and overall cost were compared using unpaired Student t tests. PaCO2, lactic acid value and airway pressure at different points are repeated measurement data, using repetitive measure analysis of variance. The incidence of postoperative delirium and utilization of mannitol, and ASA scores are count data, using chi-square test. Binary logistic regression analysis was performed with postoperative delirium as the dependent variable, Ta, Te, Tr, PaCO2, and IAP as independent variables, to explore the risk factors for postoperative delirium. A p value < 0.05 was considered statistically significant.