2.1 General information
This study was approved by the Ethics Committee of the First People's Hospital of Taicang and the informed consent forms were signed for all enrolled patients. All methods were carried out in accordance with relevant guidelines and regulations or Declaration of Helsinki. A total of 60 patients who underwent elective gastrointestinal tumor surgery in our hospital from January 2019 to December 2021 were included in the study. Inclusion criteria: Patients of any gender, 65–80 years old, ASA grades II-III, and retrograde elective gastrointestinal surgery. Exclusion criteria: operation duration < 2 hours; History of chemotherapy or radiotherapy before surgery; another previous history of abdominal surgery; Long-term history of opioid or neuropsychiatric drug use; Combined history of neurological diseases such as Alzheimer's disease and Parkinson's disease or cognitive dysfunction; Postoperative transfer to ICU or secondary surgery; Hearing or language expression disorders; Patients with coagulation disorders; The puncture point has skin infection; Allergic to any drug used in this study; The patient refused to continue participating in the study.
2.2 grouping and processing
In this study, the enrolled patients were randomly divided into two groups according to the random number table: the control group (Group C, 30 cases) and the paravertebral nerve block group (PVB group, 30 cases). The anesthesiologists who performed anesthesia management and the researchers who followed up after the operation were blinded. Anesthesia management and nerve block procedures in this study were performed by experienced anesthesiologists.
All patients included in the study did not receive preoperative medication, and monitoring was established after the patient entered the room: percutaneous oxygen saturation (SpO2), non-invasive blood pressure monitoring, electrocardiogram, and Bispectral Index(BIS). After the peripheral venous access was opened, lidocaine local anesthesia was applied for radial artery puncture catheterization and invasive arterial blood pressure was monitored. After intravenous injection of 1mg midazolam and 5 µg sufentanil citrate in the PVB group, the patient was asked to lie on his/her side. After routine disinfection and drape laying, he/she was scanned and positioned along the spine by Sonite ultrasound apparatus so that the direction of the convex array probe was parallel to the ribs and positioned to the T8 vertebral body. The thoracic para-space was identified in the ultrasound image, and the needle was inserted in the plane. After the puncture needle broke through the costal transverse process ligament and drew back the airless, blood, and cerebrospinal fluid, 20ml of 0.375% ropivacaine was injected, and the sliding pleural downforce was visible. Complete the other side of the T8 paravertebral block in the same way. The rats were observed for 20 min after the block and the block plane was tested by acupuncture. If there was no obvious block plane, the block was considered a failure. Group C has no special treatment.
2.3 Anesthesia methods and postoperative analgesia
All patients were under intravenous anesthesia during the operation. midazolam 0.04 mg/kg, etomidate 0.3 mg/kg, sufentanil citrate 0.5 µg/kg and atracurium cis-benzenesulfonate 0.2 mg/kg were used for anesthesia induction. After induction, intubation was performed orally under the guidance of a visual laryngoscope and connected to the anesthesia machine for mechanical ventilation. The catheter was fixed. The lower part of the head was taken, deep venipuncture was performed through the right internal jugular vein of the patient, and catheterization was performed. During the operation, the pulmonary protective ventilation strategy was adopted: tidal volume of 6–8 mL/kg, the inhaled oxygen concentration of FIO2 50–80%, PEEP 4–8 mmH20, and suction to shout ratio of 1: 2. The respiratory frequency was adjusted to 12–15 times/min to maintain the end-tidal carbon dioxide (PetCO2) 35 ~ 40 mmHg during the operation. The anesthetics were maintained by continuous intravenous infusion of propofol 0.08–10 ~ 15 µg kg − 1 min − 1, atracurium besylate 0.05–0.1 mg kg − 1 h − 1, and remifentanil 0.15–0.3 µ g kg − 1 min − 1, with intermittent addition of sufentanil citrate 10–15 µ g. During the operation, medication dosage was adjusted according to the monitored values of patients' BIS values to maintain the fluctuation of BIS values within the range of 40–60. The intraoperative blood pressure management goal of the patient was to give appropriate fluid replacement and vasoactive drugs such as phenylephrine and ephedrine within the range of 20% above and below the preoperative basic blood pressure to achieve the target value.
Atracurium besylate was stopped 20min before the end of the operation. Propofol was stopped when the surgeon sewed the skin. Remifentanil and Tenet 40mg were added after the operation. The patient was transferred to PACU with a catheter. Patient-controlled intravenous analgesia (PCIA) pump was used in all postoperative analgesia programs, and the prescription was as follows: 100 µ g of sufentanil citrate + 10 mg of tropisetron hydrochloride; normal saline was added for dilution to 100 ml; no background dose was given; bolus dose was 2 ml, and the locking time was 15 min. Antagonists were not used in all patients during the awakening period after the operation until the patients were fully awake and able to respond to calls, the throat reflex, swallowing reflex and cough reflex had fully recovered, and the tidal volume and minute ventilation volume had returned to normal. All patients were observed in the PACU for 1h after extubation, and no special cases could be transferred to the ward.
2.4 Observation indicators
The patients in the two groups received a mini-mental state examination (MMSE) one day before surgery (T0), one day after surgery (T1), and three days after surgery (T2), which included five aspects: memory, computational power, memory, language power, and directional power. The total score was 30 points. The higher the score was, the stronger the cognitive function would be . The peripheral venous blood was collected from the patients at time points T0, T1, and T2, and the enzyme-linked immunosorbent assay (ELISA) was used to determine NSE and detect the concentration of neuron-specific enolase, NSE). Record the operation and anesthesia-related information: operation duration, anesthesia duration, extubation duration, type and the total amount of infusion liquid during the operation, intraoperative bleeding and urine volume, and the total dosage of propofol and opioids during the operation.
2.5 Statistical methods
All data were statistically analyzed by SPSS 15.0. Measurement data of normal distribution were expressed as mean standard deviation, t-test was used for inter-group comparison, and one-way analysis of variance was used for comparison within the group at different time points. Enumeration data were expressed as a rate (%) and inter-group comparisons were performed by Chi-square test or Fisher's exact probability method. P < 0.05 indicated that the difference was statistically significant.