Patient enrollment
Sixty participants in our hospital were contraindicated for spinal anesthesia and required general anesthesia for a cesarean section from March 1, 2022, to April 10, 2022, and were selected. The participants were randomly divided into two groups according to a 1:1 ratio through the central randomization network system: the ESPB combined with the general anesthesia group (Group E) and the general anesthesia group (Group G) (Fig. 1). This study was approved by the Ethics Committee of Women and Children's Hospital of Chongqing Medical University and registered at www.clinicaltrials.gov under the number ChiCTR2200056337(04–02-2022), following the tenets of the Declaration of Helsinki. Written informed consent was obtained from all the participants.
The inclusion criteria were as follows: (1) singleton pregnancy for elective cesarean section; (2) spinal anesthesia prohibited (due to reasons such as spinal deformity, spinal trauma, and coagulation dysfunction); (3) American Society of Anesthesiologists grade II; and (4) normal cognitive function.
The exclusion criteria were as follows: (1) allergy to local anesthetics; (2) body mass index (BMI) > 35 kg/m2; and (3) severe heart disease, hypertension, diabetes, etc.
Patient Management
General anesthesia in both groups was performed by total intravenous anesthesia, and anesthesia induction was performed with 4–6 μg/ml propofol and 4–6 ng/ml remifentanil TCI target-controlled infusion, 0.6 mg/kg rocuronium before endotracheal intubation. Anesthesia was maintained with 2.5–4 µg/ml propofol and 4–6 ng/ml remifentanil TCI target-controlled infusion. The utility of BIS for sedation management during monitored anesthesia care was maintained within the range of 40–60. After the fetus was delivered, sufentanil 0.2 μg/kg was injected intravenously, and rocuronium was administered during the operation as needed. All patients were transferred to the post-anesthesia care unit after surgery. The patient-controlled intravenous analgesia (PCIA) formula comprised fentanyl 0.2 mg + tramadol 80 mg + dexamethasone 10 mg to 100 mL 0.9% normal saline, with a 2 mL/h background infusion and a 2 mL bolus dose, with a lock time of 15 min.
Group E: Thirty minutes before induction of general anesthesia, bilateral ESPB was performed under ultrasound guidance by the same anesthesiologist in the preparation room for anesthesia. The patients were instructed to remain in the lateral decubitus position. The ultrasound probe was placed on the spinous process of the 9th thoracic vertebra along the short axis. Subsequently, the probe was slid slightly in the lateral direction until the transverse processed image was visible. With subcutaneous infiltration of 3 mL of 2% lidocaine, a 22G blunt needle (Spinocan, B. Braun Melsungen AG, Germany) was introduced from the outside toward the transverse process (T9) using the in-plane method until the needle tip crossed all the muscles. Subsequently, 20 ml of 0.25% ropivacaine was injected between the transverse process and the deep surface of the erector spinae on each side.
Group G: with no ESPB.
Pain measurements and outcomes
Heart rate (HR) and mean arterial pressure (MAP) were recorded 10 min before the start of anesthesia (T0), at the induction of anesthesia (T1), at skin incision (T2), at fetal delivery (T3), and at the end of the operation (T4). The intraoperative propofol and remifentanil dosages, fetal delivery time, and emergence time were recorded. The VAS and BCS comfort scores of patients were measured at 2 h, 6 h, 12 h, and 24 h after the operation. The VAS score is ranked on a point system from 0–10; 0 points: no pain; less than 3 points: mild pain, which the patient can tolerate; 4–6 points: pain that affects sleep but can be tolerated; 7–10 points: the patient has increasingly severe pain that is unbearable. The BCS comfort score was ranked as follows: 0, persistent pain; 1, no pain at rest; severe pain when breathing or coughing; 2, no pain at rest; mild pain during breathing or coughing; 3, no pain during deep breathing; 4, no pain during deep breathing and coughing; record the number of PCA boluses within 24 h after surgery; and record the incidence of nausea and vomiting within 24 h after the operation. All data were obtained by the same anesthesiologist, who was blinded to the group assignment and was not involved in implementing the nerve block.
Statistical analysis
The sample size estimation was based on the number of PCA boluses within 24 h of the pilot study by our team. To detect a 20% change in PCA boluses with an error of 0.05 and a power of 80%, the minimum sample size was found to be 23 patients per group. Thirty patients were enrolled in each group to account for dropouts.
SPSS 20.0 statistical software was used for data analysis, normally distributed measurement data were expressed as mean ± standard deviation (intraoperative propofol and remifentanil dosages, fetal delivery time, and emergence time) or as number (%) (incidence of nausea and vomiting), paired t-test was used for intra-group comparison, group t-test was used for inter-group comparison. A two-way repeated- measures analysis of variance with the Bonferroni post hoc -test was used to compare the VAS, hemodynamic variables, and BCS within and between the two groups. Statistical significance was defined as P < 0.05.
