Our research was approved by the Ethics Committee of Third Xiangya Hospital, Central South University (No:2019-S473). We reviewed the medical records of patients undertaking colorectal surgery at the third Xiangya hospital of Central South University from January, 2015 to January 2019. Eligibility criteria included patients who were over 18 years old, American Society of Anesthesiologists (ASA) status Ⅰ-III, receiving selective colorectal surgery under general anesthesia and PCIA for postsurgical analgesia. Exclusion criteria were patients unable to communicate, wound infection after surgery, receiving a second operation.
On entering the surgery room, patients’ vital signs were monitored by electrocardiogram, invasive arterial blood pressure, pulse oximetry and bispectral index. General anesthesia was induced with fentanyl (4-6 μg/kg) or sufentanil (0.4-0.6 μg/kg), propofol (1.5-2 mg/kg), midazolam (2-3 mg), rocuronium (1 mg/kg) or cisatracurium besylate (0.15-0.2 mg/kg). Anesthesia was maintained both with intravenous infusion propofol 4 to 7 mg/kg/h, remifentanil 6 to 10 μg/kg/h, and inhalation of 1% to 2% sevoflurane. Fentanyl or sufentanil was used when signs of inadequate analgesia were evident intraoperatively such as increased heart rate or blood pressure. 0.05mg/kg of cisatracurium was administered at 30-40 minutes intervals. All patients received 0.25 mg palonosetron hydrochloride intravenously before suture.
For those patients who received TAP block, bilateral TAP block was performed by ultrasound (SonoSite EdgeⅡ, American) before anesthesia induction. 40ml of 0.5% ropivacaine (AstraZneca AB, Sweden, 20 ml each side) was injected into the transversus abdominis plane under real-time ultrasound guidance.
Postoperatively, electronic analgesic pump with wireless analgesic system was used for 48 hours of PCIA (Renxian Medtech, Jiangsu). The PCIA pump was filled with sufentanil 150 μg, azasetron 10 mg, diluted to 150 ml with 0.9% normal saline. It was programmed to give 1.5-2 ml/h background infusion with a 1.5-2 μg bolus of sufentanil solution, with a 5min lockout time. Patients were routinely informed that they could control the pain by pressing a self-controlled button to only slight pain. Pain was assessed twice a day at rest and during movement with an 11-point Numeric Rating Scale (NRS) (0 = no pain; 10 = pain ‘as bad as you can imagine’) by the same nurse of acute pain service group within 48h after operation.
After discharged from hospital, postoperative follow-up team contacted patients via telephone at three months and six months after operation to complete pain evaluation (NRS score and painful place).
The data extraction
Patients' data including patients’ ASA status, sex, age at the time of operation, body mass index was extracted from medical records. Patients' information about surgical and anesthetic management such as anesthesia duration, surgery duration, perioperative opioid dose and pain scores was extracted from Anesthesia records. All patients were allocated to two groups: group TP were those patients who received TAP block and PCIA; and group P were those patients who only received PCIA.
In order to facilitate comparison, fentanyl 0.1mg was equivalent to sufentanil 0.01mg. Considering that remifentanil is an ultra-short-acting opioid, we analyzed it separately. Opioid usage was analyzed with the unpaired t-test between two groups. Two-way repeated measures anova was used for NRS scores of 24 hours, 48 hours, 3 months and 6 months after surgery. The chi-square test was used for comparisons of categorical data. Quantitative data were expressed as mean±SD and categorical variables as percentages. Data were analyzed with the SPSS software version 22.0 (SPSS Inc., Chicago, IL). Significance was determined at P＜0.05.
Patient and public involvement
Patients and the public were not involved in planning, design, or interpretation of the study. The study involved examination of existing claims data and no participants were recruited for this analysis. This research was done without patient involvement. Patients were not invited to comment on the study design and were not consulted to develop patient relevant outcomes or interpret the results. Patients were not invited to contribute to the writing or editing of this document for readability or accuracy.