Patients and study design
128 patients undergoing elective SILC were enrolled in this study from February 2019 to April 2019 at Affiliated Hospital of Nantong University. Inclusion criteria: between 18 and 59 years of age, men and women are not limited, American Society of Anesthesiology (ASA) score is ⅠorⅡ, Body Mass Index(BMI) is 18-30 kg/㎡, Patients with preexisting neuropathy, coagulopathy, local skin infection, hepatic, renal or cardiorespiratory failure, local anesthetic allergy, pregnancy, complications of gallstone with gallbladder perforation, diffuse peritonitis and acute pyogenic cholangitis were excluded.
The study was registered prospectively with the Chinese Clinical Trial Registry(reg no.ChiCTR1900020738)(reg no.ChiCTR1900020738), obtained ethics committee of Affiliated Hospital of Nantong University approval (approved number: 2018-K067), and written informed consent.
Randomization and blinding
All 116 patients, 64 males, 52 females, scheduled for elective single-incision laparoscopic cholecystectomy, were randomly divided into four groups by using a computer-generated random sequence concealed in consecutively numbered opaque sealed envelopes, which were opened on the morning of surgery. The anesthesiologist performed anesthesia and nerve block and postoperative assessors were blinded to grouping.
Anesthesia
116 patients were induced with intravenous midazolam 0.1mg/kg, propofol 2mg/kg, sufentanil 0.5ug/kg and cisatracurium 0.15mg/kg. Maintenance of anesthesia was performed with infusion of propofol 10mg/ml, 4mg/kg/h, remifentanil 50ug/ml, 0.2ug/kg/min. To ensure adequate depth of anesthesia, response entropy indexes were kept between 40 and 60 during the whole anesthesia period by adjusting the Infusion pump speed of sufentanil and propofol.
After systemic anesthesia, In the group III and Ⅳ, the probe was transversely placed at the lateral level of the umbilicus. Using in-plane technique, the needle was advanced until the posterior aspect of the rectus muscle is penetrated. No blood and no gas were drawn back, furthermore, A small volume of saline(<2ml) was initially injected to ensure that the needle tip was correctly positioned. At present, the needle located between the posterior rectus muscle and posterior sheath, 20 ml of 0.5% ropivacaine was injected bilaterally (Figure 1).
In particular, the groupⅡand group Ⅳ received intravenous infusion of 1 mg butorphanol 30 minutes before the end of surgery. The groupⅠand groupⅢ received intravenous infusion of 10 ug sufentanil 30 minutes before the end of surgery.
Vital signs such as blood pressure, heart rate, oxygen saturation electrocardiogram were recorded during the operation. Operation time, hemorrhage volume and the consumption of remifentanil and propofol were also taken notes.
PCIA with a bolus dose of 2ug sufentanil, a lock-out interval of 15 minutes and the maximum dose of 2ug/h was used for routine analgesia in the groupⅠ and groupⅢ. In the groupⅡand group Ⅳ, all patients received butorphanol PCIA set at a background rate of 170ug/h and a demand dose of 170ug every 15 min as rescue analgesia for postoperative pain management. During a preoperative visit, patients were adequately informed about the concept of VAS and trained how to use PCIA.
All patients were operated by the same experienced anesthesiologist, who specialized in ultrasound-guided regional anesthesia, blinded to the grouping and did not participate in postoperative data collection.
Measurements
Primary outcomes: In both groups, a blinded investigator who was not involved in patient recruitment or anesthesia procedure recorded the incision and visceral pain using a 10-cm visual analog scale (0cm=no pain; 10cm=worst pain) at 2, 6, 12, and 24 hours after the operation;postoperative nausea and vomiting (PONV), somnolence, constipation, uroschesis, pruritus, and respiratory depression were assessed by a blinded observer separately. 1 mg butorphanol was administered intravenously as rescue analgesia in patients with VAS>3. Secondary outcome: The blinded observer recorded the doses of butorphanol, opioids, and pressing times of PCIA.
Statistical analyses
Statistical analysis was performed using IBM SPSS 21. Date in every group were expressed with mean±SD or frequency. Analysis of variance is used for measurement data groups, count data groups were analyzed using chi-square test. P<0.05 was considered statistically significant. Sample size calculation was based on α=0.05,β=0.2(power=80%), lost follow-up rate=10%.