Patients
This study was approved by the Hospital Ethics Committee of the First People’s Hospital of Lianyungang (KY-20210423006) and written consent was obtained after informing the participants about the nature, scope and risks related to the study. The study was also registered with Chinese Clinical Trials Registry (ChiCTR2100046470). Patients of either sex, with Society of Anesthesiologists (ASA) I or II, between 18 and 65 years of age scheduled for elective arthroscopic shoulder surgery undergoing general anesthesia were eligible. The exclusion criteria were as followings: refused to receive IBPB, body mass index > 30 kg/m2, history of severe cardiovascular and respiratory disease, renal or hepatic failure, uncontrolled diabetes, allergy to any of the study drug, and contraindications to brachial plexus block (coagulopathy or local infection).
Study Design and Randomization
A statistician who was not involved in the study conducted the randomization of patients into group R (ropivacaine administration) or group DR (dexmedetomidine and ropivacaine administration) on a 1:1 ratio using a computer-generated random number table. The information regarding group assignment was placed in an opaque sealed envelope. After the patient entering into the operation room and prior to the induction of anesthesia, the numbered envelope was opened and the card inside determined into which group the patient was placed.
In Group R; patients received IBPB using 0.25% ropivacaine15 ml. Group RD; patients received IBPB using 0.25% ropivacaine and 0.5 µg/kg dexmedetomidine 15 ml. The anesthetic solutions for IBPB were prepared by an anesthesiology nurse who was not involved in the study. The anesthesiologist performing the block and observing the patient was blinded to the treatment group. Data collection was done by the same anesthesiologist who was unaware of the group allocation.
Procedure of anesthesia
None of the patients were premedicated. After entering the operation room, the patients received routine electrocardiogram (ECG), pulse oxygen saturation (SpO2), blood pressure (BP), heart rate (HR), and bispectral index (BIS) monitoring. A 20-gauge cannula was inserted into the dorsum of the patient’s hand and connected to a T-connector for drug administration; Ringer lactate was infused at a rate of 4–6 ml/min. General anesthesia was standardized for all patients in both groups. Patients were preoxygenated with 100% oxygen for 3 minutes, followed sufentanil 0.5 µg/kg, propofol 2 mg/kg was intravenously administered and cisatracurium 0.2 mg/kg was given to facilitate tracheal intubation. Anesthesia was maintained with sevoflurane/O2 /air mixture to keep BIS values between 40 and 60, muscle relaxation was provided using IV cisatracurium. All surgical interventions were performed by the same surgical team.
Procedure of IBPB
The patient was in the supine position with the head slightly turned away from the operative side. Skin was prepared using antiseptic solution, and transducer was wrapped in a sterile cover. A 6-13-MHz high-frequency linear probe of the ultrasound (Philips CX50, Philips Ultrasound, Inc., Bothell, WA, USA) was used to identify the C5-C6-C7 nerve roots of the brachial plexus, which appeared as three beads that were approximately vertically aligned between the anterior and middle scalene muscles on the ultrasound image.17 Then a 21G*100mm insulated needle (UniPlex NanoLine, Pajunk, Geisingen, Germany) was advanced via the lateral-to-medial approach to target the nerve root, and then ropivacaine alone or ropivacaine with dexmedetomidine was injected around the nerve root. All nerve blocks were performed by anesthesiologists who were experts in performance of ultrasound-guided nerve blocks. After completion of the nerve block and reversal of neuromuscular blockade effect, the trachea will be extubated. Then the patient was transferred to the post-anesthesia care unit (PACU).
Postoperative Pain Control
All patients received intravenous sufentanil with an intravenous patient-controlled analgesia (PCA) system at the end of surgery. The mode of PCA was a bolus of sufentanil 0.05µg/kg, a lockout time of 15 min, and a continuous infusion of sufentanil 0.04µg/kg/h (total regimen 2µg/kg/100 ml). The patients were taught to push the button of the PCA system to receive a bolus of sufentanil each time pain occurred. If the visual analogue scale (VAS) score was ≥ 4, 40 mg parecoxib sodium was injected intravenously as a rescue analgesic.
Studied Variables
Duration of analgesia was defined as the time interval between the completion of IBPB and the time when the patient complained of shoulder pain, and was noted every 30 min since the completion of the IBPB for 4 hours.
The VAS (0–10) pain score (VAS; where 0 = no pain and 10 = worst imaginable pain) was assessed at 2, 4, 6, 8, 10, 12 and 24 h after surgery.
Frequency of PCA pressed was recorded at T0-4、T4-8、T8-12、T12-16、T16-20、T20-24 h postoperatively. The first time of PCA pressed and the total 24h sufentanil consumption were also recorded.
Patient satisfaction with analgesia quality 24 h post-surgery (Number ricrating scale, NRS 1–5; 1, very dissatisfied; 2, dissatisfied; 3, slightly dissatisfied; 4, quite satisfied; 5, completely satisfied) was recorded.
The primary outcome measure in this study was the duration of analgesia. The secondary outcome measures included VAS pain score, frequency of PCA pressed, first time of PCA pressed, total 24h sufentanil consumption, and patient satisfaction with analgesia quality .
Statistical analysis
The sample size was calculated on the basis of a pilot study taking a mean value of 8.0 h and SD 1.78 h for the duration of postoperative analgesia in 10 patients who received IBPB with ropivacaine. A 20% difference in the duration of the postoperative analgesia was considered a clinically relevant difference. For a 2-group t test with α = 0.05, β = 0.2 and 2-sided significance level, we required 21 patients in each group. A total of 50 patients were recruited in the study to compensate for possible dropouts.
Statistic tests were performed using SPSS 16.0 for windows (SPSS 16, Chicago, IL, USA). Continuous numerical data were expressed as mean and standard deviation, or median and interquartile range. Categorical data were expressed as frequencies and percentages. Normally distributed numerical data between groups were analyzed using the independent 2-sample t-test. Skewed data between groups were analyzed using the Mann–Whitney U-test. Categorical variables were analyzed using the Fisher’s exact test or the Pearson’s Chi-square test as applicable. All tests were two-tailed. P < 0.05 was considered statistically significant.