This prospective, randomized, controlled study was conducted on 58 patients undergoing abdominoplasty, in accordance with the CONSORT guidelines,15 after obtaining the hospital ethics committee’s approval and informed written consent from all patients. The study adhered to the principles of the Declaration of Helsinki, 7th revision (2013).
Based on a previous study,6 the reduction in the mean dose of postoperative analgesic opioids was 39%. Authors considered a 25% increase in the reduced mean dose of opioids requirement postoperatively to 64% to be clinically significant. Assuming an α error of 0.05, β error of 0.1, and the power of study to be 90%, 24 patients were needed in each group to detect any clinical effect. We enrolled 29 patients in each group to accommodate for any dropout.
The inclusion criteria comprised patients undergoing abdominoplasty with rectus sheath plication and those with the American Society of Anesthesiologists (ASA) physical status (I-II).16 Exclusion criteria consisted of patients with a history of known hypersensitivity to local anesthesia, psychiatric disorders, and use of psychiatric medications, and patients refusing to participate in the study.
Patients were randomly assigned through computer-generated numbers using the random allocation software QuickCals (GraphPad Software Inc., La Jolla, CA, USA) to two groups – BG (n=29) and CG (n=29).
Preoperatively, the patients were educated on the use of the incentive spirometer and VAS to monitor their pain postoperatively (wherein 0 represented no pain and 10 indicated the worst possible pain).
The anesthesia management for all patients was the same. On arrival in the operation theater, patients were monitored using electrocardiography (ECG), non-invasive blood pressure (NIBP) measurement, and pulse oximetry. Intravenous infusion of warm Ringer’s lactate solution was initiated. All patients received general anesthesia. Midazolam 0.03 to 0.05 mg/kg was given intravenously after adequate pre-oxygenation anesthesia was induced by IV fentanyl 1 to 2 μg/kg, propofol 1.5 to 2 mg/kg, and cisatracurium 0.15 to 0.2 mg/kg. Tracheal intubation was done and the ventilator settings were adjusted to maintain the end-tidal carbon dioxide tension at 30 to 35 mmHg. Anesthesia was maintained using 1.2 Monitored Anesthesia Care (MAC) isoflurane, 40% oxygen and 60% nitrous oxide mixture, and IV cisatracurium in incremental doses. Also, incremental doses of morphine 0.01 to 0.03 mg/kg were given intraoperatively with an interval of 30 min between each dose or when needed to avoid any increase in the vital signs of >20% of basic vitals preoperatively.
Standard abdominoplasty and rectus sheath plication with or without liposuction were performed for all patients by the same experienced surgeon. The procedure was initiated with liposuction, if indicated, by infiltrating the subcutaneous abdominal layer with normal saline mixed with adrenaline, followed by the suctioning of most of the fat layer using a 2-4 mm cannula through small skin incisions.
For abdominoplasty – initially, the umbilicus was separated from the abdominal wall through a circular incision and a dissection was performed along the umbilicus stalk. Then, an incision was made horizontally at the pubic hair boundary, approximately 3-4 cm caudal to the anterior superior iliac spine on both sides. The flap was dissected cranially along the superficial fascia in a lateral direction as far as the xiphoid process and the costal arch while ensuring immediate hemostasis at all times.
Plication of the rectus sheath was carried out by doubling the fascia longitudinally to achieve a good result for the tightening of the abdominal wall. The first layer was sutured using interrupted mattress sutures whereas the second layer, which formed a sort of a mesh, was sutured using a continuous loop suture. The flap was then pulled down and the excess skin/fat layer excised. The wound was closed in three layers. Finally, the new umbilicus site was created.
By the end of the surgery – a bilateral subcostal and posterior TAPB was done to provide a sensory block for the anterior abdominal wall dermatomes from T6 to L1 in the BG group after wound closure and dressing. Ultrasound-guided block was performed using a high-frequency linear probe 7-15 MHz, a 22-gauge needle for injection, and 2 mg/kg of isobaric bupivacaine 0.25% as local anesthetic with dexamethasone 0.1 to 0.2 mg/kg to increase the duration of local anesthesia. For the subcostal TAPB, the transversus abdominis muscle was identified starting beneath the rectus abdominis muscle. The target was to visualize the fascial plane between the internal oblique and transversus abdominis muscles where 10 mL of LA was injected on each side. For the posterior TAPB, the three layers of the abdominal wall muscles (external and internal oblique as well as the transversus abdominis muscles) were visualized, and the fascial plane between the internal oblique and the transversus abdominis muscles was injected with 15 to 20 mL of LA on each side.
The use of ultrasound aids in performing the block with a clear vision of the needle tip, and also for observing the spread of the LA which allows us to avoid injuring the internal structures (intestine/vascular) and to deposit just the right amount of LA to achieve the wanted effect without the risk of dose-related toxicity.
After completing the block, isoflurane was discontinued. Neuromuscular blockade was reversed with 0.025 to 0.05 mg/kg neostigmine and 0.01 to 0.02 mg/kg atropine, followed by extubation of all patients.
In the post-anesthesia care unit (PACU), where the patients were observed and monitored for 1 h; ECG, NIBP, pulse oximetry, respiratory rate, and effort were monitored as also the VAS at rest and during movement (or with knee flexion) at 1 h (H1). After arrival to PACU, all patients received IV pethidine 50 mg when VAS ≥4.
In the ward, patients' data were recorded for 72 h postoperatively, including opioids consumption, VAS at rest and during movement (or with knee flexion) at 3 h (H3), 6 h (H6), 12 h (H12), 24 h (H24), 36 h (H36), 48 h (H48), 60 h (H60), and 72 h (H72). Also, time to first ambulation and time to first incentive spirometer when the patient was able to reach 900 mL/min were recorded.
For all the patients, the analgesic regimen consisted of IV Paracetamol 1 g every 6 h. VAS values were recorded postoperatively and once the patient had a VAS ≥4, pethidine 50 mg IV was administered with an interval not less than 3 to 4 h between each pethidine dose and the VAS recorded every 30 min until the pain improved.
Data entry and analyses were performed using the SPSS statistical package, version 27 (SPSS, Inc., Chicago, IL, USA). The data were examined for normal distribution using the Shapiro-Wilk test. For parametric data, t-test was used for mean ± SD whereas for nonparametric data, Wilcoxon signed rank test was applied for median or frequency. The statistical significance level was set at p≤0.05, post-hoc power test SPSS was also performed using G power 220.127.116.11 to determine the sample size. All calculated P values were two-tailed.