Postoperative pain following lower abdominal surgeries is often moderate to severe and, if inadequately managed, can lead to delayed ambulation, prolonged hospitalization, and increased postoperative morbidity. Conventional systemic analgesics such as opioids and non-steroidal anti-inflammatory drugs (NSAIDs), although effective, are frequently associated with adverse effects including nausea, vomiting, sedation, respiratory depression, and gastrointestinal complications [1,2]. These limitations have prompted increasing interest in regional analgesic techniques as part of multimodal postoperative pain management. The transversus abdominis plane (TAP) block is a regional anesthesia technique that provides effective somatic analgesia of the anterior abdominal wall by blocking the thoracolumbar nerves (T6–L1) within the fascial plane between the internal oblique and transversus abdominis muscles. Since its initial description by Rafi, the TAP block has gained widespread acceptance, particularly after the advent of ultrasound guidance, which has significantly improved block accuracy, success rates, and safety [3,4]. Ultrasound-guided TAP block has been shown to reduce postoperative pain scores and opioid consumption following various lower abdominal procedures [5,6]. Bupivacaine and ropivacaine are long-acting amide local anesthetics commonly used for TAP block. While bupivacaine provides effective and prolonged analgesia, its clinical use is limited by concerns regarding cardiotoxicity and neurotoxicity, especially when administered in larger volumes [7]. Ropivacaine, the pure S-enantiomer, has a more favorable safety profile with reduced cardiotoxicity and greater sensory-motor differentiation, making it an attractive alternative for regional blocks [8]. Several studies have evaluated these agents in different surgical settings, reporting either comparable or superior analgesic efficacy with ropivacaine [9–11]. However, despite increasing use of ultrasound-guided TAP block, there is no clear consensus regarding the optimal local anesthetic agent for achieving prolonged postoperative analgesia with minimal adverse effects. Therefore, the present randomized double-blind study was undertaken to compare the analgesic efficacy of ropivacaine and bupivacaine when used in ultrasound-guided TAP block for postoperative pain control in patients undergoing elective lower abdominal surgeries.

Study Design and Setting This prospective, randomized, double-blind clinical trial was conducted at a tertiary care teaching hospital after obtaining approval from the Institutional Ethics Committee. Written informed consent was obtained from all participants prior to enrollment. Study Population A total of 100 patients of either sex, aged 18–65 years, belonging to ASA physical status I and II, scheduled for elective lower abdominal surgeries under spinal or general anesthesia were included. Inclusion Criteria • Age between 18 and 65 years • ASA physical status I or II • Elective lower abdominal surgeries • Willingness to participate and provide informed consent Exclusion Criteria • Refusal to participate • Known allergy to amide local anesthetics • Local infection at injection site • Coagulopathy or bleeding disorders • Pregnancy • Chronic pain conditions or opioid dependence Randomization and Blinding Patients were randomized into two equal groups (n = 50 each) using a computer-generated randomization sequence. Allocation concealment was ensured using sealed opaque envelopes. Both patients and outcome assessors were blinded to group allocation. Intervention At the completion of surgery, an ultrasound-guided TAP block was administered under aseptic precautions using a high-frequency linear ultrasound probe. • Group R (Ropivacaine group): Received 15 mL of 0.25% ropivacaine • Group B (Bupivacaine group): Received 15 mL of 0.25% bupivacaine The block was performed bilaterally on the surgical incision. Outcome Measures • Primary outcome: Postoperative pain intensity assessed using Numeric Rating Scale (NRS) • Secondary outcomes: Duration of analgesia, total rescue analgesic consumption in 24 hours, patient satisfaction score, and adverse effects Rescue analgesia was administered when NRS > 3 using intravenous diclofenac. Statistical Analysis Data were analyzed using SPSS software. Continuous variables were expressed as mean ± SD and compared using Student’s t-test. Categorical variables were analyzed using Chi-square or Fisher’s exact test. A p-value < 0.05 was considered statistically significant. Figure 1. Consort diagram of the study

A total of 100 patients completed the study without dropouts during the study period and their demographic and clinical data were as below. Table 1: Demographic Characteristics Parameter Group R (n=50) Group B (n=50) p-value Age (years) 37.7 ± 11.3 36.8 ± 11.7 0.71 Weight (kg) 67.2 ± 6.2 65.7 ± 7.0 0.26 ASA I/II 37/13 38/12 1.00 Table 1 presents the demographic characteristics of the study participants in both groups. The mean age of patients in Group R was 37.7 ± 11.3 years, while that in Group B was 36.8 ± 11.7 years, with no statistically significant difference between the groups (p = 0.71). Similarly, the mean body weight was comparable between Group R (67.2 ± 6.2 kg) and Group B (65.7 ± 7.0 kg), and the difference was not statistically significant (p = 0.26). The distribution of ASA physical status was also similar in both groups, with 37 patients classified as ASA I and 13 as ASA II in Group R, compared to 38 ASA I and 12 ASA II patients in Group B (p = 1.00). Overall, the two groups were well matched with respect to baseline demographic and clinical characteristics, indicating successful randomization and comparability prior to intervention. Table 2: Analgesic Outcomes Parameter Group R Group B p-value Duration of analgesia (hours) 11.8 ± 2.4 8.3 ± 1.9 <0.001 Mean NRS at 6 hours 2.3 ± 0.8 3.6 ± 1.0 <0.001 Rescue analgesic doses (24 h) 1.2 ± 0.6 2.4 ± 0.8 <0.001 Table 2 summarizes the postoperative analgesic outcomes in both study groups. The mean duration of analgesia was significantly longer in Group R (11.8 ± 2.4 hours) compared to Group B (8.3 ± 1.9 hours), and this difference was statistically highly significant (p < 0.001). Pain intensity assessed at 6 hours postoperatively using the Numeric Rating Scale (NRS) was significantly lower in Group R (2.3 ± 0.8) than in Group B (3.6 ± 1.0), indicating superior analgesic efficacy of ropivacaine (p < 0.001). Furthermore, the total number of rescue analgesic doses required within the first 24 hours postoperatively was significantly reduced in Group R (1.2 ± 0.6) compared to Group B (2.4 ± 0.8), with the difference being statistically significant (p < 0.001). Overall, these findings demonstrate that ropivacaine provided more effective and prolonged postoperative analgesia with a reduced requirement for supplemental analgesics compared to bupivacaine. Table 3: Comparison of Patient Satisfaction Scores Satisfaction Level Group R n (%) Group B n (%) p-value Totally dissatisfied 1 (2.0) 5 (10.0) <0.01 Moderately dissatisfied 4 (8.0) 12 (24.0) Reasonably satisfied 15 (30.0) 21 (42.0) Totally satisfied 30 (60.0) 12 (24.0) Table 3 compares patient satisfaction scores between the two study groups using a four-point Likert scale. A markedly higher proportion of patients in Group R reported being totally satisfied with postoperative analgesia (60.0%) compared to Group B (24.0%). Conversely, dissatisfaction was more frequently observed in Group B, with 10.0% of patients being totally dissatisfied and 24.0% moderately dissatisfied, compared to 2.0% and 8.0%, respectively, in Group R. The proportion of patients who were reasonably satisfied was comparable between the groups, though slightly higher in Group B (42.0%) than in Group R (30.0%). Overall, the distribution of satisfaction scores differed significantly between the two groups, with patient satisfaction being significantly higher in the ropivacaine group than in the bupivacaine group (p < 0.01), indicating superior patient-perceived quality of postoperative analgesia with ropivacaine.

The present randomized double-blind study demonstrates that ultrasound-guided TAP block using ropivacaine provides superior postoperative analgesia compared to bupivacaine in patients undergoing elective lower abdominal surgeries. This superiority was reflected by significantly lower pain scores, prolonged duration of analgesia, and reduced rescue analgesic requirement. Ultrasound-guided TAP block has emerged as a reliable component of multimodal analgesia for abdominal surgeries. Its efficacy in reducing postoperative pain and opioid consumption has been consistently demonstrated across various surgical populations [3–6]. The ability to visualize anatomical planes under ultrasound guidance ensures precise deposition of local anesthetic, thereby improving block success and minimizing complications. In the present study, ropivacaine produced a significantly longer duration of analgesia compared to bupivacaine. Similar findings were reported by Sharma et al., who observed prolonged analgesia and lower analgesic requirements with 0.5% ropivacaine compared to 0.25% bupivacaine in ultrasound-guided TAP block [9]. Comparable results have also been reported in obstetric and laparoscopic procedures [10–12]. The pharmacological properties of ropivacaine may explain its superior performance. As a pure S-enantiomer, ropivacaine exhibits reduced cardiotoxicity and neurotoxicity while providing effective sensory blockade with minimal motor involvement [8]. This favorable safety profile is particularly important in TAP block, which requires relatively larger volumes of local anesthetic to achieve adequate spread. Bupivacaine, although effective, has a narrower margin of safety. Concerns regarding cardiotoxicity have limited its widespread use, especially in bilateral blocks or in patients with comorbidities [7]. The reduced need for rescue analgesics in the ropivacaine group observed in the present study highlights its opioid-sparing effect, which is clinically significant in enhancing postoperative recovery and patient satisfaction. The higher satisfaction observed in the ropivacaine group can be attributed to its prolonged duration of analgesia and lower postoperative pain scores, which resulted in reduced need for rescue analgesics. Effective pain control facilitates early mobilization, improved sleep quality, and enhanced postoperative well-being, all of which contribute to higher patient satisfaction. Similar findings have been reported in previous studies evaluating TAP block in abdominal and obstetric surgeries. Parmar et al. demonstrated significantly higher patient and surgeon satisfaction scores in patients receiving ropivacaine compared to bupivacaine following lower segment cesarean section, which was attributed to superior analgesic efficacy and delayed requirement of rescue analgesia [11]. Sharma et al. also reported better patient satisfaction with ropivacaine in ultrasound-guided TAP block for lower abdominal surgeries [9]. The findings of this study are also consistent with previous comparative trials conducted in cesarean section and laparoscopic surgeries, where ropivacaine was associated with lower pain scores and longer analgesic duration [11–14]. Importantly, no significant hemodynamic instability or adverse effects were observed in either group, underscoring the safety of ultrasound-guided TAP block when performed correctly. The limitations of this study include its single-center design and lack of long-term follow-up for chronic pain outcomes. Plasma concentrations of local anesthetics were not measured. Future multicenter trials with larger sample sizes and extended follow-up may provide further clarity regarding optimal dosing strategies.

Ultrasound-guided transversus abdominis plane block is a safe and effective technique for postoperative analgesia following elective lower abdominal surgeries. Ropivacaine provides longer-lasting analgesia, lower pain scores, and reduced requirement for rescue analgesics compared to bupivacaine. Given its favorable safety profile and superior analgesic efficacy, ropivacaine may be preferred for ultrasound-guided TAP block as part of a multimodal postoperative pain management strategy.

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