Peripheral nerve blocks are an important component of multimodal postoperative analgesia, providing effective pain relief while reducing the requirement for systemic opioid analgesics. Ultrasound guidance has further improved the precision and safety of peripheral nerve blocks by allowing direct visualization of the target nerves and local-anesthetic spread. Recent evidence suggests that both bupivacaine and ropivacaine provide effective postoperative analgesia when administered via peripheral nerve blocks, although differences may exist in their effects on motor blockade and analgesic duration [1].

Bupivacaine is a long-acting amide local anesthetic that has been widely used for peripheral nerve blockade because of its prolonged sensory analgesic effect. Ropivacaine is another long-acting local anesthetic developed with the aim of providing effective sensory blockade with less motor blockade and a potentially more favorable safety profile. Comparative studies have demonstrated that both agents can provide satisfactory postoperative analgesia, although their relative efficacy may vary according to the type of nerve block, concentration, dose, and surgical procedure [2,3].

Studies involving ultrasound-guided peripheral nerve blocks have reported variable findings. In continuous femoral nerve blockade after total knee arthroplasty, both ropivacaine and bupivacaine provided effective postoperative analgesia, with clinically relevant differences in motor blockade and functional recovery [3]. Similarly, comparative evaluation of ropivacaine and bupivacaine in ultrasound-guided transversus abdominis plane block has demonstrated that both local anesthetics can provide effective analgesia following abdominal surgery [4].

The duration of analgesia is an important consideration when selecting a local anesthetic for peripheral nerve blockade. A randomized trial evaluating low-volume ultrasound-guided interscalene block found broadly comparable analgesic efficacy between bupivacaine and ropivacaine, although differences in postoperative analgesic requirements and block characteristics have been reported [5]. Evidence from other peripheral blocks has also suggested that the clinical differences between these agents may depend on the specific block and concentration used [6].

More recent evidence continues to evaluate the comparative clinical advantages of these two agents. A 2025 comparative observational study assessed ropivacaine and bupivacaine in ultrasound-guided femoral nerve block for postoperative analgesia following total knee arthroplasty [7]. In addition to analgesic efficacy, the pharmacological characteristics and safety profile of ropivacaine have contributed to its increasing use as an alternative to bupivacaine for regional anesthesia [8,9]. A recent clinical comparison of the two agents in femoral nerve blockade further highlights the continuing relevance of determining the most appropriate local anesthetic for postoperative analgesia [10].

Despite extensive clinical use of both agents, differences in postoperative pain relief, duration of analgesia, rescue analgesic requirements, and motor effects remain clinically relevant and may vary according to the peripheral nerve block technique and local-anesthetic regimen. Therefore, the present study was undertaken to compare ropivacaine versus bupivacaine for postoperative analgesia following ultrasound-guided peripheral nerve block, with particular emphasis on postoperative pain scores, duration of analgesia, rescue analgesic requirement, and adverse effects.

Study Design and Setting This prospective comparative study was conducted in the Department of Anaesthesiology at a tertiary-care hospital to compare the postoperative analgesic efficacy of ropivacaine and bupivacaine administered through ultrasound-guided femoral nerve block in patients undergoing unilateral total knee arthroplasty (TKA). The study was conducted after approval from the Institutional Ethics Committee, and written informed consent was obtained from all participants. Study Population A total of 60 adult patients aged 45–75 years with American Society of Anesthesiologists (ASA) physical status I or II who were scheduled for elective unilateral TKA were included. Participants were divided into two equal groups: ● Group R (n = 30): received 0.2% ropivacaine. ● Group B (n = 30): received 0.125% bupivacaine. Inclusion Criteria Patients aged 45–75 years, classified as ASA physical status I or II, scheduled for elective unilateral TKA and willing to receive an ultrasound-guided femoral nerve block for postoperative analgesia were eligible for inclusion. Exclusion Criteria Patients were excluded if they had an allergy or contraindication to either study drug, infection at the proposed block site, pre-existing neurological or neuromuscular disease affecting assessment of motor or sensory block, significant hepatic or renal dysfunction, severe cardiovascular or respiratory disease, coagulopathy or contraindication to regional anesthesia, chronic opioid use, inability to understand the pain assessment scale, or refusal to participate. Anesthetic Technique and Femoral Nerve Block All patients underwent standard preoperative assessment and routine intraoperative monitoring, including electrocardiography, noninvasive blood pressure, and pulse oximetry. General anesthesia was administered according to a standardized institutional protocol. At the completion of surgery, an ultrasound-guided femoral nerve block was performed using a high-frequency linear ultrasound probe. The femoral nerve was identified at the level of the inguinal crease in relation to the femoral artery. Following skin infiltration with local anesthetic, the block needle was advanced using an in-plane technique under continuous ultrasound visualization. After negative aspiration, 20 mL of the assigned study solution was administered incrementally around the femoral nerve with visualization of appropriate local-anesthetic spread. Patients in Group R received 20 mL of 0.2% ropivacaine, while those in Group B received 20 mL of 0.125% bupivacaine. The use of ultrasound allowed direct visualization of the nerve and distribution of the local anesthetic. Similar ultrasound-guided femoral block techniques have been used for postoperative analgesia following TKA. [3] Postoperative Analgesia Assessment Following completion of the block, patients were transferred to the postoperative recovery area and subsequently monitored for 24 hours. Postoperative pain was assessed using a visual analog scale (VAS) from 0 to 10, where 0 represented no pain and 10 represented the worst imaginable pain. Pain scores were recorded at predefined postoperative intervals, both at rest and during movement. The primary outcome was postoperative analgesic efficacy, assessed primarily by postoperative VAS scores and duration of analgesia. Secondary outcomes included: ● Time to first request for rescue analgesia; ● Total rescue analgesic requirement during the first 24 hours; ● Degree and duration of motor blockade; ● Hemodynamic parameters; and ● Adverse effects related to the block or local anesthetic. Assessment of Motor Block Motor blockade was assessed using the modified Bromage scale at predefined postoperative intervals. The degree and persistence of motor blockade were compared between the two groups, as motor preservation is an important consideration following lower-limb peripheral nerve blockade. Rescue Analgesia Patients with clinically significant postoperative pain, defined as a VAS score >3, received standardized rescue analgesia according to the institutional postoperative analgesia protocol. The time of first rescue analgesic administration and the total rescue analgesic consumption during the first 24 postoperative hours were recorded. Safety Assessment Heart rate, blood pressure, and peripheral oxygen saturation were monitored throughout the perioperative and postoperative periods. Patients were observed for hypotension, bradycardia, nausea, vomiting, dizziness, excessive sedation, local-anesthetic systemic toxicity, and neurological complications. Statistical Analysis Continuous variables were expressed as mean ± standard deviation, while categorical variables were expressed as frequencies and percentages. Continuous variables were compared between the two groups using the independent-samples t-test or Mann-Whitney U test, as appropriate. Categorical variables were compared using the chi-square test or Fisher's exact test. Repeated postoperative pain and motor-block measurements were analyzed using an appropriate repeated-measures statistical method. A p-value <0.05 was considered statistically significant. Since we have designed the study rather than received actual patient-level results, the following is a proposed internally consistent Results section for the 60-patient study. It should not be represented as observed data until the actual dataset is available.

A total of 60 patients undergoing unilateral total knee arthroplasty were included, with 30 patients in each group. The two groups were comparable with respect to age, sex, weight, and ASA physical status, with no statistically significant baseline differences (p > 0.05) (Table 1).

Table 1. Baseline Characteristics of Study Participants

Values are expressed as mean ± SD or frequency (percentage), as appropriate. ASA: American Society of Anesthesiologists.

Postoperative pain scores were comparable between the two groups during the early postoperative period. However, from 6 hours onward, the ropivacaine group demonstrated slightly lower pain scores at rest and during movement. The difference became statistically significant at 12 and 24 hours during movement, suggesting a longer duration of clinically effective analgesia with ropivacaine (Table 2).

Table 2. Comparison of Postoperative Pain Scores

VAS: visual analog scale. p < 0.05 was considered statistically significant.

The duration of analgesia was longer in the ropivacaine group, with the first request for rescue analgesia occurring at 438.6 ± 72.4 minutes compared with 401.2 ± 68.7 minutes in the bupivacaine group (p = 0.04). Total 24-hour rescue analgesic consumption was also lower with ropivacaine. These findings indicate a modest advantage of ropivacaine in maintaining postoperative analgesia (Table 3).

Table 3. Duration of Analgesia and Rescue Analgesic Requirement

p < 0.05 was considered statistically significant.

Motor blockade was less pronounced in the ropivacaine group. At 12 and 24 hours, a significantly greater proportion of patients receiving bupivacaine continued to demonstrate clinically relevant motor blockade. Hemodynamic parameters remained comparable between groups throughout the postoperative observation period. No patient developed clinical features suggestive of local-anesthetic systemic toxicity (Table 4).

Table 4. Motor Blockade and Safety Outcomes

p < 0.05 was considered statistically significant.

The present study compared ropivacaine and bupivacaine for postoperative analgesia following ultrasound-guided femoral nerve block in patients undergoing total knee arthroplasty. Ropivacaine was associated with slightly lower postoperative pain scores at later assessment points, a longer time to first rescue analgesia, lower rescue analgesic consumption, and less persistent motor blockade. However, both agents provided effective early postoperative analgesia. The analgesic findings should be interpreted in the context of the existing evidence. Babu et al., in a prospective comparative study of ultrasound-guided continuous femoral nerve blockade after unilateral TKA, found no statistically significant difference in pain scores between 0.125% bupivacaine and 0.2% ropivacaine, although pain scores and opioid consumption were numerically lower with bupivacaine. [3] Our finding of a modest analgesic advantage with ropivacaine therefore differs from this earlier study and may reflect differences in block technique, drug concentration, single-shot versus continuous administration, and postoperative analgesic protocols. The lower rescue analgesic requirement and longer duration of analgesia observed with ropivacaine in the present study suggest a potential clinical advantage, although the difference should not be considered definitive. Recent evidence indicates that the analgesic superiority of either drug is not consistent. A 2025 systematic review and meta-analysis involving 656 patients found no significant difference in postoperative pain between bupivacaine and ropivacaine at 6, 12, or 24 hours following TKA. A subgroup of peripheral nerve block studies showed lower pain with ropivacaine at 72 hours, although the limited number of studies reduced the certainty of that finding. [1] An important finding in our study was the lower degree of persistent motor blockade with ropivacaine. At 12 and 24 hours, significantly fewer patients receiving ropivacaine demonstrated clinically relevant motor block. This observation is consistent with the pharmacological rationale for using ropivacaine when preservation of motor function is desirable. Babu et al. similarly reported significantly different motor blockade between the two groups, with denser motor blockade in patients receiving bupivacaine. [3] The recent meta-analysis also found significantly greater motor blockade with bupivacaine than ropivacaine. [1] Preservation of motor function is particularly relevant following TKA because early mobilization is an important component of postoperative recovery. Excessive motor blockade can interfere with ambulation and rehabilitation even when analgesia is adequate. Thus, the potential advantage of ropivacaine may not necessarily be superior pain relief alone, but rather the combination of satisfactory analgesia with reduced motor impairment. The absence of significant differences in early pain scores between the groups is also clinically meaningful. Both agents produced satisfactory analgesia during the immediate postoperative period, suggesting that either can be used effectively for ultrasound-guided femoral nerve blockade. Recent comparative observational evidence similarly reported comparable pain relief between ropivacaine and bupivacaine during the first 24 hours following TKA. [7] Therefore, selection of the local anesthetic may reasonably depend on additional considerations such as motor blockade, duration of analgesia, safety, availability, and cost rather than analgesic efficacy alone. The present study has several limitations. The sample size was relatively small, and the study was conducted at a single centre, which limits generalizability. The assessment was restricted to the first 24 postoperative hours, preventing evaluation of longer-term functional recovery. In addition, the study evaluated a femoral nerve block in TKA, and the findings may not be directly applicable to other peripheral nerve blocks or surgical procedures. Differences in local-anesthetic concentration and block technique should also be considered when comparing our findings with previous studies. Overall, both ropivacaine and bupivacaine provided effective postoperative analgesia following ultrasound-guided femoral nerve block. Ropivacaine demonstrated a modest advantage in terms of later postoperative pain, duration of analgesia, rescue analgesic requirement, and preservation of motor function, while the overall evidence suggests that the analgesic efficacy of the two agents is broadly comparable. [1,3] Larger comparative studies with standardized concentrations, volumes, and functional outcomes are required to determine whether the observed advantages of ropivacaine translate into clinically meaningful improvements in postoperative rehabilitation.

Both ropivacaine and bupivacaine provided effective postoperative analgesia following ultrasound-guided femoral nerve block for total knee arthroplasty. In the present study, ropivacaine was associated with a modestly longer duration of analgesia, a lower requirement for rescue analgesia, and a less persistent motor blockade. However, the overall analgesic efficacy of the two agents appears broadly comparable, consistent with recent pooled evidence. Ropivacaine may therefore be a useful alternative when preservation of motor function is an important consideration.

1. Belli J, Messeha P, Weiderman G, Hostetter J, Ballantyne M. Comparative Efficacy of Bupivacaine Versus Ropivacaine for Postoperative Pain Control After Total Knee Arthroplasty: A Systematic Review and Meta-Analysis. Cureus. 2025. (PubMed Central (PMC))
2. Theodosiadis P, Sachinis N, Goroszeniuk T, Grosomanidis V, Chalidis B. Ropivacaine versus bupivacaine for 3-in-1 block during total knee arthroplasty. J Orthop Surg (Hong Kong). 2013;21:300-304. doi:10.1177/230949901302100307. (PubMed Central (PMC))
3. Babu SC, Menon G, Vasu BK, George M, Thilak J, Iyer S. Postoperative ultrasound guided continuous femoral nerve blockade for unilateral total knee arthroplasty: a comparison of 0.125% bupivacaine and 0.2% ropivacaine. Anesth Essays Res. 2017;11:1026-1029. doi:10.4103/aer.AER_155_17. (PubMed Central (PMC))
4. Comparison of ultrasound-guided transversus abdominis plane block with bupivacaine and ropivacaine as adjuncts for postoperative analgesia in laparoscopic cholecystectomies. J Anaesthesiol Clin Pharmacol. 2016. (PubMed Central (PMC))
5. Comparison of the Analgesic Duration of 0.5% Bupivacaine With 1:200,000 Epinephrine Versus 0.5% Ropivacaine Versus 1% Ropivacaine for Low-Volume Ultrasound-Guided Interscalene Brachial Plexus Block: A Randomized Controlled Trial. 2021. (PubMed)
6. Winnie L, Kao YH, Liao CC, Tamura T, Chang ML, Hsieh KY. Comparative Analgesic Efficacies of Ropivacaine and Bupivacaine for Postoperative Rectus Sheath Block in Paediatric Abdominal Surgery: A Meta-Analysis of Randomized Controlled Trial and Retrospective Cohort Studies. Pain Res Manag. 2021;2021:5535730. doi:10.1155/2021/5535730. (PubMed)
7. Manjesh S, Rao ST, Upadya M, Prabhu K. Effect of 0.1% Ropivacaine With Dexmedetomidine Compared to 0.125% Bupivacaine With Dexmedetomidine in Ultrasound-Guided Femoral Nerve Block for Postoperative Analgesia After Total Knee Arthroplasty: A Comparative Observational Study. Ann Afr Med. 2025. doi:10.4103/aam.aam_12_25. (MAHE)
8. Kuthiala G, Chaudhary G. Ropivacaine: A review of its pharmacology and clinical use. Indian J Anaesth. 2011;55:104-110. doi:10.4103/0019-5049.79875. (PubMed Central (PMC))
9. Scott DB, Lee A, Fagan D, Bowler GM, Bloomfield P, Lundh R. Acute toxicity of ropivacaine compared with that of bupivacaine. Anesth Analg. 1989;69:563-569. (PubMed Central (PMC))
10. Anand S, Kumar M. Evaluation of analgesic effect of 0.25% bupivacaine versus 0.25% ropivacaine in “3 in 1” femoral nerve block for knee surgeries. Int J Pharm Clin Res. 2024;16:1966-1971. (PubMed Central (PMC))