Cite as: Blessing M, Krakowski JC, Chura M, et al. Literature review - August 2025. ASRA Pain Medicine News 2025;50. https://doi.org/10.52211/asra080125.014.

Literature Review

Acute Pain

A Comparison of the Lateral Approach (Paramedian) Versus the Modified Lateral Approach (Modified Paramedian) in Spinal Anesthesia: Evaluating Ease of Procedure and Patient Satisfaction in Urological Surgeries; A Triple-Blind Randomized Clinical Trial

Kiaei MM, Sangi S, Aligholizadeh M, et al. Anesth Pain Med 2025;15(3):e161542. https://doi.org/10.5812/aapm-161542

Summary by Marcelle Blessing, MD

Introduction: Spinal anesthesia is associated with high patient satisfaction and a favorable postoperative recovery from urologic surgery. However, technical difficulties may be encountered with either a midline or traditional paramedian approach. The authors investigated whether a modified paramedian approach was superior to a traditional paramedian approach.

 Methods: The traditional paramedian approach (P) was compared to a modified paramedian approach (MP) for spinal anesthesia (SA) in a triple-blind randomized clinical trial in patients undergoing urologic procedures. The P group for SA used a needle entry point 1 cm lateral and caudal to the spinous process with a 10-15^o angle cephalad and medial, while for the MP group, the needle was inserted 2-3 cm lateral and caudal and directed at a 30-45^o angle cephalad and medial. The two groups were compared for both patient satisfaction and procedural difficulty.

Results: A total of 112 patients for urological procedures were enrolled in the study and randomized into two groups. The results indicated that the modified paramedian group demonstrated superior performance in terms of success on the first attempt (P = 0.006), reduced need for repositioning (P = 0.038), and fewer repeated attempts (P = 0.017). Additionally, patient satisfaction scores were significantly higher in the modified paramedian group (P = 0.001). Multivariate regression confirmed age and body mass index as independent predictors of procedural difficulty (P < 0.05).

Key Point: The modified paramedian approach to spinal anesthesia described by the authors resulted in a shorter procedure time with fewer needle passes and higher patient satisfaction than the traditional paramedian approach.

Comparison of Adductor Canal Block Before Versus After Total Knee Arthroplasty in Terms of Pain, Stress, and Functional Outcomes: A Double-Blinded Randomized Controlled Trial

Wang Q, Hu J, Chen C, et al. J Bone Joint Surg Am 2025;107(8):796-804. https://doi.org/10.2106/JBJS.24.00679

Summary by James C. Krakowski, MD, FASA

Introduction: Total knee arthroplasty (TKA) is associated with significant postoperative pain, making optimal regional anesthesia strategies essential. While the adductor canal block (ACB) is widely used, the ideal timing of its administration remains uncertain.

Methods: In a double-blind, randomized controlled trial, 100 patients undergoing primary unilateral TKA were assigned to receive an ACB either 30 minutes preoperatively or postoperatively in the post-anesthesia care unit. All patients received general anesthesia and periarticular infiltration. ACB was administered using ropivacaine with epinephrine, and sham saline injections were used to maintain blinding. The primary outcome was postoperative morphine consumption. Secondary outcomes included intraoperative anesthetic requirements, rescue analgesia timing, pain scores, cortisol and ACTH levels, knee range of motion, time to discharge, and chronic pain incidence at 3 months.

Results: Preoperative ACB significantly reduced 24-hour morphine consumption (8.0 ± 6.3 mg vs. 12.0 ± 6.5 mg; p = 0.001) and total morphine use (12.3 ± 7.4 mg vs. 17.4 ± 9.1 mg; p = 0.002). It delayed the time first to rescue analgesia (16.3 ± 6.9 h vs. 12.6 ± 5.5 h; p = 0.030), reduced intraoperative opioid use and hypertensive episodes, and improved early postoperative pain scores and range of motion. The incidence of chronic pain at 3 months was lower with preoperative ACB. No significant differences were observed in ambulation, discharge timing, or complications.

Key Point: Preoperative ACB may reduce opioid use and provide superior analgesia while attenuating the perioperative stress response and chronic pain incidence at 3 months compared to postoperative ACB in patients undergoing TKA.

Evaluation of AI-based Nerve Segmentation on Ultrasound: Relevance of Standard Metrics in the Clinical Setting

Delvaux BV, Maupain O, Giral T, et al. Br J Anaesth 2025;134(5):1497-1502. https://doi.org/10.1016/j.bja.2024.12.040

Summary by Marcelle Blessing, MD

Introduction: Nerve segmentation is an early clinical application of artificial intelligence (AI) to ultrasound-guided regional anesthesia (UGRA). It has the potential to support the acquisition of optimal ultrasound images of nerves and to enhance learning and clinical practice. It also has the potential to improve the safety and efficacy of UGRA.

Methods: cNerve™ is a deep learning segmentation tool on GE Healthcare’s Venue™ ultrasound systems that highlights nerves of the interscalene and supraclavicular-level brachial plexus, femoral, and popliteal-level sciatic block regions. Expert anaesthesiologists then subjectively rated the overall segmentation quality of cNerve™ on ultrasound cine loop sequences using a 1-5 Likert scale (1, poor; 5, excellent). Sequences rated 5 were selected for objective assessments of pixel overlap of AI nerve segmentation versus expert nerve annotation, using the Intersection over Union (IoU) and Dice similarity coefficient metrics.

Results: A total of 173 still image frames were analyzed. The median IoU for nerves was 0.49, and the median Dice similarity coefficient was 0.65, indicating variable performance based on objective metrics despite subjective clinical evaluations rating the artificial intelligence-generated nerve segmentation as excellent.

Key Point: Even with subjective clinical evaluations rating the AI-generated nerve segmentation as excellent, there were variable objective metric scores. For now, subjective evaluation is needed in addition to AI tools in the clinical setting. Further work is required to bridge the gap between the technology and clinical applications.

Chronic Pain

Spinal Cord Stimulation Explanation and Chronic Pain: A Systematic Review and Technology Recommendations

Wahezi S, Yener U, Tahereh Naeimi T, et al. Pain Physician 2025;27(3):207-16.

Summary by Mamta Chura, MD

Introduction: Spinal cord stimulation (SCS) is an important modality in the management of chronic, intractable pain, but may require explanation despite excellent results. Therefore, concerns have arisen regarding the long-term efficacy of SCS. This systematic review seeks to clarify the rates and causes of SCS explanation, therefore providing insight into device performance and informing future technological refinements.

Methods: A systematic review of the literature was conducted from 1984 to 2024, utilizing the PubMed, Cochrane Library, and Web of Science databases. This review did not target a specific patient population for SCS. The initial search yielded 719 publications, 72 of which were assessed for eligibility, and 25 studies were ultimately included in the analysis. The primary outcome was the pooled SCS explanation rate, and secondary outcomes included the underlying reasons for explanations (ie, loss of therapeutic efficacy, device-related complications, and infections) as well as the associated economic burden related to device removal and revision procedures.

Results: Among 13,026 patients, 1,882 underwent device explantation, corresponding to a pooled explantation rate of 9.82%. The predominant reason cited was loss of therapeutic efficacy (38%), followed by lead-related complications (15%) and infection (14%). Notably, most explants occurred within the first postoperative year. Reported explanation rates across studies ranged from 1.8% to 38%.

Key Point: Spinal cord stimulation is associated with an explantation rate approaching 10%. This highlights the critical need for more rigorous patient selection, the need for enhanced device durability, and continued innovation in neuromodulation.

Pharmacotherapy and Non-Invasive Neuromodulation for Neuropathic Pain: A Systematic Review and Meta-Analysis.

Soliman N, Moisset X, Ferraro MC, et al. Lancet Neurol 2025;24(5):413-28. https://doi.org/10.1016/S1474-4422(25)00068-7

Summary by Vandana Sharma, MD, FASA

Introduction: The last recommendations for treatment of neuropathic pain were published in 2015 by the special interest group on neuropathic pain of the International Association for the Study of Pain. This is an updated systematic review and meta-analysis summarizing new evidence based on randomized controlled trials.

Methods: A clinical database search was conducted for randomized, double-blind, placebo-controlled trials evaluating pharmacological and non-invasive neuromodulation interventions for neuropathic pain since January 2013. Trials with mixed pain etiology and non-specific pain conditions were excluded. The primary efficacy outcome was 30%-50% pain reduction. Recommendations were based on evidence of efficacy, cost, and adverse effects, and the risk of bias was estimated.

Results: 313 studies out of 10,685 were included, with a total of 48,789 adult participants. The most evaluated drugs were α2δ-ligands, tricyclic antidepressants (TCA), serotonin–norepinephrine reuptake inhibitors (SNRI), and opioids. In neuromodulation studies, repetitive transcranial magnetic stimulation (rTMS) was the most studied, followed by transcranial direct current stimulation, motor cortex stimulation, peripheral nerve stimulation, transcutaneous electrical nerve stimulation, and spinal cord stimulation. Strong recommendations were made for use of TCAs, α2δ-ligands, and SNRIs as first-line treatments; a weak recommendation for capsaicin 8% patches, capsaicin cream, and lidocaine 5% plasters as second-line recommendations; and a weak recommendation for BTX-A, rTMS, and opioids as third-line treatments for neuropathic pain.

Key Point: Treatment outcomes for neuropathic pain have only modestly changed in a decade, while the efficacy of available interventions is modest.

Buprenorphine, Pain, and Opioid Use in Patients Taking High-Dose Long-Term Opioids: A Randomized Clinical Trial

Becker WC, Seal KH, Nelson DB, et al. JAMA Intern Med 2025;185(4):372-81. https://doi.org/10.1001/jamainternmed.2024.8361 

Summary by Howard Meng, MD, FRCPC

Introduction: Guidelines recommend tapering of long-term opioids for pain; however, strategies are limited. The use of buprenorphine, which is commonly used in patients with opioid use disorder (OUD), has emerged as a potential option to discontinue full agonist opioids in patients on long-term opioid therapy for pain without OUD.

Methods: This was a pragmatic, multisite RCT. Participants were primary care patients with moderate to severe pain on long-term opioid therapy. Inclusion criteria were 1) pain nearly every day for 6 months or more with a Pain, Enjoyment of Life, and General Activity 3-item score of 5 or more, and 2) opioid analgesics for >3 consecutive months with >70 morphine milligram equivalents. The primary and secondary outcomes were Brief Pain Inventory (BPI) and opioid dose, respectively, at 12 months.

Results: A total of 207 participants were included with 104 randomized to the buprenorphine option arm. Participants in the buprenorphine option arm (including 27/104 that switched to buprenorphine) demonstrated improvement in BPI from 6.8 (1.5) to 6.1 (1.9; adjusted mean difference [AMD], -0.59; 95% CI, -0.89 to -0.29) and from 6.8 (1.6) to 6.3 (1.7; AMD, -0/50; 95% CI, -0.81 to 0.20) in the no option arm (between group AMD, -0.09; 95% CI, -0.52 to 0.34). There were significant opioid use reductions in both arms, but no difference between arms.

Key Point: There was no difference between the buprenorphine option and no option arms for pain and opioid use at 12 months. The proportion of participants who switched to buprenorphine was low.