Determining the Maximum Tolerable Concentration of Ropivacaine to Maintain Sensation of the Nerve Root in Percutaneous Endoscopic Transforaminal Lumbar Discectomy: Can Epidural Anaesthesia Achieve Pain-Tactile Separation Block to Avoid Nerve Injury?

Introduction: Nerve injury is a serious complication of percutaneous endoscopic transforaminal lumbar discectomy due to nerve root contact. The maximum tolerable concentration (MTC) of ropivacaine concentration for epidural anaesthesia, is defined as the concentration that minimises pain while preserving the sensation of the nerve roots. This distinct advantage allows the patient to provide feedback to the surgeon when the nerve roots are contacted. Methods: We used a biased-coin design to determine the MTC, which was estimated by the 10% effective concentration (EC10), ie, the concentration at which 10% of patients lost sensation in the nerve roots. The determinant for positive response was lack of sensory feedback upon contact with the nerve root, and the feedback from occurrence of sensations in the innervation area upon contact with the nerve root was defined as a negative response. Primary outcome was the response from contact nerve root. Secondary outcomes were the type and number of statements of negative response and each patient's pain score during surgery. Results: Fifty-four patients were included in this study. The EC10 was 0.434% (95% CI: 0.410%, 0.440%) using isotonic regression in comparison with 0.431% (95% CI: 0.399%, 0.444%) using probit regression. Three type statements of negative response were reported including "tactile sensation", radiculalgia, and numbness. Conclusion: The MTC of ropivacaine used for epidural anaesthesia was 0.434% to avoid nerve injury in percutaneous endoscopic transforaminal lumbar discectomy.

A portent of catastrophic carbon dioxide embolism in laparoscopic hepatectomy: A case report.

INTRODUCTION: Laparoscopic hepatectomy (LH) poses a high risk of carbon dioxide embolism due to extensive hepatic transection, long surgery duration, and dissection of the large hepatic veins or vena cava. PATIENT CONCERNS: A 65-year-old man was scheduled to undergo LH. Following intraperitoneal carbon dioxide (CO2) insufflation and hepatic portal occlusion, the patient developed severe hemodynamic collapse accompanied by a decrease in the pulse oxygen saturation (SpO2). DIAGNOSIS: Although a decrease in end-tidal carbon dioxide (ETCO2) was not observed, CO2 embolism was still suspected because of the symptoms. INTERVENTIONS AND OUTCOMES: The patient was successfully resuscitated after the immediate discontinuation of CO2 insufflation and inotrope administration. CO2 embolism must always be suspected during laparoscopic surgery whenever sudden hemodynamic collapse associated with decreased pulse oxygen saturation occurs, regardless of whether ETCO2 changes. Instant arterial blood gas analysis is imperative, and a significant difference between PaCO2 and ETCO2 is indicative of carbon dioxide embolism. CONCLUSION: Instant arterial blood gas analysis is imperative, and a significant difference between PaCO2 and ETCO2 is indicative of carbon dioxide embolism.

Comparing the efficacy and safety of high-voltage and standard-voltage pulsed radiofrequency for the treatment of postherpetic neuralgia: A pooled analysis from randomized controlled trials.

Postherpetic neuralgia (PHN) is one of the most common and serious complications of herpes zoster infection. Pulsed radiofrequency (PRF) therapy has emerged to be a neuromodulation technique for the treatment of PHN. Two therapeutic options are available for PRF, including high-voltage and standard-voltage PRF. Some studies suggested that the former one had better clinical efficacy than the latter one. For the first time, this pooled analysis compared the efficacy and safety of these two surgeries for the treatment of PHN. Five commonly used databases were applied to identify the eligible studies. This study was registered on the PROSPERO (ID: CRD42023460236), which provided more relevant information. Finally, four randomized controlled trials (RCTs) with 285 participants were included. The combined odds ratios (OR) showed that high-voltage PRF exhibited a significantly higher treatment efficiency than the standard PRF (OR = 1.4, 95%CI: 1.16 to 1.69, P < 0.001). Additionally, the visual analogue scale (VAS) in the high-voltage PRF group was significantly lower than that of the standard PRF group at one week (SMD = -0.776, 95%CI: -1.408 to -0.145, P = 0.016), one month (SMD = -0.544, 95%CI: -0.907 to -0.180, P = 0.003), and three months (SMD = -1.096, 95%CI: -1.504 to -0.687, P < 0.001) after treatment, particularly at the three months after surgery. However, the VAS was comparable between the two groups (SMD = -0.94, 95%CI: -1.985 to 0.104, P = 0.077). Patients who underwent high-voltage PRF did not have a significantly higher incidence of adverse events than those with standard PRF (OR = 1.56, 95%CI: 0.78 to 3.13, P = 0.208). In summary, the current study revealed that high-voltage PRF is superior to standard-voltage PRF in improving analgesic efficacy in patients with PHN. Additionally, it does not increase the incidence of treatment-related adverse effects. Further studies are still warranted to determine the optimal voltage and duration of PRF treatment for patients with PHN.

Major complications of caudal block: A prospective survey of 973 cases in adult anorectal surgery.

Background: We conducted a prospective study of surgical inpatients at a teaching hospital to assess the incidence and potential risk factors for major complications of caudal anesthesia in anorectal surgery. Methods: A total of 973 patients undergoing anorectal surgery under caudal block were included in this prospective, observer-blinded trial after providing consent. Demographic information, detailed perioperative information, anesthesia-related complications and postoperative follow-up information were recorded. Meanwhile, the incidence and risk factors for major caudal anesthesia-related complications were analyzed. Results: A total of 973 patients underwent caudal block. The effective rate was 95.38 % (928 cases). However, there were still 38 (3.91 %) cases with insufficient block and 7 (0.72 %) cases with no block. The major anesthesia-related complications were local anesthetic systemic toxicity (9, 0.92 %), cauda equine syndrome (1, 0.10 %), transient neurological symptoms (3, 0.31 %) and localized pain at the caudal insertion site (30, 3.08 %). The identified risk factor for local anesthetic systemic toxicity was multiple attempts locating the caudal space (OR = 5.30; 1.21-23.29). The identified risk factor for localized pain at the caudal insertion site was multiple attempts locating the caudal space (OR = 10.57; 4.89-22.86). Conclusion: The main complications of caudal block in adult patients are transient neurological symptoms, cauda equine syndrome, serious local anesthetic systemic toxicity and localized pain at the caudal insertion site. Overall, the incidence of complications is low and symptoms are mild. Caudal block is still a safe and reliable method for anesthesia in adult anorectal surgery.

UBE3A and MCM6 synergistically regulate the proliferation and migration of lung adenocarcinoma cells.

Lung cancer is a leading cause of mortality worldwide and shows substantial clinical and biomolecular heterogeneity. Currently, specific therapeutic strategies are lacking, so effective drug targets are urgently needed. E6AP/UBE3A is a multifaceted ubiquitin ligase that controls various signaling pathways implicated in neurological diseases and various cancers; however, its role in lung cancer is incompletely understood. Here, MCM6 was identified as an interacting partner of E6AP using the yeast two-hybrid assay. MCM2 and MCM4 were then shown to interact with E6AP. E6AP knockout enhanced the ubiquitination of MCM2/4/6, suggesting that E6AP was not the E3 ubiquitin ligase for these three MCM proteins. Ablation of E6AP inhibited proliferation and migration, but had no significant effect on apoptosis in A549 and H1975 cells, and proliferation and migration inhibition was also observed in MCM6 knockdown cells. Furthermore, ablation of MCM6 and E6AP synergistically suppressed the proliferation and migration of A549 and H1975 cells. To verify the above findings in vivo, we established tumor models in nude mice and identified that the tumorigenicity of human lung adenocarcinoma (LUAD) cells was synergistically regulated by MCM6 and E6AP. Moreover, the expression levels of MCM6 and E6AP were higher in LUAD tissues than in adjacent tissues. Furthermore, the expression levels of MCM6 and E6AP were positively correlated in human LUAD samples. Thus, our study suggests that the interaction of E6AP and MCM proteins plays an important role in the progression of LUAD, which might offer potential therapeutic targets for cancer treatment.

Neuroinflammatory Biomarkers in the Brain, Cerebrospinal Fluid, and Blood After Ischemic Stroke.

The most frequent type of stroke, known as ischemic stroke (IS), is a significant global public health issue. The pathological process of IS and post-IS episodes has not yet been fully explored, but neuroinflammation has been identified as one of the key processes. Biomarkers are objective indicators used to assess normal or pathological processes, evaluate responses to treatment, and predict outcomes, and some biomarkers can also be used as therapeutic targets. After IS, various molecules are produced by different cell types, such as microglia, astrocytes, infiltrating leukocytes, endothelial cells, and damaged neurons, that participate in the neuroinflammatory response within the ischemic brain region. These molecules may either promote or inhibit neuroinflammation and may be released into extracellular spaces, including cerebrospinal fluid (CSF) and blood, due to reasons such as BBB damage. These neuroinflammatory molecules should be valued as biomarkers to monitor whether their expression levels in the blood, CSF, and brain correlate with the diagnosis and prognosis of IS patients or whether they have potential as therapeutic targets. In addition, although some molecules do not directly participate in the process of neuroinflammation, they have been reported to have potential diagnostic or therapeutic value against post-IS neuroinflammation, and these molecules will also be listed. In this review, we summarize the neuroinflammatory biomarkers in the brain, CSF, and blood after an IS episode and the potential value of these biomarkers for the diagnosis, treatment, and prognosis of IS patients.

Development and validation of a nomogram for postoperative sleep disturbance in adults: a prospective survey of 640 patients undergoing spinal surgery.

BACKGROUND: Postoperative sleep disturbance (PSD) is a prevalent clinical complication that may arise due to various factors. The purpose of this investigation is to identify the risk factors for PSD in spinal surgery and establish a risk prediction nomogram. METHODS: The clinical records of individuals who underwent spinal surgery from January 2020 to January 2021 were gathered prospectively. The least absolute shrinkage and selection operator (LASSO) regression, along with multivariate logistic regression analysis, was employed to establish independent risk factors. A nomogram prediction model was devised based on these factors. The nomogram's effectiveness was evaluated and verified via the receiver operating characteristic (ROC) curve, calibration plot, and decision curve analysis (DCA). RESULTS: A total of 640 patients who underwent spinal surgery were analyzed in this investigation, among which 393 patients experienced PSD with an incidence rate of 61.4%. After conducting LASSO regression and logistic regression analyses using R software on the variables in training set, 8 independent risk factors associated to PSD were identified, including female, preoperative sleep disorder, high preoperative anxiety score, high intraoperative bleeding volume, high postoperative pain score, dissatisfaction with ward sleep environment, non-use of dexmedetomidine and non-use of erector spinae plane block (ESPB). The nomogram and online dynamic nomogram were constructed after incorporating these variables. In the training and validation sets, the area under the curve (AUC) in the receiver operating characteristic (ROC) curves were 0.806 (0.768-0.844) and 0.755 (0.667-0.844), respectively. The calibration plots indicated that the mean absolute error (MAE) values in both sets were respectively 1.2% and 1.7%. The decision curve analysis demonstrated the model had a substantial net benefit within the range of threshold probabilities between 20% and 90%. CONCLUSIONS: The nomogram model proposed in this study included eight frequently observed clinical factors and exhibited favorable accuracy and calibration. TRIAL REGISTRATION: The study was retrospectively registered with the Chinese Clinical Trial Registry (ChiCTR2200061257, 18/06/2022).

Progresses, Challenges, and Prospects of CRISPR/Cas9 Gene-Editing in Glioma Studies.

Glioma refers to a tumor that is derived from brain glial stem cells or progenitor cells and is the most common primary intracranial tumor. Due to its complex cellular components, as well as the aggressiveness and specificity of the pathogenic site of glioma, most patients with malignant glioma have poor prognoses following surgeries, radiotherapies, and chemotherapies. In recent years, an increasing amount of research has focused on the use of CRISPR/Cas9 gene-editing technology in the treatment of glioma. As an emerging gene-editing technology, CRISPR/Cas9 utilizes the expression of certain functional proteins to repair tissues or treat gene-deficient diseases and could be applied to immunotherapies through the expression of antigens, antibodies, or receptors. In addition, some research also utilized CRISPR/Cas9 to establish tumor models so as to study tumor pathogenesis and screen tumor prognostic targets. This paper mainly discusses the roles of CRISPR/Cas9 in the treatment of glioma patients, the exploration of the pathogenesis of neuroglioma, and the screening targets for clinical prognosis. This paper also raises the future research prospects of CRISPR/Cas9 in glioma, as well as the opportunities and challenges that it will face in clinical treatment in the future.

Research Progress on Serratus Anterior Plane Block in Breast Surgery: A Narrative Review.

Breast surgery, especially radical mastectomy, is often accompanied by moderate to severe acute pain, which significantly reduces postoperative quality of life. Effective pain management can accelerate patient recovery. Serratus anterior plane block (SAPB) is a new type of fascial plane block technique, which can better target the nerve network innervating the chest wall and breast and provide good analgesia in the anterolateral chest wall. Current clinical research evidence indicates that SAPB has significant benefits in breast surgery. Further research avenues for this technology include optimal local anesthetic dosing strategy, the type of SAPB which is more suitable for breast surgery, comparison of SAPB and pectoral nerve block II (PECS II) in breast surgery, and high-quality randomized controlled study with outcomes of chronic pain or cancer prognosis.

Single-cell RNA sequencing in the context of neuropathic pain: progress, challenges, and prospects.

Neuropathic pain, characterized by persistent or intermittent spontaneous pain as well as some unpleasant abnormal sensations, is one of the most prevalent health problems in the world. Ectopic nerve activity, central and peripheral nociceptive sensitization and many other potential mechanisms may participate in neuropathic pain. The complexity and ambiguity of neuropathic pain mechanisms result in difficulties in pain management, and existing treatment plans provide less-than-satisfactory relief. In recent years, single-cell RNA sequencing (scRNA-seq) has been increasingly applied and has become a powerful means for biological researchers to explore the complexity of neurobiology. This technique can be used to perform unbiased, high-throughput and high-resolution transcriptional analyses of neuropathic pain-associated cells, improving the understanding of neuropathic pain mechanisms and enabling individualized pain management. To date, scRNA-seq has been preliminarily used in neuropathic pain research for applications such as compiling a dorsal root ganglion atlas, identifying new cell types and discovering gene regulatory networks associated with neuropathic pain. Although scRNA-seq is a relatively new technique in the neuropathic pain field, there have been several studies based on animal models. However, because of the various differences between animals and humans, more attention should be given to translational medicine research. With the aid of scRNA-seq, researchers can further explore the mechanism of neuropathic pain to improve the clinical understanding of the diagnosis, treatment and management of neuropathic pain.

Research progress on the role of hormones in ischemic stroke.

Ischemic stroke is a major cause of death and disability around the world. However, ischemic stroke treatment is currently limited, with a narrow therapeutic window and unsatisfactory post-treatment outcomes. Therefore, it is critical to investigate the pathophysiological mechanisms following ischemic stroke brain injury. Changes in the immunometabolism and endocrine system after ischemic stroke are important in understanding the pathophysiological mechanisms of cerebral ischemic injury. Hormones are biologically active substances produced by endocrine glands or endocrine cells that play an important role in the organism's growth, development, metabolism, reproduction, and aging. Hormone research in ischemic stroke has made very promising progress. Hormone levels fluctuate during an ischemic stroke. Hormones regulate neuronal plasticity, promote neurotrophic factor formation, reduce cell death, apoptosis, inflammation, excitotoxicity, oxidative and nitrative stress, and brain edema in ischemic stroke. In recent years, many studies have been done on the role of thyroid hormone, growth hormone, testosterone, prolactin, oxytocin, glucocorticoid, parathyroid hormone, and dopamine in ischemic stroke, but comprehensive reviews are scarce. This review focuses on the role of hormones in the pathophysiology of ischemic stroke and discusses the mechanisms involved, intending to provide a reference value for ischemic stroke treatment and prevention.

The efficacy and safety of remifentanil patient-controlled versus epidural analgesia in labor: A meta-analysis and systematic review.

BACKGROUND: Remifentanil patient-controlled analgesia (rPCA) and epidural analgesia (EA) has been used for pain relief in labor. We aimed to evaluate the efficacy and safety of rPCA versus EA in labor, to provide evidence support for clinical analgesia and pain care. METHODS: We searched PubMed, EMBASE, ScienceDirect, Cochrane Library, China National Knowledge Infrastructure (CNKI), Wanfang and Weipu databases for RCTs comparing rPCA and EA in labor until February 15, 2022. Two researchers independently screened literature and extracted data. RevMan 5.3 software was used for data analysis. RESULTS: A total of 10 RCTs involving 3086 parturients were enrolled, 1549 parturients received rPCA and 1537 received EA. Meta-analysis indicated that the incidence of intrapartum maternal fever within 1 hour of labor analgesia (OR = 0.43, 95%CI: 0.30~0.62), after 1 hour of labor analgesia (OR = 0.42, 95%CI: 0.20~0.90) in the rPCA was significantly less than that of EA (all P<0.05). The incidence of respiratory depression (OR = 3.56, 95%CI: 2.45~5.16, P<0.001) in the rPCA was significantly higher than that of EA. There were no significant differences in the incidence of Apgar scores<7 at 5 minutes (OR = 1.18, 95%CI: 0.71~1.96, P = 0.53), the patients' satisfaction of pain relief during labor analgesia (SMD = 0.03, 95%CI: -0.40~0.46, P = 0.90) between rPCA and EA (all P>0.05). CONCLUSION: rPCA can be an optional alternative to EA with similar pain relief and less risk of intrapartum maternal fever. However, rPCA was associated with increased risk of respiratory depression. Future studies with rigorous design and larger sample size are needed to provide more reliable evidences for clinical rPCA and EA use.

Profile of Remimazolam in Anesthesiology: A Narrative Review of Clinical Research Progress.

Remimazolam is a novel short-acting γ-aminobutyric acid (GABA) receptor agonist with typical characteristics of benzodiazepine sedative drugs, nonorgan-dependent metabolism, long-term infusion without accumulation, and no injection pain. It is quite different from the other current sedative drugs and has broad prospects for application. It has been established that the metabolites of remimazolam are inactive, and the interactions with other drugs are weak with slight cardiopulmonary suppressive effects, showing good effectiveness and safety. During the 2-year period that it has been on the market, remimazolam has been used in multiple clinical scenarios, such as the induction and maintenance of general anesthesia and sedation in outpatient minor procedures or examinations. However, it's use has also prompted widespread concern around the world. Therefore, given its short- and rapid-acting, controllable characteristics remimazolam deserves in-depth study in order for it to be used in fast-track surgery, comfort diagnosis and treatment. Notably, such agents might be of great significance, especially in elderly individuals, patients with critical diseases or patients with liver and kidney insufficiency. The current study reviews recent clinical studies (2015-2022) on remimazolam and summarizes the characteristics of its applications. Specifically, the use of remimazolam in some specific populations are described. This study attempts to provide scientific support for the clinical application of this novel sedative drug in the field of anesthesia.

Recent Advances in Progresses and Prospects of IL-37 in Central Nervous System Diseases.

Interleukin-37 (IL-37) is an effective anti-inflammatory factor and acts through intracellular and extracellular pathways, inhibiting the effects of other inflammatory cytokines, such as IL-1ß, IL-6, and tumor necrosis factor-α (TNF-α), thereby exerting powerful anti-inflammatory effects. In numerous recent studies, the anti-inflammatory effects of IL-37 have been described in many autoimmune diseases, colitis, and tumors. However, the current research on IL-37 in the field of the central nervous system (CNS) is not only less, but mainly for clinical research and little discussion of the mechanism. In this review, the role of IL-37 and its associated inflammatory factors in common CNS diseases are summarized, and their therapeutic potential in CNS diseases identified.

Role of lipocalin-2 in surgery-induced cognitive decline in mice: a signal from neuron to microglia.

BACKGROUND: Perioperative neurocognitive disorders (PNDs) are common complications observed among surgical patients. Accumulating evidence suggests that neuroinflammation is one of the major contributors to the development of PNDs, but the underlying mechanisms remain unclear. METHODS: qPCR and ELISA analysis were used for detecting LCN2 and cytokine levels. cx3cr1CreER/-:: R26iDTR/- crossed mouse line was used for microglia depletion; intracranial injection of recombinant LCN2 (rLCN2) and adeno-associated viruses (AAV)-mediated shRNA silencing approaches were used for gain and loss of function, respectively. Combing with in vitro microglia cell culture, we have studied the role of LCN2 in surgery-induced cognitive decline in mice. RESULTS: We revealed that Lcn2 mRNA and protein levels were greatly increased in mouse hippocampal neurons after surgery. This surgery-induced elevation of LCN2 was independent of the presence of microglia. Gain of function by intracranial injection of rLCN2 protein into hippocampus disrupted fear memory in naive mice without surgery. Conversely, silencing LCN2 in hippocampus by AAV-shRNA protected mice from surgery-induced microglia morphological changes, neuroinflammation and cognitive decline. In vitro, application of rLCN2 protein induced the expression of several pro-inflammatory cytokines in both BV-2 and primary microglia culture. CONCLUSIONS: These data suggest LCN2 acts as a signal from neuron to induce proinflammatory microglia, which contributes to surgery-induced neuroinflammation and cognitive decline in mice.

Progress, Challenges, and Prospects of Research on the Effect of Gene Polymorphisms on Adverse Reactions to Opioids.

The abuse of opioids has become one of the most serious concerns in the world. Opioid use can cause serious adverse reactions, including respiratory depression, postoperative nausea and vomiting, itching, and even death. These adverse reactions are also important complications of clinical application of opioid drugs that may affect patient safety and recovery. Due to the fear of adverse reactions of opioids, clinicians often do not dare to use opioids in an adequate or appropriate amount, thus affecting the clinical medication strategy and the quality of treatment for patients. The prediction of adverse reactions to opioids is one of the most concerned problems in clinical practice. At present, the correlation between gene polymorphism and the efficacy of opiates has been widely studied and preliminarily confirmed, but the research on the effect of gene polymorphism on the adverse reactions of opiates is relatively limited. Existing studies have made encouraging progress in predicting the incidence and severity of adverse opioid reactions and clinical management by using genetic testing, but most of these studies are single-center, small-sample clinical studies or animal experiments, which have strong limitations. When the same receptor or enzyme is studied by different experimental methods, different or even opposite conclusions can be drawn. These phenomena indicate that the correlation between gene polymorphism and adverse opioid reaction still needs further research and demonstration. At present, it is still too early to use genetic testing to predict opioid adverse reactions in clinic. In this paper, the correlation between gene polymorphism and adverse opioid reactions and a small number of clinical applications were reviewed in terms of pharmacokinetics and pharmacodynamics, in order to provide some suggestions for future research and clinical drug decision making.

Comparison of Postoperative Pain in 70 Women with Breast Cancer Following General Anesthesia for Mastectomy with and without Serratus Anterior Plane Nerve Block.

BACKGROUND [color=black]This study was conducted at a single center and aimed to compare postoperative pain in 70 women with breast cancer following general anesthesia for mastectomy with and without serratus anterior plane (SAP) block.[/color] MATERIAL AND METHODS [color=black]A total of 70 breast cancer patients who met the criteria were randomly divided into the general anesthesia combined with SAP block group (group S) and the general anesthesia only group (group G). Perioperative anesthetic drug dosage, the visual analog scale (VAS) score at different time points, and the patient's satisfaction with analgesia 24 h after surgery, and incidence of postmastectomy pain syndrome (PMPS) were statistically analyzed in the 2 groups.[/color] RESULTS [color=black]Compared with group G, group S had lower intraoperative remifentanil dosages (P=0.003), a lower total amount of sufentanil via analgesia pump during the 24-h postoperative period (P<0.001), and lower VAS scores at 2 h, 4 h, and 8 h after surgery, and the differences were significant (P<0.05). Compared with group G, group S had a shorter first flatus time, got out of bed sooner, had a lower incidence of nausea and vomiting (P<0.05), and lower incidence of PMPS at 3 and 6 months after the operation (P<0.05).[/color] CONCLUSIONS [color=black]At a single center, preoperative SAP block can significantly reduce postoperative pain after modified radical mastectomy for breast cancer.[/color].

Determining the Minimum Effective Concentration of Ropivacaine in Epidural Anesthesia for Tolerable Pain in Transforaminal Percutaneous Endoscopic Lumbar Discectomy to Avoid Nerve Injury: A Double-Blind Study Using a Biased-Coin Design.

PURPOSE: Epidural anesthesia (EA) is the main anesthesia method for transforaminal percutaneous endoscopic lumbar discectomy (PELD). Reducing the concentration of ropivacaine can help preserve tactile sensation, allowing patients to provide timely feedback to the surgeons when a nerve root is contacted to avoid nerve injury. Therefore, a 90% effective concentration (EC90) that allows for mild pain [visual analog scale (VAS) score ≤3] while maximizing tactile sensation must be identified. METHODS: The concentration of ropivacaine for EA was varied for consecutive patients in this study using a two-stage biased-coin design (BCD) according to the response of the previous patient; the concentration used for the first patient was 0.2%. When the previous patient had a negative response (VAS score >3), the concentration used for the next one was increased by 0.015%. When the previous patient had a positive response (VAS score ≤3), the concentration used for the next one had an 89% probability of remaining the same and an 11% probability of being reduced by 0.015%. The EC90 of ropivacaine was estimated using isotonic regression, and the 95% confidence interval (CI) was estimated using the bootstrapping method in R. RESULTS: A total of 58 patients were included in the study. The calculated EC90 was 0.294% [95% CI (0.271%, 0.303%)]. Among 13 patients who reported unintended nerve root contact during the operation, none were found to have irreversible nerve injury after the operation. CONCLUSION: To preserve maximum tactile sensation, the EC90 of ropivacaine was 0.294% for patients with allowed mild pain. This concentration could allow for timely feedback when the nerve root is contacted, to avoid nerve injury.