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This randomized controlled trial compared ultrasound-guided L3-4 versus L5-S1 spinal anesthesia in total knee arthroplasty, evaluating highest sensory block level and multiple secondary outcomes including time to peak block, incisional sensory recovery, mean arterial pressure and heart rate changes, operative time, anesthesia satisfaction, vasopressor use, and postoperative complications.",{"@graph":69,"@context":122},[70,84,105],{"@type":71,"itemListElement":72},"BreadcrumbList",[73,77,79,82],{"item":74,"name":75,"@type":76,"position":8},"https://docshare.wps.com","Home","ListItem",{"item":78,"name":9,"@type":76,"position":14},"https://docshare.wps.com/document/",{"item":80,"name":35,"@type":76,"position":81},"https://docshare.wps.com/document/healthcare/",3,{"item":83,"name":65,"@type":76,"position":19},"https://docshare.wps.com/document/comparison-of-anesthetic-effects-of-spinal-anesthesia-at-l5-s1-and-l3-4-under-realtime-ultrasound-guidance-in-total-knee-arthroplasty-a-single-center-randomized-controlled-trial/442154/",{"url":83,"name":65,"@type":85,"image":86,"author":91,"headline":65,"publisher":94,"fileFormat":97,"inLanguage":63,"description":67,"dateModified":98,"datePublished":99,"encodingFormat":97,"isAccessibleForFree":100,"interactionStatistic":101},"DigitalDocument",{"url":87,"@type":88,"width":89,"height":90},"https://docshare.wps.com/thumbnails/comparison-of-anesthetic-effects-of-spinal-anesthesia-at-l5-s1-and-l3-4-under-realtime-ultrasound-guidance-in-total-knee-arthroplasty-a-single-center-randomized-controlled-trial/442154.png","ImageObject",300,407,{"name":92,"@type":93},"Mabel","Person",{"url":74,"name":95,"@type":96},"DocShare","Organization","application/pdf","2026-10-30","2026-09-29",true,{"@type":102,"interactionType":103,"userInteractionCount":52},"InteractionCounter",{"@type":104},"ViewAction",{"@type":106,"mainEntity":107},"FAQPage",[108,114,118],{"name":109,"@type":110,"acceptedAnswer":111},"What was the primary outcome of the trial?","Question",{"text":112,"@type":113},"The primary outcome was the comparison of the highest sensory block level between ultrasound-guided L3-4 and L5-S1 spinal anesthesia.","Answer",{"name":115,"@type":110,"acceptedAnswer":116},"How many patients were included, and how were they assigned?",{"text":117,"@type":113},"Forty-six total knee arthroplasty patients were randomized to group A (L5-S1) or group B (L3-4), with 23 patients in each group; 41 were used in the statistical analysis.",{"name":119,"@type":110,"acceptedAnswer":120},"What did the study find about hemodynamic stability?",{"text":121,"@type":113},"Compared with L3-4, the L5-S1 group showed a smaller decrease in mean arterial pressure and less frequent vasopressor use, indicating greater hemodynamic stability.","https://schema.org",{"og:url":83,"og:type":124,"og:title":65,"og:site_name":95,"og:description":67},"article",{"robots":126,"canonical":83},"index,follow",{"doc_id":128,"site_id":62},442154,1791089361,{"code":4,"msg":5,"data":131},{"doc_id":128,"user_id":132,"nickname":92,"user_avatar":133,"doc_module":4,"category_id":34,"category_name":35,"doc_title":65,"doc_description":67,"doc_content":134,"file_id":135,"file_url":136,"file_type":137,"file_size":138,"view_count":52,"is_deleted":4,"is_public":8,"is_downloadable":8,"audit_status":8,"page_count":52,"language":139,"language_code":63,"site_id":62,"html_lang":63,"table_of_contents":140,"faqs":141,"seo_title":142,"seo_description":67,"update_tm":143,"read_time":144,"preview_page_count":4},7971474920318,"https://ap-avatar.wpscdn.com/avatar/74000ee537e6b0ca360?x-image-process=image/resize,m_fixed,w_180,h_180&k=1788430171632181674","Liu et al. BMC Anesthesiology (2026) 26:17 [https://doi.org/10.1186/s12871-025-03483-3](https://doi.org/10.1186/s12871-025-03483-3)  \nBMC Anesthesiology  \nRESEARCH Open Access  \nComparison of anesthetic effects of spinal anesthesia at L5-S1 and L3-4 under realtime ultrasound guidance in total knee arthroplasty: a single center randomized controlled trial  \nYuekun Liu 1, Haiyan Li 1, Jinqin Bi 1, Chengrun Lu 1, Wenchao Li 1, Xiangguo Chai 1, Pei Ye 1, Qian Zhang 1, Guangping Qian2, Zhihai Li3 and Hongjiang Zhang3*  \nAbstract  \nBackground Spinal anesthesia at L5-S1 is rarely used and many characteristics of L5-S1 spinal anesthesia are not well-documented in the literature. Objective：The primary outcome measure was to compare the highest sensory block level between ultrasound guided L3-4 and L5-S1 spinal anesthesia. Secondary outcomes were the time required to reach the highest sensory block level, the incisional sensory block recovery time, the mean arterial pressure (MAP), heart rate and their changes at each time point during the operation, the operative time, the satisfaction rate of anesthesia, the use of vasopressors, and the incidence of post-operative complications.  \nMethods 46 patients who underwent total knee arthroplasty from December 2023 to December 2024 were randomly divided into L5-S1 (group A) and L3-4 (group B) with 23 cases each. In statistical analysis, 41 cases were used. 2 patients were excluded due to missing data in group A. In group B, 1 patient was converted to general anesthesia due to inability to perform spinal puncture because of difficult anatomy, 1 patient received excessive local anesthetic injection at the surgical site, and 1 patient had missing data. All patients were treated with paramedian approach spinal anesthesia under in-plane real-time ultrasound guidance. After successful puncture, 15mg of 0 . 75% bupivacaine (0 . 75% bupivacaine 2ml + cerebrospinal fluid 1ml) was injected. A third party recorded all primary and secondary outcomes.  \nResults In the L5-S1 group, the highest sensory block level was lower and the total number of spinal segments blocked were fewer, the time to reach highest sensory block level was longer, and the recovery time of incisional sensory block was longer (P \u003C 0. 001) . The decrease in MAP was smaller, and the use of vasopressors was less frequent (P \u003C 0. 05), with greater hemodynamic stability in the L5-S1 group. The satisfaction rate of anesthesia in both groups was 100% .  \n*Correspondence: Hongjiang Zhang [375056229@qq.com](375056229@qq.com)  \nFull list of author information is available at the end of the article  \n© The Author(s) 2025. Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit [http://creati](http://creati)[vecommons.org/l](vecommons.org/l)icenses/by-nc-nd/4.0/.  \nLiu et al. BMC Anesthesiology (2026) 26:17 Page 2 of 10  \nConclusion Under real-time ultrasound guidance, L5-S1spinal anesthesia has many benefits compared to L3-L4 spinal anesthesia.  \nTrial registration This trial was registered on July 21, 2025 at the Chinese Clinical Trial center (No","cbCaivJhBZzJW8mC","https://ap.wps.com/l/cbCaivJhBZzJW8mC","pdf",2184037,"English","# Abstract\n## Background and objective\n## Methods\n## Results\n## Conclusion\n# Keywords\n# Background and rationale","[{\"question\":\"What was the primary outcome of the trial?\",\"answer\":\"The primary outcome was the comparison of the highest sensory block level between ultrasound-guided L3-4 and L5-S1 spinal anesthesia.\"},{\"question\":\"How many patients were included, and how were they assigned?\",\"answer\":\"Forty-six total knee arthroplasty patients were randomized to group A (L5-S1) or group B (L3-4), with 23 patients in each group; 41 were used in the statistical analysis.\"},{\"question\":\"What did the study find about hemodynamic stability?\",\"answer\":\"Compared with L3-4, the L5-S1 group showed a smaller decrease in mean arterial pressure and less frequent vasopressor use, indicating greater hemodynamic stability.\"}]","Comparison of anesthetic effects of spinal anesthesia at L5-S1 and L3-4 under realtime ultrasound guidance in total knee arthroplasty - a single center randomized controlled trial | PDF",1790699227,25]