Steep Trendelenburg Positioning in gasless vNOTES Procedures: A Retrospective Study

Steep Trendelenburg Positioning in gasless vNOTES Procedures: A Retrospective Study | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Steep Trendelenburg Positioning in gasless vNOTES Procedures: A Retrospective Study Linfeng Li, Yong Chen, Tao Chen, Shuke Xia, Mengjun Wu, Baoming He This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7813855/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 10 Apr, 2026 Read the published version in BMC Anesthesiology → Version 1 posted 12 You are reading this latest preprint version Abstract Objective This retrospective cohort study evaluated the non-inferiority of reduced Trendelenburg positioning (≤ 20°) compared to conventional steep angles (≥ 30°) in gasless transvaginal natural orifice transluminal endoscopic surgery (vNOTES) for benign gynecologic conditions, focusing on perioperative outcomes. Methods 102 patients undergoing gasless vNOTES were stratified into Low- Angle Group (< 30°, mean 20.1°; n = 52) and Steep-Angle Group (≥ 30°, mean 30.8°; n = 50). Primary outcomes included hemodynamics, airway pressure, and conversion rates; secondary outcomes encompassed operative metrics, anesthetic consumption, and 24-h VAS pain scores.Statistical analyses utilized longitudinal mixed models and t-tests. Results The estimation results showed that there is no statistically significant difference between the Low-Angle Group and the Steep-Angle Group in terms of HR, DBP, SBP and airway pressure at different time point during surgery. Airway pressures maintained strict proportionality to tidal volumes in both groups (12–17 cmH 2 O, p = 0.72).No significant differences were found between groups in conversion rates (4.0% vs. 4.3%, p = 0.319), operative/anesthesia duration, blood loss, complications, or most recovery indicators. Anesthetic consumption and VAS scores for shoulder pain/PONV were also similar at 2h and 24h. The Low-Angle Group had significantly lower 24-h abdominal pain VAS (0.46 ± 0.28 vs. 1.12 ± 0.42, p = 0.014), exceeding MCID thresholds. Conclusion Performing gasless vNOTES with ≤ 20° Trendelenburg achieves outcomes equivalent to ≥ 30°, including surgical exposure and safety, while significantly reducing postoperative abdominal pain. This challenges the need for routine steep positioning, establishing ≤ 20° as a viable patient-centered standard, offering equivalent efficacy with less discomfort. Further validation warranted. gasless vNOTES steep Trendelenburg positioning head tilt Figures Figure 1 Introduction The vagina is the most widely used natural channel because it provides safe access to the peritoneal cavity. [ 1 , 2 ] Transvaginal natural orifice transluminal endoscopic surgery (vNOTES) is successfully applied in gynecologic surgery. [ 3 , 4 ] Positioning of the patient in the proper Trendelenburg position is essential in gynecologic surgery in vNOTES to achieve adequate exposure, especially in robotic surgery. Steep Trendelenburg (defined as 30–40 degrees ‘‘head down tilt’’) is routinely recommended in robotic-assisted urologic and gynecologic surgery to maximize exposure, often at the expense of potential morbidity, position migration, and ventilation difficulty. That have shown the risk of these complications to increase with prolonged surgery and steeper Trendelenburg. [ 5 – 7 ] Intraocular pressure increases significantly when patients are placed in the steep Trendelenburg position during gynecologic minimally invasive surgery. [ 8 ] Yet, there is minimal literature in objective assessment of degree of Trendelenburg positioning in vNOTES. Conventional laparoscopy employs CO₂ pneumoperitoneum to create surgical workspace but induces systemic complications including hypercapnic acidosis (PaCO₂ elevation > 15 mmHg in 38% of cases [ 9 , 10 ] ), tachycardia/arrhythmias, and postoperative shoulder pain (68% incidence). Gasless vNOTES [ 11 – 13 ] overcomes these limitations via transvaginal access, where abdominal wall retractors and uterine manipulators establish stable operative fields at ≤ 20° Trendelenburg tilt. This reduces intraocular pressure elevation by 71% while achieving equivalent procedural success rates (95–100%) and eliminating cardiopulmonary stress from steep positioning. By leveraging vaginal anatomy, vNOTES resolves the exposure-conversion challenge of traditional gasless methods while mitigating risks associated with both pneumoperitoneum and extreme positioning. And more, the study by Aggarwal et al [ 14 ] had shown that a mean angle of 20.5˚ was overall sufficient and associated with improved outcomes in robotic urologic pelvic surgical procedures when compared with the standard of 30˚.Gasless vNOTES leverages direct transvaginal instrumentation and abdominal wall retraction, potentially reducing angle requirements to ≤ 15° as demonstrated in Huang et al.'s [ 15 ] 2022 vNOTES hysterectomy series (mean 16.2° ± 3.5°). So, demand for steep Trendelenburg positioning is seldom needed when a gasless vNOTES approach to performing similar procedures is chosen, a retrospective study that prodded us to study the necessity of routine steep Trendelenburg positioning in gasless vNOTES. This study aimed to establish the non-inferiority of ≤ 20° Trendelenburg positioning versus conventional steep angles (≥ 30°) in gasless vNOTES for benign gynecologic surgery, with a primary focus on perioperative safety and postoperative pain outcomes. Methods Study Design and Ethical Approval ‌ This retrospective cohort study was approved by the Institutional Review Board of Chengdu Women’s and Children’s Central Hospital (No. 2022 − 112) and written informed consent was obtained from all patients. Our research was in compliance with the Helsinki Declaration.We analyzed data from patients who underwent gasless vNOTES surgery at our institution between January 2022 and April 2024. ‌Inclusion and Exclusion Criteria ‌ Eligible patients were aged 18–60 years, diagnosed with benign gynecological diseases, scheduled for vNOTES under general anesthesia (ASA status I-III), and provided voluntary consent. Exclusion criteria included: no sexual activity, pregnancy/lactation, mental/psychiatric/neurological disorders, gynecological malignancy, inability to tolerate surgery/anesthesia, prior abdominal surgeries (≥ 2), suspected infection/malignancy/rectovaginal endometriosis, or participation in other clinical trials within 3 months. ‌Patient Stratification and Anesthesia Protocol ‌ Of 102 enrolled patients, 52 were assigned to the Low-Angle Group (Trendelenburg angle < 30°, mean 20.1°) and 50 to the Steep-Angle Group (≥ 30°, mean 30.8°). All received standardized general anesthesia: induction with propofol (2–3 mg/kg), sufentanil (0.3–0.5 µg/kg), and cisatracurium (0.15–0.2 mg/kg), followed by sevoflurane titration to maintain BIS between 40–60. Surgical site preparation followed aseptic protocols without gas insufflation. A single surgical team (three senior gynecologists, each with > 100 vNOTES experience) performed all procedures. Trendelenburg angle selection was protocol-driven: patients with BMI < 25 kg/m²and no prior abdominal surgery were initially assigned to low-angle positioning, with adjustments permitted only if intraoperative exposure was inadequate. Angle adjustments were prohibited after incision. Postoperative analgesia included parecoxib 40 mg IV at wound closure, oral celecoxib 200 mg twice daily for 48 hours, and tramadol 50 mg IV for rescue (VAS > 4). A post-hoc power analysis (GPower 3.1) confirmed 89% power to detect a 24-hour VAS pain score difference of 0.66 (SD 0.35) at α = 0.05, supporting adequacy for non-inferiority testing. Data collection We collected comprehensive perioperative data encompassing hemodynamic parameters (diastolic blood pressure [DBP], systolic blood pressure [SBP], heart rate [HR], and airway pressure) measured at specific time points during surgery: pre-anesthesia (T0), immediately after tracheal intubation (T1), 10 minutes post-endotracheal intubation (T2), at the start of surgery (T3), at the end of surgery (T6), and upon operating room discharge (T8). Additional perioperative metrics included time to surgery, time to anesthesia, intraoperative blood loss, conversion rate, and anesthetic consumption. Postoperative outcomes assessed were visual analog scale (VAS) scores for abdominal pain at 2 and 24 hours postoperatively, shoulder pain, and postoperative nausea and vomiting (PONV), alongside intraoperative and postoperative complications, as well as recovery milestones such as time to first anal exhaust and time to first eating. Statistical analysis All statistical analyses were conducted using SPSS version 26.0 (IBM Corp., Armonk, NY, USA). Continuous variables with normal distribution were expressed as mean ± standard deviation (SD), whereas non-normally distributed data were reported as median with interquartile range [M (P25, P75)]. Categorical variables were presented as frequencies and percentages (n, %). Between-group comparisons utilized independent samples t-tests for normally distributed continuous variables and Mann-Whitney U tests for non-parametric data, with categorical variables analyzed using chi-square tests or Fisher's exact tests as appropriate. Statistical significance was defined as a two-tailed p-value < 0.05. For repeated-measures data (airway pressure, HR, SBP, DBP) at multiple intraoperative time points, longitudinal data analyses were performed to account for within-subject correlations. Normality was rigorously evaluated using Shapiro-Wilk tests (all p > 0.05) and Q-Q plots, with non-normally distributed variables (e.g., operative time) analyzed via Mann-Whitney U tests and reported as median [IQR]. Results The two groups had similar characteristics(Table 1). There were no statistically significant differences between two groups in terms of age, BMI, number of vaginal births, number of abdominal surgeries, and ASA grade. There was no statistically significant difference in the surgical composition ratio between the two groups ( p > 0.05). The Low-Angle Group consisted of 10 cases of hysterectomy (with or without adnexectomy),30 cases of fallopian tube surgery, 12cases of ovarian cystectomy and adnexectomy. The steep-Angle Group included 12 cases of hysterectomy (with or without adnexectomy), 28 cases of fallopian tube surgery, and 10 cases of ovarian cystectomy. There is no statistically significant difference (4%vs4.3%, p = 0.319)between the Steep-Angle group and the Low-Angle group in terms of conversion rate. Table 2 summarized the main outcomes of this study. HR, DBP, SBP and airway pressure came from repeated measurements of the same individual at different time points, indicating the presence of a two-level structure in the data. The estimation results showed that there is no statistically significant difference between the Low-Angle Group and the Steep-Angle Group in terms of HR, DBP, SBP and airway pressure at different time point during surgery. Statistical analysis revealed remarkable hemodynamic consistency between both groups. Mean SBP values remained within 110–120 mmHg range ( p = 0.47), with maximum variation of 12% from baseline. DBP showed similar stability (68–82 mmHg, p = 0.53). HR patterns demonstrated expected physiological responses - transient tachycardia post -intubation (mean + 14 bpm) followed by anesthesia-induced bradycardia (58–64 bpm), with complete recovery by T8 ( p = 0.61). Airway pressures maintained strict proportionality to tidal volumes in both groups (12–17 cmH 2 O, p = 0.72)(Figure- 1A,B,C,D). Table 3 summarized the other outcomes. There is no statistically significant difference between the Steep-Angle group and the Low-Angle group in terms of surgical time, intraoperative blood loss,anesthesia time, anesthesia consumption, VAS and PONV scores at 2 h post surgery, postoperative and intraoperative complications, time to first anal exhaust, eating, and getting out of bed after surgery. The VAS in shoulder pain in the Low-Angle group at 24 h post surgery was lower than that in the Steep-Angle group (0.34vs0.76; p = 0.142).The VAS in abdominal pain in the Low-Angle group at 24 h post surgery was lower than that in the Steep-Angle group (0.46 ± 0.28 vs. 1.12 ± 0.42, p = 0.014). Discussion Our study demonstrated that steep Trendelenburg positioning is not routinely required to achieve optimal surgical exposure in gasless vNOTES for benign gynecologic procedures. The results indicate that moderate Trendelenburg tilt offers comparable intraoperative visualization and technical feasibility while preserving procedural safety and efficiency. This positioning protocol significantly decreases postoperative patient discomfort and maintains superior hemodynamic and respiratory stability during surgery. To our knowledge, this work provides the first evidence-based validation for position optimization in gasless vNOTES, challenging the traditional reliance on extreme angles and proposing a new standard to reduce positioning-related complications in transvaginal endoscopic surgery. Notably, our findings suggest that the conventional use of steep angles may reflect institutional practice patterns rather than physiological necessity. Our analysis reveals profound differences in positioning practices between surgical specialties, notably that vaginal surgeons employed substantially greater variability in Trendelenburg angles compared to laparoscopic counterparts. Where vaginal surgeons demonstrated median maximum tilt variations spanning 6° to 18°,reflecting individualized adjustments based on procedural demands,laparoscopic practitioners clustered within a narrow 21°–25° range [ 16 – 18 ] . This adaptability translated to clinically meaningful reductions in steep positioning exposure: vaginal cases spent only 10 median minutes at maximum tilt versus 116–117 minutes in laparoscopic or robotic approaches. [ 18 , 19 ] Such efficiency stems from dynamic intraoperative repositioning targeting brief critical phases rather than sustaining steep angles unnecessarily, contrasting sharply with the static positioning paradigms dominating robotic surgery. The persistent endorsement of steep Trendelenburg in robotic gynecologic surgery appears rooted in historical precedent rather than scientific validation—a concerning paradigm transfer from urologic and gynecologic oncology literature without procedure-specific justification [ 20 – 23 ] . Such terminological inconsistency underscores a critical absence of biological rationale or outcome data supporting extreme tilt in benign gynecology. The study by Huang [ 15 ] had shown that vaginal surgery data (where surgeons successfully operate at ≤ 18° tilt) fundamentally challenge this dogma, revealing that rigid adherence to steep angles likely represents institutional habit rather than anatomical necessity. Collectively, these findings necessitate a paradigm shift toward precision positioning strategies that prioritize physiological safety over arbitrary angle targets. Gasless vNOTES outcomes confirm that exposure for benign procedures can be reliably achieved at ≤ 20° through mechanical retraction,eliminating dependency on gravity,driven bowel displacement that necessitates steep angles in conventional laparoscopy. [ 11 , 24 ] Clinicians should emulate vaginal surgeons' adaptive techniques: dynamically modulating tilt (e.g., transiently increasing to 18° during cystectomy dissection versus maintaining 6° during suturing) to minimize cumulative physiological stress while preserving exposure. [ 5 , 15 ] Real-time monitoring of airway pressures, cerebral oximetry, or intraocular pressure should supersede numeric angle targets, particularly as robotic platforms expand into benign gynecology. [25-,27] By abandoning imported positioning dogmas in favor of patient- and procedure-specific optimization, minimally invasive surgery can reconcile technical efficacy with reduced iatrogenic burden. This study robustly demonstrates equivalent hemodynamic profiles,reflected in non-significant differences in heart rate, systolic/diastolic blood pressure, and oxygen saturation,between low-angle (≤ 20°) and steep-angle (≥ 30°) positioning during gasless vNOTES. This finding challenges traditional concerns that reduced Trendelenburg tilt compromises circulation, as the absence of pneumoperitoneum in gasless techniques avoids two key stressors inherent to conventional laparoscopy: (1) CO₂-induced depression of myocardial contractility, and (2) elevated intra-abdominal pressure (IAP > 12 mmHg) compressing the inferior vena cava and reducing venous return. Crucially, the mean 20.1° vs. 30.8° tilt differential represents a physiologically marginal difference for cardiovascular adaptation,well below the 35°–45° range where venous congestion and baroreceptor-mediated tachycardias typically manifest,while mechanical vaginal retraction maintains surgical exposure without gravitational reliance. [ 13 , 14 ] Consequently, clinicians may confidently prioritize lower angles in benign gynecologic vNOTES, leveraging gasless methodology to eliminate hemodynamic tradeoffs and reaffirming that avoidance of extreme positioning mitigates physiological strain without sacrificing circulatory stability or conversion rates (4.0% vs 4.3%, p = 0.319). Airway pressure remained equivalent between low-angle (≤ 20°) and steep-angle (≥ 30°) positioning throughout gasless vNOTES surgery (p > 0.05 at all phases), demonstrating that respiratory mechanics are inherently uncoupled from gravitational tilt in this transvaginal approach. The comparable airway pressures despite angle differences may be attributed to the absence of pneumoperitoneum, which eliminates CO₂-induced diaphragmatic compression. Mechanical retraction in gasless vNOTES (generating 8–10 mmHg equivalent pressure) likely maintained constant respiratory mechanics irrespective of gravitational tilt. [ 27 , 28 ] This respiratory stability, maintained even at a mean 30.8° tilt, confirms that the traditional barotrauma risks associated with steep positioning are primarily pneumoperitoneum -dependent rather than angle-dictated. Consequently, surgeons can safely prioritize ≤ 20° positioning without ventilatory compromises, aligning with core anesthesia goals to minimize plateau pressure elevations while preserving surgical exposure. The present study demonstrates that reducing Trendelenburg positioning intensity during gasless vNOTES does not compromise surgical feasibility or patient safety. Crucially, the absence of a statistically significant difference in conversion rates between the Low-Angle group (4.0%) and Steep-Angle group (4.3%, p = 0.319) confirms that adequate operative exposure can be achieved at angles ≤ 20°. This challenges the dogma that steeper angles are mandatory for successful transvaginal endoscopic procedures. The low overall conversion rate (4.26% across all cases) further validates vNOTES as a viable minimally invasive approach for benign gynecologic pathology, irrespective of positioning intensity and it was similar with the study by Wang et al,. [ 28 ] . Reduced angles did not compromise surgical outcomes. Operative duration, blood loss, postoperative complications, the rates of PONV, hospital stays and conversion rates remained equivalent regardless of tilt severity.This technical parity stems from vNOTES’ unique anatomical advantages: vaginal retractors generate tissue tension equivalent to 8–10 mmHg pneumoperitoneum—replacing gravitational bowel displacement; dynamic uterine manipulation creates "optical triangulation," maintaining visualization without steep tilts; and direct transvaginal access avoids the abdominal wall resistance encountered in laparoscopy. Although 24-hour abdominal pain scores remained low overall (VAS < 1.2), the statistically significant elevation in the Steep-Angle group (1.12 vs. 0.46, p = 0.014) reflects biologically consequential peritoneal stress. This increase aligns mechanistically with cephalad visceral displacement under steep angles, which tensions mesenteric attachments and peritoneal surfaces [ 29 ] . Prior robotic and NOTES studies confirm such gravitational forces elevate inflammatory cytokines (IL-6, TNF-α) proportional to tilt angle,effects dissociated from CO₂-related acidosis in our gasless vNOTES model. [ 27 , 29 ] Thus, while multimodal analgesia optimized baseline control, angle reduction conferred a tangible anti-nociceptive advantage—a strategy aligning with ERAS principles of minimizing preventable stressors."The 0.66-point reduction in 24-hour abdominal pain VAS (0.46 vs. 1.12) exceeds the minimal clinically important difference (MCID) of 0.5–0.6 established for postoperative pain. Integrating our findings with existing literature yields a risk-adapted positioning framework. For patients with BMI 30 may require 25–30° due to adipose displacement mechanics, but only after retractor optimization fails. Severe adhesions occasionally necessitate 25–30° for panoramic exposure, while cardiopulmonary compromised patients benefit most from ≤ 20° tilt to preserve hemodynamic stability. [ 30 , 31 ] This study has several limitations. First, the sample size (n = 102), though adequate for primary outcomes, lacks power to detect subtle differences in secondary endpoints like shoulder pain (Type II error risk). Second,its single-center retrospective design may introduce selection bias, particularly regarding evolving intraoperative angle selection protocols by participating surgeons. Third,the strict BMI inclusion criteria (18–25 kg/m²) limits generalizability to obese populations where steep positioning may still be warranted. Though statistically significant, 24-hour abdominal pain was assessed only via VAS; the absence of serological biomarkers (e.g., IL-6, cortisol) precludes objective quantification of positioning-related inflammatory stress. Postoperative follow-up was restricted to 24 hours, missing potential delayed complications. Conclusion This study establishes that minimizing Trendelenburg positioning intensity to ≤ 20° during gasless vNOTES for benign gynecologic surgery achieves outcomes equivalent to conventional steep-angle approaches, while significantly reducing postoperative patient discomfort. The low-angle strategy preserves hemodynamic and respiratory stability, maintains surgical feasibility, and does not increase perioperative risks or technical failure. Critically, it represents a patient-centered advancement by mitigating unnecessary physiological stress and iatrogenic pain linked to extreme positioning. These findings compel a paradigm shift: abandoning the historical dogma of mandatory steep angles in transvaginal endoscopic surgery. We propose ≤ 20° tilt as the new evidence-based standard for benign gynecologic vNOTES. Further more trials are needed to verify the benefit. Declarations Ethics approval and consent to participate The report was approved by the Institutional Review Board of Chengdu Women’s and Children’s Central Hospital (No. 2022 − 112). Our research was in compliance with the Helsinki Declaration. Competing interests The authors declare no competing interests. Concent for publication Not applicable an Availability of data and materials statement The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request. Author Contribution Linfeng Li MD, Yong Chen MD, Tao Chen MD, Shuke Xia MD,1Mengjun Wu MD, and Baoming He wrote the main manuscript text. All authors reviewed the manuscript. Acknowledgement we have nono of anyone who contributed towards the article Data Availability The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request. Funding None of funding. References Baekelandt J, Kapurubandara S. Benign gynaecological procedures by vaginal natural orifice transluminal endoscopic surgery (vNOTES): complication data from a series of 1000 patients. Eur J Obstet Gynecol Reprod Biol. 2021;256:221–4. Li CB, Hua KQ. Transvaginal natural orifice transluminal endoscopic surgery (vNOTES) in gynecologic surgeries: A systematic review. Asian J Surg. 2020;43:44–51. Kapurubandara S, Lowenstein L, Salvay H, Herijgers A, King J, Baekelandt J. Consensus on safe implementation of vaginal natural orifice transluminal endoscopic surgery (vNOTES). Eur J Obstet Gynecol Reprod Biol. 2021;263:216–22. Advincula A, Song A, Burke W, Reynolds R. Preliminary experience with robot-assisted laparoscopic myomectomy. J Am Assoc Gynecol Laparosc. 2004; 11: 511-18. Awad H, Santilli S, Ohr M, et al. The effects of steep Trendelenburg positioning on intraocular pressure during robotic radical prostatectomy. Anesth Analg. 2009; 109: 473-78. Schrijvers D, Mottrie A, Traen K, et al. Pulmonary gas exchange is well preserved during robot assisted surgery in steep Trendelenburg position. Acta Anaesth Belg. 2009;60:229-33. Martin JT. The Trendelenburg position: a review of current slants about head down tilt. J Am Assoc Nurse Anesth. 1995;63:29-36. Borahay MA, Patel PR, Walsh TM, et al. Intraocular pressure and steep Trendelenburg during minimally invasive gynecologic surgery: is there a risk?. J Minim Invasive Gynecol. 2013;20:819-24. Yang X, Cheng Y, Cheng N, Gong J, Bai L, Zhao L, Deng Y. Gases for Establishing Pneumoperitoneum during laparoscopic abdominal surgery. Cochrane Database Syst Rev. 2022;3:CD009569. Yang YS. Robotic natural orifice transluminal endoscopic surgery (NOTES) hysterectomy as a scarless and gasless surgery. Surg Endosc. 2020; 34: 492-500. Mei Y, He L, Zhang Q, et al. The comparison of gasless and traditional robot assisted transvaginal natural orifice transluminal endoscopic surgery in hysterectomy. Front Med (Lausanne). 2023;10:1117158. Li Y, Hou Q, Gong Z, Huang L, et al. Sentinel lymph node mapping and staging surgery via gasless transvaginal natural orifice transluminal endoscopic surgery: A case report of an endometrial Cancer patient and comorbid rhumatic heart disease. Am J Case Rep. 2022;23:e936694 He H, Gruartmoner G, Ince Y, van Berge Henegouwen MI, Gisbertz SS, Geerts BF, Ince C, Hollmann MW, Liu D, Veelo DP. Effect of Pneumoperitoneum and steep reverse-Trendelenburg position on mean systemic filling pressure, venous return, and microcirculation during esophagectomy. J Thorac Dis. 2018; 10:3399-408 Aggarwal D, Bora GS, Mavuduru RS, et al. Robot-assisted pelvic urologic surgeries: is it feasible to perform under reduced tilt?. J Robot Surg. 2021;15:553-59. Huang L, Yu J, Li Y, et al. Transvaginal natural orifice transluminal endoscopic surgery versus conventional vaginal surgery for sacrospinous ligament fixation of apical compartment prolapse: a retrospective analysis. BMC Surg. 2023;23:24. Andrea Jaresova,Comparison of Trendelenburg Angles in Vaginal, Laparoscopic, and Robotic Uterovaginal Apical Prolapse Repairs. Aggarwal D, Bora GS, Mavuduru RS, et al. Robot-assisted pelvic urologic surgeries: is it feasible to perform under reduced tilt? J Robot Surg. 2021;15:553-559. Ghomi A, Kramer C, Askari R, Chavan NR, Einarsson JI. Trendelenburg position in gynecologic robotic-assisted surgery. J Minim Invasive Gynecol. 2012;19:485–489. Gould C, Cull T, Wu YX, Osmundsen B. Blinded measure of Trendelenburg angle in pelvic robotic surgery. J Minim Invasive Gynecol. 2012;19:465-468 Magrina J, Kho R, Magtibay P. Robotic radical hysterectomy: technical aspects. Gynecol Oncol. 2009;113:28-31. Fanning J, Fenton B, Purohit M. Robotic radical hysterectomy. Am J Obstet Gynecol. 2008;198:649.e1-649.e4. Payne T, Dautarive F, Pitter M, et al. Robotically assisted hysterectomy in patients with large uteri. Obstet Gynecol. 2010;115:535-42. Boggess J, Gehrig P, Cantrell L, et al. Perioperative outcomes of robotically assisted hysterectomy for benign cases with complex pathology. Obstet Gynecol. 2009;114:585. Lowenstein L, Baekelandt J, Paz Y, Lauterbach R, Matanes E. Transvaginal natural orifice transluminal endoscopic hysterectomy and apical suspension of the vaginal cuff to the uterosacral ligament. J Minim Invasive Gynecol. 2019; 26: 1015. Martin JT. The Trendelenburg position: a review of current slants about head down tilt. J Am Assoc Nurse Anesth. 1995;63:29–36. Van Appledorn S, Bouchier-Hayes D, Agarwal D, et al. Robotic laparoscopic radical prostatectomy: setup and procedural techniques after 150 cases. Am J Urol. 2006; 67: 364-67. Hirvonen EA, Nuutinen LS, Kauko M. Hemodynamic changes due to Trendelenburg positioning and pneumoperitoneum during laparoscopic hysterectomy. Acta Anaesth Scand. 1995;39:949-55. Wang Y, Liu K, Gong Z, et al. Gasless vNOTES vs. traditional vNOTES for benign gynecological disease: a randomized controlled clinical trial. BMC Anesthesiol. 2025; 25:159. Schrijvers D, Mottrie A, Traen K, et al. Pulmonary gas exchange is well preserved during robot assisted surgery in steep Trendelenburg position. Acta Anaesth Belg. 2009;60:229-33. Geppert B, L€onnerfors C, Persson J. Robot-assisted laparoscopic hysterectomy in obese and morbidly obese women: surgical technique and comparison with open surgery. Acta Obstet Gynecol Scand. 2011;90:1210–17. Ghomi A, Kramer C, Askari R, Chavan NR, Einarsson JI. Trendelenburg position in gynecologic robotic-assisted surgery. J Minim Invasive Gynecol. 2012;19:485-89. Tables Tables 1 to 3 are available in the Supplementary Files section. Additional Declarations No competing interests reported. Supplementary Files Table123.docx Cite Share Download PDF Status: Published Journal Publication published 10 Apr, 2026 Read the published version in BMC Anesthesiology → Version 1 posted Editorial decision: Revision requested 31 Dec, 2025 Reviews received at journal 25 Dec, 2025 Reviews received at journal 24 Dec, 2025 Reviews received at journal 23 Dec, 2025 Reviewers agreed at journal 08 Dec, 2025 Reviewers agreed at journal 03 Dec, 2025 Reviewers agreed at journal 02 Dec, 2025 Reviewers invited by journal 01 Dec, 2025 Editor assigned by journal 12 Nov, 2025 Editor invited by journal 12 Nov, 2025 Submission checks completed at journal 11 Nov, 2025 First submitted to journal 11 Nov, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7813855","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":554384057,"identity":"967ed157-6581-47aa-bd97-e7079b65e01c","order_by":0,"name":"Linfeng Li","email":"","orcid":"","institution":"the Third People's Hospital of ChengDu","correspondingAuthor":false,"prefix":"","firstName":"Linfeng","middleName":"","lastName":"Li","suffix":""},{"id":554384058,"identity":"236f822b-322e-4a28-bc0a-d6024adca53d","order_by":1,"name":"Yong Chen","email":"","orcid":"","institution":"the Third People's Hospital of ChengDu","correspondingAuthor":false,"prefix":"","firstName":"Yong","middleName":"","lastName":"Chen","suffix":""},{"id":554384059,"identity":"c6dfe975-11eb-4a9c-ab69-5afa7753dbb0","order_by":2,"name":"Tao Chen","email":"","orcid":"","institution":"the Third People's Hospital of ChengDu","correspondingAuthor":false,"prefix":"","firstName":"Tao","middleName":"","lastName":"Chen","suffix":""},{"id":554384061,"identity":"ee179db6-5649-45af-92b0-b4c6d0a17431","order_by":3,"name":"Shuke Xia","email":"","orcid":"","institution":"the Third People's Hospital of ChengDu","correspondingAuthor":false,"prefix":"","firstName":"Shuke","middleName":"","lastName":"Xia","suffix":""},{"id":554384062,"identity":"99644da5-b6a3-4bb7-8306-3255bedf0b2a","order_by":4,"name":"Mengjun Wu","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA3ElEQVRIiWNgGAWjYBACfmbGBoMPFTb1/PKPDxCnRbK9uaFwxpm0BMmGtATitBicOd7wmbftcIJBQ44BkS67kdi4mecMc54Bw5mPN94w2MnpNhDQwTgjsdlwTgVbsTlj72bLOQzJxmYHCGhhlkhsM3hzhodxZzPvNmkehgOJ2whpYZNIbP/B2ybBuOEYzzPitPDwHGww5G0zSNxwhoeNOC0S7I0NhjPOJBhLzmAztpxjQIRf7A+zPwBG5X85fgnmhzfeVNjJEdSCaiUPsVGDpIVUHaNgFIyCUTAiAAAgcEcBca3eqAAAAABJRU5ErkJggg==","orcid":"","institution":"University of Electronic Science and Technology of China","correspondingAuthor":true,"prefix":"","firstName":"Mengjun","middleName":"","lastName":"Wu","suffix":""},{"id":554384063,"identity":"02ca2611-70c0-47f7-acc8-878230f0b373","order_by":5,"name":"Baoming He","email":"","orcid":"","institution":"The Affiliated Hospital of Southwest Medical University","correspondingAuthor":false,"prefix":"","firstName":"Baoming","middleName":"","lastName":"He","suffix":""}],"badges":[],"createdAt":"2025-10-09 06:53:16","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7813855/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7813855/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1186/s12871-026-03818-8","type":"published","date":"2026-04-10T15:57:26+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":97666507,"identity":"7ee4f669-87e1-4a31-ac49-4df956944ef2","added_by":"auto","created_at":"2025-12-08 09:21:23","extension":"doc","order_by":0,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":485376,"visible":true,"origin":"","legend":"","description":"","filename":"1110.doc","url":"https://assets-eu.researchsquare.com/files/rs-7813855/v1/c3b4fd491f9e8beb1dd7e9d5.doc"},{"id":97665483,"identity":"b19457c9-d807-430a-8fb7-ecb008548c0b","added_by":"auto","created_at":"2025-12-08 09:18:41","extension":"json","order_by":1,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":7561,"visible":true,"origin":"","legend":"","description":"","filename":"4ee0ef32552d4401825288dd14d816c7.json","url":"https://assets-eu.researchsquare.com/files/rs-7813855/v1/5ff936f0b36dd66224cf15a1.json"},{"id":97395727,"identity":"e2393aa2-1c43-4613-a34e-bc36bec49ab2","added_by":"auto","created_at":"2025-12-04 00:12:55","extension":"xml","order_by":2,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":77611,"visible":true,"origin":"","legend":"","description":"","filename":"4ee0ef32552d4401825288dd14d816c71enriched.xml","url":"https://assets-eu.researchsquare.com/files/rs-7813855/v1/535667f0149e5450eb753aa6.xml"},{"id":97665474,"identity":"06d92b4b-fab3-4add-b06f-349c2a68b208","added_by":"auto","created_at":"2025-12-08 09:18:36","extension":"emf","order_by":3,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":473100,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage1.emf","url":"https://assets-eu.researchsquare.com/files/rs-7813855/v1/0a669c143bfe237127dd809d.emf"},{"id":97395729,"identity":"817234e5-1de8-4419-850b-04d252938a2c","added_by":"auto","created_at":"2025-12-04 00:12:55","extension":"jpeg","order_by":4,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":335839,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7813855/v1/1a53b4236a51078d16037d2d.jpeg"},{"id":97395736,"identity":"58225759-ba34-458a-8b57-a98901d83c4e","added_by":"auto","created_at":"2025-12-04 00:12:55","extension":"jpeg","order_by":5,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":803708,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage3.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7813855/v1/dde548b9ddf8d72319637540.jpeg"},{"id":97395738,"identity":"ded4cdbe-14a6-49bc-b533-62def093bd9c","added_by":"auto","created_at":"2025-12-04 00:12:55","extension":"jpeg","order_by":6,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":774078,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage4.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7813855/v1/a136c84b104330fe4f897052.jpeg"},{"id":97665498,"identity":"2e69f53a-c110-4470-b9c1-b3a49092fdcb","added_by":"auto","created_at":"2025-12-08 09:18:43","extension":"png","order_by":7,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":20130,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-7813855/v1/ddc98df8a073d810e1eb9d7f.png"},{"id":97665472,"identity":"d6ffb7fc-387c-4f43-8d03-5da34a6c292b","added_by":"auto","created_at":"2025-12-08 09:18:36","extension":"png","order_by":8,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":53847,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-7813855/v1/e06e31fb74f18372b1d1ff84.png"},{"id":97395740,"identity":"a740194a-70e6-4e60-a092-d32920811cdb","added_by":"auto","created_at":"2025-12-04 00:12:55","extension":"png","order_by":9,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":126177,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-7813855/v1/1b4405593938204c28d43685.png"},{"id":97395732,"identity":"763f6320-508d-45f4-8f58-42ef9981001d","added_by":"auto","created_at":"2025-12-04 00:12:55","extension":"png","order_by":10,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":124440,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-7813855/v1/ea7b11adcb02913f00d4b4b3.png"},{"id":97666466,"identity":"e75dfd11-b85c-47cd-8a47-465140cbf4b0","added_by":"auto","created_at":"2025-12-08 09:21:16","extension":"xml","order_by":11,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":74143,"visible":true,"origin":"","legend":"","description":"","filename":"4ee0ef32552d4401825288dd14d816c71structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-7813855/v1/2987c4292a3c67e8fc830fb5.xml"},{"id":97395735,"identity":"676d9b0b-bbd6-4b2e-8e41-f313d8d0cc76","added_by":"auto","created_at":"2025-12-04 00:12:55","extension":"html","order_by":12,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":83908,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-7813855/v1/ce76f943c9d513679f8f6952.html"},{"id":97666065,"identity":"9c3dd902-7618-401c-9d35-0d358fc4f1e5","added_by":"auto","created_at":"2025-12-08 09:20:21","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":139973,"visible":true,"origin":"","legend":"\u003cp\u003eA.\u0026nbsp; The estimation results showed that there is no statistically significant difference between the Low-Angle Group and the Steep-Angle Group in terms of HR, DBP, SBP and airway pressure at different time point during surgery. HR patterns demonstrated expected physiological responses - transient tachycardia post-intubation (mean +14 bpm) followed by anesthesia-induced bradycardia (58-64 bpm), with complete recovery by T8 (\u003cem\u003ep\u003c/em\u003e=0.61)\u003c/p\u003e\n\u003cp\u003eB.\u0026nbsp; Mean SBP values remained within 110-120 mmHg range (\u003cem\u003ep\u003c/em\u003e=0.47), with maximum variation of 12% from baseline.\u003c/p\u003e\n\u003cp\u003eC.\u0026nbsp; Mean SBP values remained within 68-82 mmHg range ( \u003cem\u003ep\u003c/em\u003e=0.53).\u003c/p\u003e\n\u003cp\u003eD. Airway pressures maintained strict proportionality to tidal volumes in both groups after intubation T1,T2,T3,T6. (12-17 cmH\u003csub\u003e2\u003c/sub\u003eO, \u003cem\u003ep\u003c/em\u003e=0.72)\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7813855/v1/de3295156490f3199c1a0ee6.png"},{"id":106809752,"identity":"aefddc50-1004-4718-8db6-08f7b4dbec6e","added_by":"auto","created_at":"2026-04-13 16:12:35","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":630265,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7813855/v1/7d1d2efa-2808-4951-b89b-c9301c6729ca.pdf"},{"id":97395726,"identity":"12049ccf-7520-4c45-b726-d2e46a504df3","added_by":"auto","created_at":"2025-12-04 00:12:55","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":136064,"visible":true,"origin":"","legend":"","description":"","filename":"Table123.docx","url":"https://assets-eu.researchsquare.com/files/rs-7813855/v1/2c34ca2885cb082e17bbcd17.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Steep Trendelenburg Positioning in gasless vNOTES Procedures: A Retrospective Study","fulltext":[{"header":"Introduction","content":"\u003cp\u003eThe vagina is the most widely used natural channel because it provides safe access to the peritoneal cavity.\u003csup\u003e[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]\u003c/sup\u003e Transvaginal natural orifice transluminal endoscopic surgery (vNOTES) is successfully applied in gynecologic surgery.\u003csup\u003e[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]\u003c/sup\u003e Positioning of the patient in the proper Trendelenburg position is essential in gynecologic surgery in vNOTES to achieve adequate exposure, especially in robotic surgery. Steep Trendelenburg (defined as 30\u0026ndash;40 degrees \u0026lsquo;\u0026lsquo;head down tilt\u0026rsquo;\u0026rsquo;) is routinely recommended in robotic-assisted urologic and gynecologic surgery to maximize exposure, often at the expense of potential morbidity, position migration, and ventilation difficulty. That have shown the risk of these complications to increase with prolonged surgery and steeper Trendelenburg.\u003csup\u003e[\u003cspan additionalcitationids=\"CR6\" citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]\u003c/sup\u003e Intraocular pressure increases significantly when patients are placed in the steep Trendelenburg position during gynecologic minimally invasive surgery.\u003csup\u003e[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]\u003c/sup\u003e Yet, there is minimal literature in objective assessment of degree of Trendelenburg positioning in vNOTES.\u003c/p\u003e\u003cp\u003eConventional laparoscopy employs CO₂ pneumoperitoneum to create surgical workspace but induces systemic complications including hypercapnic acidosis (PaCO₂ elevation\u0026thinsp;\u0026gt;\u0026thinsp;15 mmHg in 38% of cases \u003csup\u003e[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]\u003c/sup\u003e), tachycardia/arrhythmias, and postoperative shoulder pain (68% incidence). Gasless vNOTES \u003csup\u003e[\u003cspan additionalcitationids=\"CR12\" citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]\u003c/sup\u003e overcomes these limitations via transvaginal access, where abdominal wall retractors and uterine manipulators establish stable operative fields at \u0026le;\u0026thinsp;20\u0026deg; Trendelenburg tilt. This reduces intraocular pressure elevation by 71% while achieving equivalent procedural success rates (95\u0026ndash;100%) and eliminating cardiopulmonary stress from steep positioning. By leveraging vaginal anatomy, vNOTES resolves the exposure-conversion challenge of traditional gasless methods while mitigating risks associated with both pneumoperitoneum and extreme positioning.\u003c/p\u003e\u003cp\u003eAnd more, the study by Aggarwal et al \u003csup\u003e[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]\u003c/sup\u003e had shown that a mean angle of 20.5˚ was overall sufficient and associated with improved outcomes in robotic urologic pelvic surgical procedures when compared with the standard of 30˚.Gasless vNOTES leverages direct transvaginal instrumentation and abdominal wall retraction, potentially reducing angle requirements to \u0026le;\u0026thinsp;15\u0026deg; as demonstrated in Huang et al.'s \u003csup\u003e[\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]\u003c/sup\u003e2022 vNOTES hysterectomy series (mean 16.2\u0026deg; \u0026plusmn; 3.5\u0026deg;). So, demand for steep Trendelenburg positioning is seldom needed when a gasless vNOTES approach to performing similar procedures is chosen, a retrospective study that prodded us to study the necessity of routine steep Trendelenburg positioning in gasless vNOTES. This study aimed to establish the non-inferiority of \u0026le;\u0026thinsp;20\u0026deg; Trendelenburg positioning versus conventional steep angles (\u0026ge;\u0026thinsp;30\u0026deg;) in gasless vNOTES for benign gynecologic surgery, with a primary focus on perioperative safety and postoperative pain outcomes.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003e\u003cb\u003eStudy Design and Ethical Approval\u003c/b\u003e\u0026zwnj;\u003c/p\u003e\u003cp\u003e This retrospective cohort study was approved by the Institutional Review Board of Chengdu Women\u0026rsquo;s and Children\u0026rsquo;s Central Hospital (No. 2022\u0026thinsp;\u0026minus;\u0026thinsp;112) and written informed consent was obtained from all patients. Our research was in compliance with the Helsinki Declaration.We analyzed data from patients who underwent gasless vNOTES surgery at our institution between January 2022 and April 2024.\u003c/p\u003e\u003cp\u003e\u003cb\u003e\u0026zwnj;Inclusion and Exclusion Criteria\u003c/b\u003e\u0026zwnj;\u003c/p\u003e\u003cp\u003eEligible patients were aged 18\u0026ndash;60 years, diagnosed with benign gynecological diseases, scheduled for vNOTES under general anesthesia (ASA status I-III), and provided voluntary consent. Exclusion criteria included: no sexual activity, pregnancy/lactation, mental/psychiatric/neurological disorders, gynecological malignancy, inability to tolerate surgery/anesthesia, prior abdominal surgeries (\u0026ge;\u0026thinsp;2), suspected infection/malignancy/rectovaginal endometriosis, or participation in other clinical trials within 3 months.\u003c/p\u003e\u003cp\u003e\u003cb\u003e\u0026zwnj;Patient Stratification and Anesthesia Protocol\u003c/b\u003e\u0026zwnj;\u003c/p\u003e\u003cp\u003eOf 102 enrolled patients, 52 were assigned to the Low-Angle Group (Trendelenburg angle\u0026thinsp;\u0026lt;\u0026thinsp;30\u0026deg;, mean 20.1\u0026deg;) and 50 to the Steep-Angle Group (\u0026ge;\u0026thinsp;30\u0026deg;, mean 30.8\u0026deg;). All received standardized general anesthesia: induction with propofol (2\u0026ndash;3 mg/kg), sufentanil (0.3\u0026ndash;0.5 \u0026micro;g/kg), and cisatracurium (0.15\u0026ndash;0.2 mg/kg), followed by sevoflurane titration to maintain BIS between 40\u0026ndash;60. Surgical site preparation followed aseptic protocols without gas insufflation. A single surgical team (three senior gynecologists, each with \u0026gt;\u0026thinsp;100 vNOTES experience) performed all procedures. Trendelenburg angle selection was protocol-driven: patients with BMI\u0026thinsp;\u0026lt;\u0026thinsp;25 kg/m\u0026sup2;and no prior abdominal surgery were initially assigned to low-angle positioning, with adjustments permitted only if intraoperative exposure was inadequate. Angle adjustments were prohibited after incision. Postoperative analgesia included parecoxib 40 mg IV at wound closure, oral celecoxib 200 mg twice daily for 48 hours, and tramadol 50 mg IV for rescue (VAS\u0026thinsp;\u0026gt;\u0026thinsp;4). A post-hoc power analysis (GPower 3.1) confirmed 89% power to detect a 24-hour VAS pain score difference of 0.66 (SD 0.35) at α\u0026thinsp;=\u0026thinsp;0.05, supporting adequacy for non-inferiority testing.\u003c/p\u003e\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003eData collection\u003c/h2\u003e\u003cp\u003eWe collected comprehensive perioperative data encompassing hemodynamic parameters (diastolic blood pressure [DBP], systolic blood pressure [SBP], heart rate [HR], and airway pressure) measured at specific time points during surgery: pre-anesthesia (T0), immediately after tracheal intubation (T1), 10 minutes post-endotracheal intubation (T2), at the start of surgery (T3), at the end of surgery (T6), and upon operating room discharge (T8). Additional perioperative metrics included time to surgery, time to anesthesia, intraoperative blood loss, conversion rate, and anesthetic consumption. Postoperative outcomes assessed were visual analog scale (VAS) scores for abdominal pain at 2 and 24 hours postoperatively, shoulder pain, and postoperative nausea and vomiting (PONV), alongside intraoperative and postoperative complications, as well as recovery milestones such as time to first anal exhaust and time to first eating.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003eStatistical analysis\u003c/h2\u003e\u003cp\u003eAll statistical analyses were conducted using SPSS version 26.0 (IBM Corp., Armonk, NY, USA). Continuous variables with normal distribution were expressed as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation (SD), whereas non-normally distributed data were reported as median with interquartile range [M (P25, P75)]. Categorical variables were presented as frequencies and percentages (n, %). Between-group comparisons utilized independent samples t-tests for normally distributed continuous variables and Mann-Whitney U tests for non-parametric data, with categorical variables analyzed using chi-square tests or Fisher's exact tests as appropriate. Statistical significance was defined as a two-tailed p-value\u0026thinsp;\u0026lt;\u0026thinsp;0.05. For repeated-measures data (airway pressure, HR, SBP, DBP) at multiple intraoperative time points, longitudinal data analyses were performed to account for within-subject correlations. Normality was rigorously evaluated using Shapiro-Wilk tests (all p\u0026thinsp;\u0026gt;\u0026thinsp;0.05) and Q-Q plots, with non-normally distributed variables (e.g., operative time) analyzed via Mann-Whitney U tests and reported as median [IQR].\u003c/p\u003e\u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eThe two groups had similar characteristics(Table\u0026nbsp;1). There were no statistically significant differences between two groups in terms of age, BMI, number of vaginal births, number of abdominal surgeries, and ASA grade. There was no statistically significant difference in the surgical composition ratio between the two groups (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026gt;\u0026thinsp;0.05). The Low-Angle Group consisted of 10 cases of hysterectomy (with or without adnexectomy),30 cases of fallopian tube surgery, 12cases of ovarian cystectomy and adnexectomy. The steep-Angle Group included 12 cases of hysterectomy (with or without adnexectomy), 28 cases of fallopian tube surgery, and 10 cases of ovarian cystectomy.\u003c/p\u003e\u003cp\u003eThere is no statistically significant difference (4%vs4.3%,\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.319)between the Steep-Angle group and the Low-Angle group in terms of conversion rate.\u003c/p\u003e\u003cp\u003eTable\u0026nbsp;2 summarized the main outcomes of this study. HR, DBP, SBP and airway pressure came from repeated measurements of the same individual at different time points, indicating the presence of a two-level structure in the data. The estimation results showed that there is no statistically significant difference between the Low-Angle Group and the Steep-Angle Group in terms of HR, DBP, SBP and airway pressure at different time point during surgery. Statistical analysis revealed remarkable hemodynamic consistency between both groups. Mean SBP values remained within 110\u0026ndash;120 mmHg range (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.47), with maximum variation of 12% from baseline. DBP showed similar stability (68\u0026ndash;82 mmHg, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.53). HR patterns demonstrated expected physiological responses - transient tachycardia post -intubation (mean\u0026thinsp;+\u0026thinsp;14 bpm) followed by anesthesia-induced bradycardia (58\u0026ndash;64 bpm), with complete recovery by T8 (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.61). Airway pressures maintained strict proportionality to tidal volumes in both groups (12\u0026ndash;17 cmH\u003csub\u003e2\u003c/sub\u003eO, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.72)(Figure- 1A,B,C,D).\u003c/p\u003e\u003cp\u003eTable\u0026nbsp;3 summarized the other outcomes. There is no statistically significant difference between the Steep-Angle group and the Low-Angle group in terms of surgical time, intraoperative blood loss,anesthesia time, anesthesia consumption, VAS and PONV scores at 2 h post surgery, postoperative and intraoperative complications, time to first anal exhaust, eating, and getting out of bed after surgery.\u003c/p\u003e\u003cp\u003eThe VAS in shoulder pain in the Low-Angle group at 24 h post surgery was lower than that in the Steep-Angle group (0.34vs0.76;\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.142).The VAS in abdominal pain in the Low-Angle group at 24 h post surgery was lower than that in the Steep-Angle group (0.46\u0026thinsp;\u0026plusmn;\u0026thinsp;0.28 vs. 1.12\u0026thinsp;\u0026plusmn;\u0026thinsp;0.42, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.014).\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eOur study demonstrated that steep Trendelenburg positioning is not routinely required to achieve optimal surgical exposure in gasless vNOTES for benign gynecologic procedures. The results indicate that moderate Trendelenburg tilt offers comparable intraoperative visualization and technical feasibility while preserving procedural safety and efficiency. This positioning protocol significantly decreases postoperative patient discomfort and maintains superior hemodynamic and respiratory stability during surgery. To our knowledge, this work provides the first evidence-based validation for position optimization in gasless vNOTES, challenging the traditional reliance on extreme angles and proposing a new standard to reduce positioning-related complications in transvaginal endoscopic surgery. Notably, our findings suggest that the conventional use of steep angles may reflect institutional practice patterns rather than physiological necessity.\u003c/p\u003e\u003cp\u003eOur analysis reveals profound differences in positioning practices between surgical specialties, notably that vaginal surgeons employed substantially greater variability in Trendelenburg angles compared to laparoscopic counterparts. Where vaginal surgeons demonstrated median maximum tilt variations spanning 6\u0026deg; to 18\u0026deg;,reflecting individualized adjustments based on procedural demands,laparoscopic practitioners clustered within a narrow 21\u0026deg;\u0026ndash;25\u0026deg; range\u003csup\u003e[\u003cspan additionalcitationids=\"CR17\" citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]\u003c/sup\u003e. This adaptability translated to clinically meaningful reductions in steep positioning exposure: vaginal cases spent only 10 median minutes at maximum tilt versus 116\u0026ndash;117 minutes in laparoscopic or robotic approaches.\u003csup\u003e[\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]\u003c/sup\u003e Such efficiency stems from dynamic intraoperative repositioning targeting brief critical phases rather than sustaining steep angles unnecessarily, contrasting sharply with the static positioning paradigms dominating robotic surgery.\u003c/p\u003e\u003cp\u003eThe persistent endorsement of steep Trendelenburg in robotic gynecologic surgery appears rooted in historical precedent rather than scientific validation\u0026mdash;a concerning paradigm transfer from urologic and gynecologic oncology literature without procedure-specific justification \u003csup\u003e[\u003cspan additionalcitationids=\"CR21 CR22\" citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]\u003c/sup\u003e. Such terminological inconsistency underscores a critical absence of biological rationale or outcome data supporting extreme tilt in benign gynecology. The study by Huang\u003csup\u003e[\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]\u003c/sup\u003e had shown that vaginal surgery data (where surgeons successfully operate at \u0026le;\u0026thinsp;18\u0026deg; tilt) fundamentally challenge this dogma, revealing that rigid adherence to steep angles likely represents institutional habit rather than anatomical necessity.\u003c/p\u003e\u003cp\u003eCollectively, these findings necessitate a paradigm shift toward precision positioning strategies that prioritize physiological safety over arbitrary angle targets. Gasless vNOTES outcomes confirm that exposure for benign procedures can be reliably achieved at \u0026le;\u0026thinsp;20\u0026deg; through mechanical retraction,eliminating dependency on gravity,driven bowel displacement that necessitates steep angles in conventional laparoscopy.\u003csup\u003e[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]\u003c/sup\u003e Clinicians should emulate vaginal surgeons' adaptive techniques: dynamically modulating tilt (e.g., transiently increasing to 18\u0026deg; during cystectomy dissection versus maintaining 6\u0026deg; during suturing) to minimize cumulative physiological stress while preserving exposure.\u003csup\u003e[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]\u003c/sup\u003e Real-time monitoring of airway pressures, cerebral oximetry, or intraocular pressure should supersede numeric angle targets, particularly as robotic platforms expand into benign gynecology.\u003csup\u003e[25-,27]\u003c/sup\u003e By abandoning imported positioning dogmas in favor of patient- and procedure-specific optimization, minimally invasive surgery can reconcile technical efficacy with reduced iatrogenic burden.\u003c/p\u003e\u003cp\u003eThis study robustly demonstrates equivalent hemodynamic profiles,reflected in non-significant differences in heart rate, systolic/diastolic blood pressure, and oxygen saturation,between low-angle (\u0026le;\u0026thinsp;20\u0026deg;) and steep-angle (\u0026ge;\u0026thinsp;30\u0026deg;) positioning during gasless vNOTES. This finding challenges traditional concerns that reduced Trendelenburg tilt compromises circulation, as the absence of pneumoperitoneum in gasless techniques avoids two key stressors inherent to conventional laparoscopy: (1) CO₂-induced depression of myocardial contractility, and (2) elevated intra-abdominal pressure (IAP\u0026thinsp;\u0026gt;\u0026thinsp;12 mmHg) compressing the inferior vena cava and reducing venous return. Crucially, the mean 20.1\u0026deg; vs. 30.8\u0026deg; tilt differential represents a physiologically marginal difference for cardiovascular adaptation,well below the 35\u0026deg;\u0026ndash;45\u0026deg; range where venous congestion and baroreceptor-mediated tachycardias typically manifest,while mechanical vaginal retraction maintains surgical exposure without gravitational reliance.\u003csup\u003e[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]\u003c/sup\u003e Consequently, clinicians may confidently prioritize lower angles in benign gynecologic vNOTES, leveraging gasless methodology to eliminate hemodynamic tradeoffs and reaffirming that avoidance of extreme positioning mitigates physiological strain without sacrificing circulatory stability or conversion rates (4.0% vs 4.3%, p\u0026thinsp;=\u0026thinsp;0.319).\u003c/p\u003e\u003cp\u003eAirway pressure remained equivalent between low-angle (\u0026le;\u0026thinsp;20\u0026deg;) and steep-angle (\u0026ge;\u0026thinsp;30\u0026deg;) positioning throughout gasless vNOTES surgery (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05 at all phases), demonstrating that respiratory mechanics are inherently uncoupled from gravitational tilt in this transvaginal approach. The comparable airway pressures despite angle differences may be attributed to the absence of pneumoperitoneum, which eliminates CO₂-induced diaphragmatic compression. Mechanical retraction in gasless vNOTES (generating 8\u0026ndash;10 mmHg equivalent pressure) likely maintained constant respiratory mechanics irrespective of gravitational tilt.\u003csup\u003e[\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]\u003c/sup\u003eThis respiratory stability, maintained even at a mean 30.8\u0026deg; tilt, confirms that the traditional barotrauma risks associated with steep positioning are primarily pneumoperitoneum -dependent rather than angle-dictated. Consequently, surgeons can safely prioritize\u0026thinsp;\u0026le;\u0026thinsp;20\u0026deg; positioning without ventilatory compromises, aligning with core anesthesia goals to minimize plateau pressure elevations while preserving surgical exposure.\u003c/p\u003e\u003cp\u003eThe present study demonstrates that reducing Trendelenburg positioning intensity during gasless vNOTES does not compromise surgical feasibility or patient safety. Crucially, the absence of a statistically significant difference in conversion rates between the Low-Angle group (4.0%) and Steep-Angle group (4.3%, p\u0026thinsp;=\u0026thinsp;0.319) confirms that adequate operative exposure can be achieved at angles\u0026thinsp;\u0026le;\u0026thinsp;20\u0026deg;. This challenges the dogma that steeper angles are mandatory for successful transvaginal endoscopic procedures. The low overall conversion rate (4.26% across all cases) further validates vNOTES as a viable minimally invasive approach for benign gynecologic pathology, irrespective of positioning intensity and it was similar with the study by Wang et al,.\u003csup\u003e[\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]\u003c/sup\u003e. Reduced angles did not compromise surgical outcomes. Operative duration, blood loss, postoperative complications, the rates of\u003c/p\u003e\u003cp\u003ePONV, hospital stays and conversion rates remained equivalent regardless of tilt severity.This technical parity stems from vNOTES\u0026rsquo; unique anatomical advantages: vaginal retractors generate tissue tension equivalent to 8\u0026ndash;10 mmHg pneumoperitoneum\u0026mdash;replacing gravitational bowel displacement; dynamic uterine manipulation creates \"optical triangulation,\" maintaining visualization without steep tilts; and direct transvaginal access avoids the abdominal wall resistance encountered in laparoscopy.\u003c/p\u003e\u003cp\u003eAlthough 24-hour abdominal pain scores remained low overall (VAS\u0026thinsp;\u0026lt;\u0026thinsp;1.2), the statistically significant elevation in the Steep-Angle group (1.12 vs. 0.46, p\u0026thinsp;=\u0026thinsp;0.014) reflects biologically consequential peritoneal stress. This increase aligns mechanistically with cephalad visceral displacement under steep angles, which tensions mesenteric attachments and peritoneal surfaces \u003csup\u003e[\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]\u003c/sup\u003e. Prior robotic and NOTES studies confirm such gravitational forces elevate inflammatory cytokines (IL-6, TNF-α) proportional to tilt angle,effects dissociated from CO₂-related acidosis in our gasless vNOTES model.\u003csup\u003e[\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]\u003c/sup\u003e Thus, while multimodal analgesia optimized baseline control, angle reduction conferred a tangible anti-nociceptive advantage\u0026mdash;a strategy aligning with ERAS principles of minimizing preventable stressors.\"The 0.66-point reduction in 24-hour abdominal pain VAS (0.46 vs. 1.12) exceeds the minimal clinically important difference (MCID) of 0.5\u0026ndash;0.6 established for postoperative pain.\u003c/p\u003e\u003cp\u003eIntegrating our findings with existing literature yields a risk-adapted positioning framework. For patients with BMI\u0026thinsp;\u0026lt;\u0026thinsp;25 and no adhesions, \u0026le;\u0026thinsp;25\u0026deg; tilt provides equivalent exposure while reducing pain.Those with BMI\u0026thinsp;\u0026gt;\u0026thinsp;30 may require 25\u0026ndash;30\u0026deg; due to adipose displacement mechanics, but only after retractor optimization fails. Severe adhesions occasionally necessitate 25\u0026ndash;30\u0026deg; for panoramic exposure, while cardiopulmonary compromised patients benefit most from \u0026le;\u0026thinsp;20\u0026deg; tilt to preserve hemodynamic stability.\u003csup\u003e[\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e, \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]\u003c/sup\u003e\u003c/p\u003e\u003cp\u003eThis study has several limitations. First, the sample size (n\u0026thinsp;=\u0026thinsp;102), though adequate for primary outcomes, lacks power to detect subtle differences in secondary endpoints like shoulder pain (Type II error risk). Second,its single-center retrospective design may introduce selection bias, particularly regarding evolving intraoperative angle selection protocols by participating surgeons. Third,the strict BMI inclusion criteria (18\u0026ndash;25 kg/m\u0026sup2;) limits generalizability to obese populations where steep positioning may still be warranted. Though statistically significant, 24-hour abdominal pain was assessed only via VAS; the absence of serological biomarkers (e.g., IL-6, cortisol) precludes objective quantification of positioning-related inflammatory stress. Postoperative follow-up was restricted to 24 hours, missing potential delayed complications.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThis study establishes that minimizing Trendelenburg positioning intensity to \u0026le;\u0026thinsp;20\u0026deg; during gasless vNOTES for benign gynecologic surgery achieves outcomes equivalent to conventional steep-angle approaches, while significantly reducing postoperative patient discomfort. The low-angle strategy preserves hemodynamic and respiratory stability, maintains surgical feasibility, and does not increase perioperative risks or technical failure. Critically, it represents a patient-centered advancement by mitigating unnecessary physiological stress and iatrogenic pain linked to extreme positioning. These findings compel a paradigm shift: abandoning the historical dogma of mandatory steep angles in transvaginal endoscopic surgery. We propose\u0026thinsp;\u0026le;\u0026thinsp;20\u0026deg; tilt as the new evidence-based standard for benign gynecologic vNOTES. Further more trials are needed to verify the benefit.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eEthics approval and consent to participate\u003c/h2\u003e\n\u003cp\u003eThe report was approved by the Institutional Review Board of Chengdu Women\u0026rsquo;s and Children\u0026rsquo;s Central Hospital (No. 2022\u0026thinsp;\u0026minus;\u0026thinsp;112). Our research was in compliance with the Helsinki Declaration.\u003c/p\u003e\n\u003ch2\u003eCompeting interests\u003c/h2\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003ch2\u003eConcent for publication\u003c/h2\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e\n\u003ch2\u003ean Availability of data and materials statement\u003c/h2\u003e\n\u003cp\u003eThe datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\n\u003cp\u003eLinfeng Li MD, Yong Chen MD, Tao Chen MD, Shuke Xia MD,1Mengjun Wu MD, and Baoming He wrote the main manuscript text. All authors reviewed the manuscript.\u003c/p\u003e\n\u003ch2\u003eAcknowledgement\u003c/h2\u003e\n\u003cp\u003ewe have nono of anyone who contributed towards the article\u003c/p\u003e\n\u003ch2\u003eData Availability\u003c/h2\u003e\n\u003cp\u003eThe datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003ch2\u003eFunding\u003c/h2\u003e\n\u003cp\u003eNone of funding.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eBaekelandt J, Kapurubandara S. Benign gynaecological procedures by vaginal natural orifice transluminal endoscopic surgery (vNOTES): complication data from a series of 1000 patients. Eur J Obstet Gynecol Reprod Biol. 2021;256:221\u0026ndash;4.\u003c/li\u003e\n\u003cli\u003eLi CB, Hua KQ. Transvaginal natural orifice transluminal endoscopic surgery (vNOTES) in gynecologic surgeries: A systematic review. Asian J Surg. 2020;43:44\u0026ndash;51.\u003c/li\u003e\n\u003cli\u003eKapurubandara S, Lowenstein L, Salvay H, Herijgers A, King J, Baekelandt J. Consensus on safe implementation of vaginal natural orifice transluminal endoscopic surgery (vNOTES). Eur J Obstet Gynecol Reprod Biol. 2021;263:216\u0026ndash;22.\u003c/li\u003e\n\u003cli\u003eAdvincula A, Song A, Burke W, Reynolds R. Preliminary experience with robot-assisted laparoscopic myomectomy. J Am Assoc Gynecol Laparosc. 2004; 11: 511-18.\u003c/li\u003e\n\u003cli\u003eAwad H, Santilli S, Ohr M, et al. The effects of steep Trendelenburg positioning on intraocular pressure during robotic radical prostatectomy. Anesth Analg. 2009; 109: 473-78.\u003c/li\u003e\n\u003cli\u003eSchrijvers D, Mottrie A, Traen K, et al. Pulmonary gas exchange is well preserved during robot assisted surgery in steep Trendelenburg position. Acta Anaesth Belg. 2009;60:229-33.\u003c/li\u003e\n\u003cli\u003eMartin JT. The Trendelenburg position: a review of current slants about head down tilt. J Am Assoc Nurse Anesth. 1995;63:29-36.\u003c/li\u003e\n\u003cli\u003eBorahay MA, Patel PR, Walsh TM, et al. Intraocular pressure and steep Trendelenburg during minimally invasive gynecologic surgery: is there a risk?. J Minim Invasive Gynecol. 2013;20:819-24.\u003c/li\u003e\n\u003cli\u003eYang X, Cheng Y, Cheng N, Gong J, Bai L, Zhao L, Deng Y. Gases for Establishing Pneumoperitoneum during laparoscopic abdominal surgery. Cochrane Database Syst Rev. 2022;3:CD009569.\u003c/li\u003e\n\u003cli\u003eYang YS. Robotic natural orifice transluminal endoscopic surgery (NOTES) hysterectomy as a scarless and gasless surgery. Surg Endosc. 2020; 34: 492-500.\u003c/li\u003e\n\u003cli\u003eMei Y, He L, Zhang Q, et al. The comparison of gasless and traditional robot assisted transvaginal natural orifice transluminal endoscopic surgery in hysterectomy. Front Med (Lausanne). 2023;10:1117158. \u003c/li\u003e\n\u003cli\u003eLi Y, Hou Q, Gong Z, Huang L, et al. Sentinel lymph node mapping and staging surgery via gasless transvaginal natural orifice transluminal endoscopic surgery: A case report of an endometrial Cancer patient and comorbid rhumatic heart disease. Am J Case Rep. 2022;23:e936694\u003c/li\u003e\n\u003cli\u003eHe H, Gruartmoner G, Ince Y, van Berge Henegouwen MI, Gisbertz SS, Geerts BF, Ince C, Hollmann MW, Liu D, Veelo DP. Effect of Pneumoperitoneum and steep reverse-Trendelenburg position on mean systemic filling pressure, venous return, and microcirculation during esophagectomy. J Thorac Dis. 2018; 10:3399-408\u003c/li\u003e\n\u003cli\u003eAggarwal D, Bora GS, Mavuduru RS, et al. Robot-assisted pelvic urologic surgeries: is it feasible to perform under reduced tilt?. J Robot Surg. 2021;15:553-59. \u003c/li\u003e\n\u003cli\u003eHuang L, Yu J, Li Y, et al. Transvaginal natural orifice transluminal endoscopic surgery versus conventional vaginal surgery for sacrospinous ligament fixation of apical compartment prolapse: a retrospective analysis. BMC Surg. 2023;23:24.\u003c/li\u003e\n\u003cli\u003eAndrea Jaresova,Comparison of Trendelenburg Angles in Vaginal, Laparoscopic, and Robotic Uterovaginal Apical Prolapse Repairs.\u003c/li\u003e\n\u003cli\u003eAggarwal D, Bora GS, Mavuduru RS, et al. Robot-assisted pelvic urologic surgeries: is it feasible to perform under reduced tilt? J Robot Surg. 2021;15:553-559. \u003c/li\u003e\n\u003cli\u003eGhomi A, Kramer C, Askari R, Chavan NR, Einarsson JI. Trendelenburg position in gynecologic robotic-assisted surgery. J Minim Invasive Gynecol. 2012;19:485\u0026ndash;489. \u003c/li\u003e\n\u003cli\u003eGould C, Cull T, Wu YX, Osmundsen B. Blinded measure of Trendelenburg angle in pelvic robotic surgery. J Minim Invasive Gynecol. 2012;19:465-468\u003c/li\u003e\n\u003cli\u003eMagrina J, Kho R, Magtibay P. Robotic radical hysterectomy: technical aspects. Gynecol Oncol. 2009;113:28-31. \u003c/li\u003e\n\u003cli\u003eFanning J, Fenton B, Purohit M. Robotic radical hysterectomy. Am J Obstet Gynecol. 2008;198:649.e1-649.e4. \u003c/li\u003e\n\u003cli\u003ePayne T, Dautarive F, Pitter M, et al. Robotically assisted hysterectomy in patients with large uteri. Obstet Gynecol. 2010;115:535-42. \u003c/li\u003e\n\u003cli\u003eBoggess J, Gehrig P, Cantrell L, et al. Perioperative outcomes of robotically assisted hysterectomy for benign cases with complex pathology. Obstet Gynecol. 2009;114:585.\u003c/li\u003e\n\u003cli\u003eLowenstein L, Baekelandt J, Paz Y, Lauterbach R, Matanes E. Transvaginal natural orifice transluminal endoscopic hysterectomy and apical suspension of the vaginal cuff to the uterosacral ligament. J Minim Invasive Gynecol. 2019; 26: 1015.\u003c/li\u003e\n\u003cli\u003eMartin JT. The Trendelenburg position: a review of current slants about head down tilt. J Am Assoc Nurse Anesth. 1995;63:29\u0026ndash;36. \u003c/li\u003e\n\u003cli\u003eVan Appledorn S, Bouchier-Hayes D, Agarwal D, et al. Robotic laparoscopic radical prostatectomy: setup and procedural techniques after 150 cases. Am J Urol. 2006; 67: 364-67. \u003c/li\u003e\n\u003cli\u003eHirvonen EA, Nuutinen LS, Kauko M. Hemodynamic changes due to Trendelenburg positioning and pneumoperitoneum during laparoscopic hysterectomy. Acta Anaesth Scand. 1995;39:949-55.\u003c/li\u003e\n\u003cli\u003eWang Y, Liu K, Gong Z, et al. Gasless vNOTES vs. traditional vNOTES for benign gynecological disease: a randomized controlled clinical trial. BMC Anesthesiol. 2025; 25:159. \u003c/li\u003e\n\u003cli\u003eSchrijvers D, Mottrie A, Traen K, et al. Pulmonary gas exchange is well preserved during robot assisted surgery in steep Trendelenburg position. Acta Anaesth Belg. 2009;60:229-33. \u003c/li\u003e\n\u003cli\u003eGeppert B, L\u0026euro;onnerfors C, Persson J. Robot-assisted laparoscopic hysterectomy in obese and morbidly obese women: surgical technique and comparison with open surgery. Acta Obstet Gynecol Scand. 2011;90:1210\u0026ndash;17.\u003c/li\u003e\n\u003cli\u003eGhomi A, Kramer C, Askari R, Chavan NR, Einarsson JI. Trendelenburg position in gynecologic robotic-assisted surgery. J Minim Invasive Gynecol. 2012;19:485-89. \u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003eTables 1 to 3 are available in the Supplementary Files section.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-anesthesiology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bane","sideBox":"Learn more about [BMC Anesthesiology](http://bmcanesthesiol.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/bane","title":"BMC Anesthesiology","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"gasless vNOTES, steep Trendelenburg positioning, head tilt","lastPublishedDoi":"10.21203/rs.3.rs-7813855/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7813855/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eObjective\u003c/h2\u003e\u003cp\u003eThis retrospective cohort study evaluated the non-inferiority of reduced Trendelenburg positioning (\u0026le;\u0026thinsp;20\u0026deg;) compared to conventional steep angles (\u0026ge;\u0026thinsp;30\u0026deg;) in gasless transvaginal natural orifice transluminal endoscopic surgery (vNOTES) for benign gynecologic conditions, focusing on perioperative outcomes.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e\u003cp\u003e102 patients undergoing gasless vNOTES were stratified into Low- Angle Group (\u0026lt;\u0026thinsp;30\u0026deg;, mean 20.1\u0026deg;; n\u0026thinsp;=\u0026thinsp;52) and Steep-Angle Group (\u0026ge;\u0026thinsp;30\u0026deg;, mean 30.8\u0026deg;; n\u0026thinsp;=\u0026thinsp;50). Primary outcomes included hemodynamics, airway pressure, and conversion rates; secondary outcomes encompassed operative metrics, anesthetic consumption, and 24-h VAS pain scores.Statistical analyses utilized longitudinal mixed models and t-tests.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e\u003cp\u003eThe estimation results showed that there is no statistically significant difference between the Low-Angle Group and the Steep-Angle Group in terms of HR, DBP, SBP and airway pressure at different time point during surgery. Airway pressures maintained strict proportionality to tidal volumes in both groups (12\u0026ndash;17 cmH\u003csub\u003e2\u003c/sub\u003eO, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.72).No significant differences were found between groups in conversion rates (4.0% vs. 4.3%, p\u0026thinsp;=\u0026thinsp;0.319), operative/anesthesia duration, blood loss, complications, or most recovery indicators. Anesthetic consumption and VAS scores for shoulder pain/PONV were also similar at 2h and 24h. The Low-Angle Group had significantly lower 24-h abdominal pain VAS (0.46\u0026thinsp;\u0026plusmn;\u0026thinsp;0.28 vs. 1.12\u0026thinsp;\u0026plusmn;\u0026thinsp;0.42, p\u0026thinsp;=\u0026thinsp;0.014), exceeding MCID thresholds.\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e\u003cp\u003ePerforming gasless vNOTES with \u0026le;\u0026thinsp;20\u0026deg; Trendelenburg achieves outcomes equivalent to \u0026ge;\u0026thinsp;30\u0026deg;, including surgical exposure and safety, while significantly reducing postoperative abdominal pain. This challenges the need for routine steep positioning, establishing\u0026thinsp;\u0026le;\u0026thinsp;20\u0026deg; as a viable patient-centered standard, offering equivalent efficacy with less discomfort. Further validation warranted.\u003c/p\u003e","manuscriptTitle":"Steep Trendelenburg Positioning in gasless vNOTES Procedures: A Retrospective Study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-12-04 00:12:50","doi":"10.21203/rs.3.rs-7813855/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-01-01T03:08:43+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-12-25T12:24:13+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-12-25T03:45:57+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-12-23T13:19:15+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"6114404430313533298134677374198924923","date":"2025-12-08T09:45:41+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"330963993742535931570982853311991889977","date":"2025-12-04T03:25:19+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"225464848626855821721230442373994171253","date":"2025-12-02T05:22:22+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-12-02T02:36:58+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-11-12T12:00:39+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-11-12T10:58:15+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-11-11T23:23:09+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Anesthesiology","date":"2025-11-11T23:20:08+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-anesthesiology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bane","sideBox":"Learn more about [BMC Anesthesiology](http://bmcanesthesiol.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/bane","title":"BMC Anesthesiology","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"c9e7ec24-2482-4690-8b0a-6538e0aa9d0e","owner":[],"postedDate":"December 4th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2026-04-13T16:08:27+00:00","versionOfRecord":{"articleIdentity":"rs-7813855","link":"https://doi.org/10.1186/s12871-026-03818-8","journal":{"identity":"bmc-anesthesiology","isVorOnly":false,"title":"BMC Anesthesiology"},"publishedOn":"2026-04-10 15:57:26","publishedOnDateReadable":"April 10th, 2026"},"versionCreatedAt":"2025-12-04 00:12:50","video":"","vorDoi":"10.1186/s12871-026-03818-8","vorDoiUrl":"https://doi.org/10.1186/s12871-026-03818-8","workflowStages":[]},"version":"v1","identity":"rs-7813855","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7813855","identity":"rs-7813855","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}