Effect of Trendelenburg position on post-induction hypotension in patients undergoing gastrointestinal surgery: A Randomized Clinical Trial

Effect of Trendelenburg position on post-induction hypotension in patients undergoing gastrointestinal surgery: A Randomized Clinical Trial | 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 Effect of Trendelenburg position on post-induction hypotension in patients undergoing gastrointestinal surgery: A Randomized Clinical Trial Ze Chai, Haojie Ying, Wen Zhang, Ping Chen, Shuang Fu, Shunv Cai, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8146302/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Background Hypotension during general anesthesia induction is common and linked to adverse outcomes. Positioning strategies such as the Trendelenburg position may help improve hemodynamics, but their effectiveness during induction remains unclear. Methods This single-center, prospective, randomized controlled trial was conducted at Zhejiang Cancer Hospital in China from June to August 2024. A total of 70 adult patients (ASA I–III) scheduled for laparoscopic colorectal or gastric cancer surgery were randomly assigned to either the Trendelenburg group (n = 35) or the supine group (n = 35). Immediately after loss of eyelash reflex, patients were positioned in a 10° Trendelenburg or supine position for 15 minutes. Standardized anesthesia, fluid therapy, and vasopressor protocols were applied. The primary outcome was the area under the curve (AUC) for mean arterial pressure (MAP) < 65 mmHg during the first 15 minutes post-induction. Secondary outcomes included AUC for MAP < 60 and < 50 mmHg, duration of hypotension, and drug usage. Statistical analyses involved appropriate non-parametric tests to compare the groups. Results The median AUC for MAP < 65 mmHg was 0 (0–0) mmHg·min in the Trendelenburg group versus 2.03 (0–5.40) mmHg·min in the supine group (P < 0.001). The duration of MAP < 65 mmHg was 0 minutes in the Trendelenburg group compared to 0.92 minutes in the supine group (P < 0.001). Vasopressor use and remifentanil doses were significantly lower in the Trendelenburg group. Conclusions Applying a 10° Trendelenburg position during anesthesia induction significantly reduces the incidence and severity of hypotension in patients undergoing gastrointestinal surgery. Larger multicenter studies are warranted to evaluate the impact on postoperative outcomes and recovery. Trial registration: The trial was registered on June 3, 2024, at http://www.chictr.org.cn/ , registration number ChiCTR2400085213. Hypotension Trendelenburg position Anesthesia induction Arterial pressure Gastrointestinal surgery Figures Figure 1 Figure 2 Figure 3 1. Introduction Hypotension is common in patients undergoing noncardiac surgery with general anesthesia, affecting approximately 80% of patients[ 1 ], and is associated with acute kidney injury[ 2 – 4 ], myocardial injury[ 5 ], and myocardial infarction[ 3 , 6 , 7 ]. About one-third of hypotensive episodes occur between induction of general anesthesia and surgical incision[ 8 ]. Several measures may be implemented to prevent hypotension during general anesthesia induction. Close monitoring, such as continuous arterial pressure monitoring, can effectively mitigate the incidence of hypotension[ 9 ]. However, the administration of vasopressor agents may still be required. Fluid resuscitation may cause harm to patients with poor cardiac function. Although the corrected carotid flow time measurement has proven useful in identifying true volume-depleted patients, it is a relatively complex procedure that requires a high level of skill from the operator, making it unsuitable for widespread application[ 10 ]. Adjusting the patient's position during surgery can influence hemodynamics. For example, the mean arterial blood pressure increased by 35% in the 45° Trendelenburg position in robot-assisted laparoscopic resection of rectal cancer[ 11 ]. However, the effectiveness of the Trendelenburg position in alleviating hypotension during general anesthesia induction compared to the supine position remains to be verified. Therefore, the present study explored the hypothesis that the Trendelenburg position after anesthesia induction can help shorten the duration for which the MAP remains < 65 mmHg in the initial 15 min after induction in patients undergoing gastrointestinal surgery. 2. Methods This prospective, single-blind, controlled study was conducted at Zhejiang Cancer Hospital between June 2024 and August 2024. The trial was approved by the Ethics Committee of Zhejiang Cancer Hospital (No. IRB-2024-366 on 16 April, 2024) and registered at chictr.org.cn (ChiCTR2400085213 on 3 June, 2024) in accordance with the Consolidated Standards of Reporting Trials (CONSORT) guidelines. All participants signed written consent prior to the study. 2.1. Subjects Patients aged 18 years or older with an American Society of Anesthesiologists physical status score of I–III scheduled for laparoscopic surgery for colorectal or gastric cancer were recruited. Exclusion criteria included individuals requiring emergency surgery, severe heart failure, intracranial aneurysms, severe preoperative hypertension or hypotension, pyloric or intestinal obstruction necessitating rapid sequential induction, predictable difficult airways, and severe liver and kidney dysfunction. Patients planning to receive epidural anesthesia in combination with general anesthesia were also excluded. 2.2. Randomization and blinding After informed consent was obtained, patients were randomly assigned to either a 10°Trendelenburg position or a supine position in a 1:1 ratio. Prior to the study’s commencement, a computer-generated randomization program was used to create a sequence for treatment allocation. This sequence was subsequently concealed in opaque, sequentially numbered envelopes by a research assistant who was not involved in the study. Only patients were blinded to group allocation, but anesthesiologists could not be. 2.3. Study protocol All patients were required to fast for at least 8 h and refrain from drinking for at least 2 h before surgery. The fasting period was extended for patients with delayed gastric emptying. In the operating room, all patients were equipped with standard anesthetic monitoring, including electrocardiogram, oxygen saturation and upper-arm cuff oscillometry. Then invasive arterial blood pressure was monitored after radial artery catheter was inserted. While the arterial transducer was placed at the intersection of the midaxillary line and the fifth intercostal space of the patient. A catheter is inserted into the right internal jugular vein for fluid administration. After the central line was established, crystalloid fluids were infused at a rate of 10 mL/kg/h. Additionally, subjects inhaled oxygen at a rate of 10 L/min for 2–3 min for preoxygenation prior to anesthesia induction. In both groups, general anesthesia was induced with Propofol (AstraZeneca, London, United Kingdom) and remifentanil (Yichang Humanwell, Hubei, China). Both propofol and remifentanil were administered via target-controlled infusion devices (TCI, B Braun, Melsungen, Germany). For induction, the propofol TCI was set to an initial effect-site target concentration of 3.5 µg/mL using the Marsh model, and the remifentanil TCI was set to an initial plasma target concentration of 4 ng/mL using the Minto model. Then rocuronium bromide (0.9 mg/kg) was given following loss of consciousness. Endotracheal intubation was performed when the effect-site propofol concentration reached 2 µg/mL. Subsequently, propofol and remifentanil concentrations were adjusted to 2.5 µg/mL and 2 ng/mL, respectively. Patients in the Trendelenburg position group were adjusted to a 10° Trendelenburg position following the disappearance of their eyelash reflex and maintained for 15 mins. Subsequently, subjects were gradually returned to a supine position. While patients in the supine position group remained in a supine position throughout. Apart from disinfection and urinary catheterization, surgeons were not permitted to perform any other procedures. Beat-to-beat arterial pressure values were meticulously recorded to monitor hemodynamic status during the first 15 min following the initial anesthetic injection. Continuous intra-arterial pressure monitoring was also implemented within the same timeframe to guarantee precise blood pressure data collection. Vasopressor drugs were used to maintain a MAP of ≥ 65 mmHg. If MAP was 40 beats/min, 40 µg of phenylephrine was administered. If there was no response after two doses, 0.5 mg of metaraminol was given. For MAP < 65 mmHg and HR < 40 beats/min, 5 mg of ephedrine was administered. For HR 180 mmHg or diastolic blood pressure (DBP) of > 110 mmHg, 12.5 mg of urapidil was administered. For MAP > 65 mmHg and HR > 110 beats/min, 30 mg of esmolol was given. 2.4. Invasive arterial blood pressure monitoring The continuously measured MAP from arterial catheters was used to quantify hypotension in all subjects. Beat-to-beat arterial pressure values were extracted. To correct for unequal numbers of beat-to-beat values due to intra-subject changes and inter-subject differences in heart rate, beat-to-beat MAP values were averaged in non-overlapping 5-s windows; these window means were used for primary and secondary endpoint analyses. Beat-to-beat arterial pressure artifacts were excluded using the following sequential rules: (1) arterial pressure values documented as artifacts by study personnel; (2) systolic arterial pressure > 280 or < 30 mmHg; (3) systolic arterial pressure below diastolic arterial pressure plus 5 mmHg; and (4) diastolic arterial pressure 150 mmHg. To calculate the hypotension area index, we first subtracted each 5-s mean MAP from the preset MAP threshold. Positive differences were used to calculate areas under the threshold. The differences were multiplied by 5 s and divided by 60 to obtain values in mmHg/min. All values were then summed over the 15-min observation period within each subject. 2.5. Endpoints Hypotension during anesthesia induction, defined quantitatively as the area under a MAP of 65 mmHg within the first 15 min post-induction (units: mmHg × min) served as the primary endpoint in the study. Secondary endpoints included: 1) area below MAP thresholds of 60 and 50 mmHg; and 2) duration for which MAP values remained < 65, < 60, and < 50 mmHg. We also assessed the total amounts of remifentanil, propofol, and crystalloids administered to the patients. 2.6. Statistical analysis The present study analyzed participants with recorded arterial pressure values during the entire 15-min trial period. Categorical data were presented as absolute numbers and percentages, whereas continuous data were reported as means with standard deviations, medians (25th to 75th percentiles), and ranges. To compare the demographic data between the two groups, the t -test and Fisher’s exact test were used to compare continuous and categorical variables, respectively. Primary and secondary endpoint indicators were analyzed using two-sample two-sided Wilcoxon rank-sum tests alongside continuity adjustments. P -values were calculated using the normal approximation method. Additionally, non-parametric 95% confidence interval (CI) and estimators for the differences of the location parameters were computed. The study results were considered significantly different when P < 0.01. 2.6. Sample size estimation Preliminary experiments have shown that the standard deviation of the AUC for MAP < 65 mmHg during the first 15 min of anesthesia induction of 2.98 mmHg·min. Therefore, we assumed a minimal detectable difference of 3.31 mmHg·min between groups, significant difference ( α ) = 0.01, and power of a test (1 – β ) = 0.95, while anticipating a 10% dropout rate. Using these parameters, the sample size computation within the Power Analysis and Sample Size (PASS) 2021 software determined to enroll 70 patients. 3. Results We randomized 90 patients but excluded 20 patients due to emergency surgery, declined to participate, diagnosed with severe heart failure, epidural anesthesia and rapid sequential induction. We thus included 70 patients with complete data recordings in the final analysis. 35 subjects were assigned to each of the Trendelenburg and supine position groups (Fig. 1 ). The baseline clinical characteristics were comparable between the two groups (Table 1 ). Table 1 Demographic, baseline, and clinical characteristics of the subjects (n = 70). Characteristic Trendelenburg position (n = 35) Supine position (n = 35) Age(yr) 62.5 ± 10.6 62.4 ± 8.8 Height(cm) 166.3 ± 9.6 165.1 ± 7.6 Weight(kg) 62.5 ± 11.1 64.4 ± 10.5 Body mass index(kg/m 2 ) 23.4 ± 3.5 23.4 ± 2.8 Sex(n) Male 21(60.0%) 25(71.4%) Female 14(40.0%) 10(28.6%) ASA physical status(n) 1 0 0 2 35(100.0%) 35(100.0%) 3 0 0 4 0 0 Baseline risk factors(n) Chronic hypertension 11(31.4%) 10(28.6%) Diabetes mellitus 4(11.4%) 6(17.1%) Chronic heart failure 1(2.9%) 1(2.9%) Radiotherapy 4(11.4%) 3(8.6%) Chemotherapy 5(14.3%) 11(31.4%) Surgical site(n) Rectum 17(48.6%) 20(57.1%) Left hemicolon 9(25.7%) 10(28.6%) Right hemicolon 9(25.7%) 5(14.3%) Clinical characteristics Lithotomy position during the induction phase(n) 18(51.4%) 35(100.0%) Time from induction start to loss of consciousness (s) 90(75–106) 86(68–107) Time from induction start to intubation(s) 267(247–277) 267(245–287) Categorical data are presented as number (n) and percentage, continuous data are mean ± SD or median (interquartile range). The median (25th to 75th percentile) AUC for MAP at 65 mmHg was 0 (0–0) mmHg·min in the Trendelenburg position group and 2.03 (0-5.40) mmHg·min ( P = 0.0003; estimated location shift: -13 [95% CI, -20 to -5] mmHg·min) in the supine position group (Table 2 , Fig. 2 ). The AUC for MAP at 60 mmHg was also significantly lower in the Trendelenburg position group compared to that in the supine position group (Table 2 , Fig. 2 ). Table 2 Summary of primary and secondary outcomes(n = 70). Outcome Trendelenburg position (n = 35) Supine position (n = 35) P-value AUC MAP < 65 mm Hg(mm Hg·min) 0.0003 Mean 0.74(2.65) 4.23(6.08) Median 0(0–0) 2.03(0-5.40) Range 0-14.6 0-23.73 AUC MAP < 60 mm Hg(mm Hg·min) 0.05 Mean 0.25(1.02) 2.21(4.61) Median 0(0–0) 0(0-2.11) Range 0-5.78 0-19.58 AUC MAP 0.99 Mean 0(0) 0.04(0.23) Median 0(0–0) 0(0–0) Range 0–0 0-1.33 Duration of MAP < 65 mm Hg(min) 0.0008 Mean 0.31(0.99) 1.33(1.52) Median 0(0–0) 0.92(0-1.88) Range 0-4.67 0-5.50 Duration of MAP < 60 mm Hg(min) 0.05 Mean 0.04(0.16) 0.27(0.51) Median 0(0–0) 0(0-0.33) Range 0-0.92 0–2 Remifentanil Total(µg) 113(105–123) 126(110–153) 0.01 Weight-adjusted dose(µg/kg) 1.85(1.62–1.95) 1.87(1.76–2.26) 0.42 Propofol Total(mg) 173(161–206) 187(168–228) 0.14 Weight-adjusted dose(mg/kg) 2.86(2.84–2.90) 2.92(2.87–3.10) 0.004 Crystalloid(ml) 157(140–180) 170(153–200) 0.07 Any vasopressor use(n) 4(11.4%) 22(62.9%) Phenylephrine(µg) 0(0–0) 40(0–80) 0.0002 Metaraminol(mg) 0(0–0) 0(0–0) 0.32 Ephedrine(mg) 0(0–0) 0(0–0) 0.16 Data are presented as mean (SD), median (interquartile range), and range, or absolute number (percentage). P values correspond to Wilcoxon rank-sum tests with continuity correction. AUC, area under the curve; n, absolute number. Amounts of remifentanil, propofol, and crystalloid (total and per kg), and doses of phenylephrine (µg), metaraminol (mg), and ephedrine (mg) refer to use in the first 15 minutes after anesthetic induction. The median (25th to 75th percentile) duration of MAP < 65 mmHg was 0 (0–0) min in the Trendelenburg position group compared to 0.92 (0-1.88) min in the supine position group ( P = 0.0008; Table 2 , Fig. 3 ). Furthermore, the duration of MAP < 60 mmHg was also significantly shorter in the Trendelenburg position group than that in the supine position group (Table 2 , Fig. 3 ). During the first 15 minutes following anesthesia induction, the weight-adjusted dose of remifentanil was 1.85 (1.62–1.95) µg/kg in the Trendelenburg position group and 1.87 (1.76–2.26) µg/kg in the supine position group (P = 0.42; Table 2 ). The total dose of propofol administered was 173 (161–206) mg in the Trendelenburg position group and 187 (168–228) mg in the supine position group (P = 0.14; Table 2 ). The volume of crystalloid infused was 157 (140–180) ml in the Trendelenburg position group compared to 170 (153–200) ml in the supine position group (P = 0.07; Table 2 ). The phenylephrine dose was 0 (0–0) µg in the Trendelenburg position group and 40 (0–80) µg in the supine position group (P = 0.0002; Table 2 ). 4. Discussion This randomized controlled trial demonstrated that patients in a 10° Trendelenburg position during induction of general anesthesia for gastrointestinal surgery significantly reduced both the severity and duration of hypotension compared with the supine position. Perioperative hypotension is a frequently encountered phenomenon in anesthesia management and a significant factor contributing to inadequate organ perfusion during surgery. Prolonged episodes of hypotension can result in multi-organ dysfunction, with critical effects on vital organs such as the heart, brain, and kidneys[ 12 – 14 ]. Moreover, hypotension has been linked to cerebral hypoperfusion, which may exacerbate the incidence of postoperative cognitive dysfunction (POCD), particularly in elderly patients[ 15 – 17 ]. Observational studies have also suggested that perioperative hypotension may increase the risk of postoperative delirium or cognitive dysfunction[ 18 – 20 ], highlighting the importance of effective intraoperative hemodynamic management to mitigate these risks. In this study, the duration of MAP < 65 mmHg during induction of general anesthesia was shorter than that in previous studies[ 9 ], which may be attributable to several factors. First, propofol and remifentanil administered via TCI mode has a lighter impact on the patient's hemodynamics compared to the bolus administration method[ 21 ]. Second, from tracheal intubation to skin incision, propofol was adjusted to 2.5 µg/mL and remifentanil to 2 ng/mL, which were lower than the initial target concentrations set during anesthesia induction and thus had a smaller impact on the patient's blood pressure. To explore the underlying mechanism, we believe that the Trendelenburg position can increase central blood volume by promoting venous blood return from the lower limbs to the heart and redistributing more blood to the thoracic and cranial regions, which helps maintain and elevate blood pressure[ 22 ]. For clinicians, this indicates that a short-duration, low-angle Trendelenburg position can be a valuable non-pharmacological adjunct in hemodynamic management during anesthesia induction, particularly in elderly patients. This approach may potentially reduce the need for vasopressors. A gradual positioning adjustment strategy can be employed when implementing this method, including the gradual lowering of the head position instead of sudden changes, to allow the body sufficient time to acclimate to the new blood flow distribution. Nevertheless, caution should be exercised in relation to patients with full stomachs to prevent an elevated risk of reflux with a lowered head position[ 23 ]. Nonetheless, the study has several limitations. First, it was a single-center investigation with a small sample size, which makes it impossible to determine whether the observed reduction in hypotension during anesthesia induction translates into a decrease in postoperative complications. Second, patients who were scheduled for laparoscopic gastric surgery were not included in the final study cohort due to the lack of monitoring equipment capable of collecting data per second in the operating room of gastric surgery. Third, only patients were blinded to group allocation; anesthesiologists could not be blinded, which may have introduced performance bias. Finally, this study included all adult patients. However, elderly patients are more prone to hypotension during induction, and further research is needed to explore the effects of the Trendelenburg position in this population. Conclusions The Trendelenburg position significantly reduced the incidence of post-induction hypotension in patients undergoing gastrointestinal surgery compared to the supine position. This study provides new option for clinical practice, especially in those who are prone to hypotension during the induction period. Abbreviations AUC MAP TCI HR SBP DBP CI PASS POCD Area under the curve Mean arterial pressure Target-controlled infusion Heart rate Systolic blood pressure Diastolic blood pressure Confidence interval Power Analysis and Sample Size Postoperative cognitive dysfunction Declarations Human Ethics and Consent to Participate : This study was performed following the guidelines of the Declaration of Helsinki (2013). Ethical approval was obtained from the Medical Ethics Committee of Zhejiang Cancer Hospital (Date: April 16, 2024; Approval number: IRB-2024-366(IIT)). Additionally, institutional permission was secured. Informed written consent was obtained from the study participants, and privacy was maintained throughout data collection. Whether the patients participated in the study or not did not affect the treatment and care they received. Consent for publication: Not applicable. Competing interests: The authors declare that they have no competing interests. Funding: This work was supported by Zhejiang Medical Health Science and Technology Project (Grant number 2024KY039, 2024KY827 and 2021ZH020) and 2024ZZBS13 of Hangzhou Institute of Medicine, Chinese Academy of Sciences. Author Contribution ZC and HJY contributed substantially to the design and conduct of the study, data collection, and wrote the first draft of the manuscript. PC and WZ contributed to the recruitment of the patients and data collection. SF contributed to statistical analysis. SNC, GB and PBX contributed to the study design and provided revision to the manuscript. All authors read and approved the final manuscript. Acknowledgement The authors thank the staff of the Department of Anesthesiology and the Department of Colorectal Surgery at Zhejiang Cancer Hospital for their help and cooperation in this study. Data Availability The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request. 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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-8146302","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":556599727,"identity":"a312a989-8877-4e55-8196-dbabb5103b25","order_by":0,"name":"Ze Chai","email":"","orcid":"","institution":"Zhejiang Cancer Hospital","correspondingAuthor":false,"prefix":"","firstName":"Ze","middleName":"","lastName":"Chai","suffix":""},{"id":556599728,"identity":"de1d3077-797b-4d20-859c-066a91fac21e","order_by":1,"name":"Haojie Ying","email":"","orcid":"","institution":"Zhejiang Chinese Medical 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1","display":"","copyAsset":false,"role":"figure","size":60649,"visible":true,"origin":"","legend":"\u003cp\u003eFlow chart illustrating patient screening, enrollment, randomization, and reasons for exclusion.\u003c/p\u003e","description":"","filename":"Fig1.png","url":"https://assets-eu.researchsquare.com/files/rs-8146302/v1/e81c0812e14c718c34549e24.png"},{"id":97706023,"identity":"aed5e332-8a40-41c5-abb3-21649e24e71a","added_by":"auto","created_at":"2025-12-08 12:54:33","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":2350372,"visible":true,"origin":"","legend":"\u003cp\u003eBoxplots with overlaying scatter plots illustrating areas under MAP values of 65, 60, and 50 mm Hg in subjects assigned to Trendelenburg position group and Supine position group.\u003c/p\u003e","description":"","filename":"Fig2.png","url":"https://assets-eu.researchsquare.com/files/rs-8146302/v1/f84b67501cdabb5aa949ac10.png"},{"id":97706010,"identity":"0238e81e-cf22-4856-ac3c-75f781004d30","added_by":"auto","created_at":"2025-12-08 12:54:31","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":2324239,"visible":true,"origin":"","legend":"\u003cp\u003eBoxplots with overlaying scatter plots illustrating durations under MAP values of 65, 60, and 50 mmHg in subjects assigned to Trendelenburg position group and Supine position group.\u003c/p\u003e","description":"","filename":"Fig3.png","url":"https://assets-eu.researchsquare.com/files/rs-8146302/v1/5e9ff38c94c3dea418da60a3.png"},{"id":101297199,"identity":"0b392309-74a5-4b68-9a93-79ecd6887d54","added_by":"auto","created_at":"2026-01-28 09:25:52","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":852771,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8146302/v1/51935258-9c04-4a8e-873f-0faf3e9b9ff8.pdf"},{"id":97705942,"identity":"407f4e86-8ff2-4ec9-88ad-d777028a57e5","added_by":"auto","created_at":"2025-12-08 12:54:23","extension":"doc","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":223232,"visible":true,"origin":"","legend":"","description":"","filename":"CONSORT2010ChecklistMSWord.doc","url":"https://assets-eu.researchsquare.com/files/rs-8146302/v1/2ee3f967b2106060fa071d01.doc"}],"financialInterests":"No competing interests reported.","formattedTitle":"Effect of Trendelenburg position on post-induction hypotension in patients undergoing gastrointestinal surgery: A Randomized Clinical Trial","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eHypotension is common in patients undergoing noncardiac surgery with general anesthesia, affecting approximately 80% of patients[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e], and is associated with acute kidney injury[\u003cspan additionalcitationids=\"CR3\" citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e], myocardial injury[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e], and myocardial infarction[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. About one-third of hypotensive episodes occur between induction of general anesthesia and surgical incision[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eSeveral measures may be implemented to prevent hypotension during general anesthesia induction. Close monitoring, such as continuous arterial pressure monitoring, can effectively mitigate the incidence of hypotension[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. However, the administration of vasopressor agents may still be required. Fluid resuscitation may cause harm to patients with poor cardiac function. Although the corrected carotid flow time measurement has proven useful in identifying true volume-depleted patients, it is a relatively complex procedure that requires a high level of skill from the operator, making it unsuitable for widespread application[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eAdjusting the patient's position during surgery can influence hemodynamics. For example, the mean arterial blood pressure increased by 35% in the 45\u0026deg; Trendelenburg position in robot-assisted laparoscopic resection of rectal cancer[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. However, the effectiveness of the Trendelenburg position in alleviating hypotension during general anesthesia induction compared to the supine position remains to be verified. Therefore, the present study explored the hypothesis that the Trendelenburg position after anesthesia induction can help shorten the duration for which the MAP remains\u0026thinsp;\u0026lt;\u0026thinsp;65 mmHg in the initial 15 min after induction in patients undergoing gastrointestinal surgery.\u003c/p\u003e"},{"header":"2. Methods","content":"\u003cp\u003eThis prospective, single-blind, controlled study was conducted at Zhejiang Cancer Hospital between June 2024 and August 2024. The trial was approved by the Ethics Committee of Zhejiang Cancer Hospital (No. IRB-2024-366 on 16 April, 2024) and registered at chictr.org.cn (ChiCTR2400085213 on 3 June, 2024) in accordance with the Consolidated Standards of Reporting Trials (CONSORT) guidelines. All participants signed written consent prior to the study.\u003c/p\u003e\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1. Subjects\u003c/h2\u003e\u003cp\u003ePatients aged 18 years or older with an American Society of Anesthesiologists physical status score of I\u0026ndash;III scheduled for laparoscopic surgery for colorectal or gastric cancer were recruited. Exclusion criteria included individuals requiring emergency surgery, severe heart failure, intracranial aneurysms, severe preoperative hypertension or hypotension, pyloric or intestinal obstruction necessitating rapid sequential induction, predictable difficult airways, and severe liver and kidney dysfunction. Patients planning to receive epidural anesthesia in combination with general anesthesia were also excluded.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2. Randomization and blinding\u003c/h2\u003e\u003cp\u003eAfter informed consent was obtained, patients were randomly assigned to either a 10\u0026deg;Trendelenburg position or a supine position in a 1:1 ratio. Prior to the study\u0026rsquo;s commencement, a computer-generated randomization program was used to create a sequence for treatment allocation. This sequence was subsequently concealed in opaque, sequentially numbered envelopes by a research assistant who was not involved in the study. Only patients were blinded to group allocation, but anesthesiologists could not be.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3. Study protocol\u003c/h2\u003e\u003cp\u003eAll patients were required to fast for at least 8 h and refrain from drinking for at least 2 h before surgery. The fasting period was extended for patients with delayed gastric emptying. In the operating room, all patients were equipped with standard anesthetic monitoring, including electrocardiogram, oxygen saturation and upper-arm cuff oscillometry. Then invasive arterial blood pressure was monitored after radial artery catheter was inserted. While the arterial transducer was placed at the intersection of the midaxillary line and the fifth intercostal space of the patient. A catheter is inserted into the right internal jugular vein for fluid administration. After the central line was established, crystalloid fluids were infused at a rate of 10 mL/kg/h. Additionally, subjects inhaled oxygen at a rate of 10 L/min for 2\u0026ndash;3 min for preoxygenation prior to anesthesia induction.\u003c/p\u003e\u003cp\u003eIn both groups, general anesthesia was induced with Propofol (AstraZeneca, London, United Kingdom) and remifentanil (Yichang Humanwell, Hubei, China). Both propofol and remifentanil were administered via target-controlled infusion devices (TCI, B Braun, Melsungen, Germany). For induction, the propofol TCI was set to an initial effect-site target concentration of 3.5 \u0026micro;g/mL using the Marsh model, and the remifentanil TCI was set to an initial plasma target concentration of 4 ng/mL using the Minto model. Then rocuronium bromide (0.9 mg/kg) was given following loss of consciousness. Endotracheal intubation was performed when the effect-site propofol concentration reached 2 \u0026micro;g/mL. Subsequently, propofol and remifentanil concentrations were adjusted to 2.5 \u0026micro;g/mL and 2 ng/mL, respectively.\u003c/p\u003e\u003cp\u003ePatients in the Trendelenburg position group were adjusted to a 10\u0026deg; Trendelenburg position following the disappearance of their eyelash reflex and maintained for 15 mins. Subsequently, subjects were gradually returned to a supine position. While patients in the supine position group remained in a supine position throughout. Apart from disinfection and urinary catheterization, surgeons were not permitted to perform any other procedures.\u003c/p\u003e\u003cp\u003eBeat-to-beat arterial pressure values were meticulously recorded to monitor hemodynamic status during the first 15 min following the initial anesthetic injection. Continuous intra-arterial pressure monitoring was also implemented within the same timeframe to guarantee precise blood pressure data collection.\u003c/p\u003e\u003cp\u003eVasopressor drugs were used to maintain a MAP of \u0026ge;\u0026thinsp;65 mmHg. If MAP was \u0026lt;\u0026thinsp;65 mmHg and heart rate (HR) was \u0026gt;\u0026thinsp;40 beats/min, 40 \u0026micro;g of phenylephrine was administered. If there was no response after two doses, 0.5 mg of metaraminol was given. For MAP\u0026thinsp;\u0026lt;\u0026thinsp;65 mmHg and HR\u0026thinsp;\u0026lt;\u0026thinsp;40 beats/min, 5 mg of ephedrine was administered. For HR\u0026thinsp;\u0026lt;\u0026thinsp;40 beats/min and MAP\u0026thinsp;\u0026ge;\u0026thinsp;65mmHg, 0.5 mg of atropine was administered. For systolic blood pressure (SBP) of \u0026gt;\u0026thinsp;180 mmHg or diastolic blood pressure (DBP) of \u0026gt;\u0026thinsp;110 mmHg, 12.5 mg of urapidil was administered. For MAP\u0026thinsp;\u0026gt;\u0026thinsp;65 mmHg and HR\u0026thinsp;\u0026gt;\u0026thinsp;110 beats/min, 30 mg of esmolol was given.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003e2.4. Invasive arterial blood pressure monitoring\u003c/h2\u003e\u003cp\u003eThe continuously measured MAP from arterial catheters was used to quantify hypotension in all subjects. Beat-to-beat arterial pressure values were extracted. To correct for unequal numbers of beat-to-beat values due to intra-subject changes and inter-subject differences in heart rate, beat-to-beat MAP values were averaged in non-overlapping 5-s windows; these window means were used for primary and secondary endpoint analyses.\u003c/p\u003e\u003cp\u003eBeat-to-beat arterial pressure artifacts were excluded using the following sequential rules: (1) arterial pressure values documented as artifacts by study personnel; (2) systolic arterial pressure\u0026thinsp;\u0026gt;\u0026thinsp;280 or \u0026lt;\u0026thinsp;30 mmHg; (3) systolic arterial pressure below diastolic arterial pressure plus 5 mmHg; and (4) diastolic arterial pressure\u0026thinsp;\u0026lt;\u0026thinsp;10 or \u0026gt;\u0026thinsp;150 mmHg.\u003c/p\u003e\u003cp\u003eTo calculate the hypotension area index, we first subtracted each 5-s mean MAP from the preset MAP threshold. Positive differences were used to calculate areas under the threshold. The differences were multiplied by 5 s and divided by 60 to obtain values in mmHg/min. All values were then summed over the 15-min observation period within each subject.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\u003ch2\u003e2.5. Endpoints\u003c/h2\u003e\u003cp\u003eHypotension during anesthesia induction, defined quantitatively as the area under a MAP of 65 mmHg within the first 15 min post-induction (units: mmHg \u0026times; min) served as the primary endpoint in the study. Secondary endpoints included: 1) area below MAP thresholds of 60 and 50 mmHg; and 2) duration for which MAP values remained\u0026thinsp;\u0026lt;\u0026thinsp;65, \u0026lt;\u0026thinsp;60, and \u0026lt;\u0026thinsp;50 mmHg. We also assessed the total amounts of remifentanil, propofol, and crystalloids administered to the patients.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003e2.6. Statistical analysis\u003c/h2\u003e\u003cp\u003eThe present study analyzed participants with recorded arterial pressure values during the entire 15-min trial period. Categorical data were presented as absolute numbers and percentages, whereas continuous data were reported as means with standard deviations, medians (25th to 75th percentiles), and ranges. To compare the demographic data between the two groups, the \u003cem\u003et\u003c/em\u003e-test and Fisher\u0026rsquo;s exact test were used to compare continuous and categorical variables, respectively.\u003c/p\u003e\u003cp\u003ePrimary and secondary endpoint indicators were analyzed using two-sample two-sided Wilcoxon rank-sum tests alongside continuity adjustments. \u003cem\u003eP\u003c/em\u003e-values were calculated using the normal approximation method. Additionally, non-parametric 95% confidence interval (CI) and estimators for the differences of the location parameters were computed. The study results were considered significantly different when \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\u003ch2\u003e2.6. Sample size estimation\u003c/h2\u003e\u003cp\u003ePreliminary experiments have shown that the standard deviation of the AUC for MAP\u0026thinsp;\u0026lt;\u0026thinsp;65 mmHg during the first 15 min of anesthesia induction of 2.98 mmHg\u0026middot;min. Therefore, we assumed a minimal detectable difference of 3.31 mmHg\u0026middot;min between groups, significant difference (\u003cem\u003eα\u003c/em\u003e)\u0026thinsp;=\u0026thinsp;0.01, and power of a test (1 \u0026ndash; \u003cem\u003eβ\u003c/em\u003e)\u0026thinsp;=\u0026thinsp;0.95, while anticipating a 10% dropout rate. Using these parameters, the sample size computation within the Power Analysis and Sample Size (PASS) 2021 software determined to enroll 70 patients.\u003c/p\u003e\u003c/div\u003e"},{"header":"3. Results","content":"\u003cp\u003eWe randomized 90 patients but excluded 20 patients due to emergency surgery, declined to participate, diagnosed with severe heart failure, epidural anesthesia and rapid sequential induction. We thus included 70 patients with complete data recordings in the final analysis. 35 subjects were assigned to each of the Trendelenburg and supine position groups (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The baseline clinical characteristics were comparable between the two groups (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eDemographic, baseline, and clinical characteristics of the subjects (n\u0026thinsp;=\u0026thinsp;70).\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"3\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCharacteristic\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTrendelenburg position\u003c/p\u003e\u003cp\u003e(n\u0026thinsp;=\u0026thinsp;35)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eSupine position\u003c/p\u003e\u003cp\u003e(n\u0026thinsp;=\u0026thinsp;35)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAge(yr)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e62.5\u0026thinsp;\u0026plusmn;\u0026thinsp;10.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e62.4\u0026thinsp;\u0026plusmn;\u0026thinsp;8.8\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHeight(cm)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e166.3\u0026thinsp;\u0026plusmn;\u0026thinsp;9.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e165.1\u0026thinsp;\u0026plusmn;\u0026thinsp;7.6\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eWeight(kg)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e62.5\u0026thinsp;\u0026plusmn;\u0026thinsp;11.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e64.4\u0026thinsp;\u0026plusmn;\u0026thinsp;10.5\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBody mass index(kg/m\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e23.4\u0026thinsp;\u0026plusmn;\u0026thinsp;3.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e23.4\u0026thinsp;\u0026plusmn;\u0026thinsp;2.8\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSex(n)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMale\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e21(60.0%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e25(71.4%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eFemale\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e14(40.0%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e10(28.6%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eASA physical status(n)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e35(100.0%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e35(100.0%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBaseline risk factors(n)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eChronic hypertension\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e11(31.4%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e10(28.6%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDiabetes mellitus\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e4(11.4%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e6(17.1%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eChronic heart failure\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1(2.9%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1(2.9%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRadiotherapy\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e4(11.4%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e3(8.6%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eChemotherapy\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e5(14.3%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e11(31.4%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSurgical site(n)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRectum\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e17(48.6%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e20(57.1%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLeft hemicolon\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e9(25.7%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e10(28.6%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRight hemicolon\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e9(25.7%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e5(14.3%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eClinical characteristics\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLithotomy position during the induction phase(n)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e18(51.4%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e35(100.0%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTime from induction start to loss of consciousness (s)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e90(75\u0026ndash;106)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e86(68\u0026ndash;107)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTime from induction start to intubation(s)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e267(247\u0026ndash;277)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e267(245\u0026ndash;287)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"3\"\u003eCategorical data are presented as number (n) and percentage, continuous data are mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD or median (interquartile range).\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eThe median (25th to 75th percentile) AUC for MAP at 65 mmHg was 0 (0\u0026ndash;0) mmHg\u0026middot;min in the Trendelenburg position group and 2.03 (0-5.40) mmHg\u0026middot;min (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.0003; estimated location shift: -13 [95% CI, -20 to -5] mmHg\u0026middot;min) in the supine position group (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The AUC for MAP at 60 mmHg was also significantly lower in the Trendelenburg position group compared to that in the supine position group (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eSummary of primary and secondary outcomes(n\u0026thinsp;=\u0026thinsp;70).\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eOutcome\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTrendelenburg position\u003c/p\u003e\u003cp\u003e(n\u0026thinsp;=\u0026thinsp;35)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eSupine position\u003c/p\u003e\u003cp\u003e(n\u0026thinsp;=\u0026thinsp;35)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP-value\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e\u003cp\u003eAUC MAP\u0026thinsp;\u0026lt;\u0026thinsp;65 mm Hg(mm Hg\u0026middot;min)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.0003\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMean\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.74(2.65)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4.23(6.08)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMedian\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0(0\u0026ndash;0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2.03(0-5.40)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRange\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0-14.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0-23.73\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e\u003cp\u003eAUC MAP\u0026thinsp;\u0026lt;\u0026thinsp;60 mm Hg(mm Hg\u0026middot;min)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.05\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMean\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.25(1.02)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2.21(4.61)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMedian\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0(0\u0026ndash;0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0(0-2.11)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRange\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0-5.78\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0-19.58\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e\u003cp\u003eAUC MAP\u0026thinsp;\u0026lt;\u0026thinsp;50 mm Hg(mm Hg\u0026middot;min)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026gt;0.99\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMean\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0(0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.04(0.23)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMedian\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0(0\u0026ndash;0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0(0\u0026ndash;0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRange\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0\u0026ndash;0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0-1.33\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e\u003cp\u003eDuration of MAP\u0026thinsp;\u0026lt;\u0026thinsp;65 mm Hg(min)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.0008\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMean\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.31(0.99)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1.33(1.52)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMedian\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0(0\u0026ndash;0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.92(0-1.88)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRange\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0-4.67\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0-5.50\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e\u003cp\u003eDuration of MAP\u0026thinsp;\u0026lt;\u0026thinsp;60 mm Hg(min)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.05\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMean\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.04(0.16)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.27(0.51)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMedian\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0(0\u0026ndash;0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0(0-0.33)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRange\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0-0.92\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0\u0026ndash;2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e\u003cp\u003eRemifentanil\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTotal(\u0026micro;g)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e113(105\u0026ndash;123)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e126(110\u0026ndash;153)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.01\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eWeight-adjusted dose(\u0026micro;g/kg)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1.85(1.62\u0026ndash;1.95)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1.87(1.76\u0026ndash;2.26)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.42\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e\u003cp\u003ePropofol\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTotal(mg)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e173(161\u0026ndash;206)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e187(168\u0026ndash;228)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.14\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eWeight-adjusted dose(mg/kg)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e2.86(2.84\u0026ndash;2.90)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2.92(2.87\u0026ndash;3.10)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.004\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCrystalloid(ml)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e157(140\u0026ndash;180)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e170(153\u0026ndash;200)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.07\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAny vasopressor use(n)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e4(11.4%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e22(62.9%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePhenylephrine(\u0026micro;g)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0(0\u0026ndash;0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e40(0\u0026ndash;80)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.0002\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMetaraminol(mg)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0(0\u0026ndash;0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0(0\u0026ndash;0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.32\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eEphedrine(mg)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0(0\u0026ndash;0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0(0\u0026ndash;0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.16\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"4\"\u003eData are presented as mean (SD), median (interquartile range), and range, or absolute number (percentage). P values correspond to Wilcoxon rank-sum tests with continuity correction. AUC, area under the curve; n, absolute number. Amounts of remifentanil, propofol, and crystalloid (total and per kg), and doses of phenylephrine (\u0026micro;g), metaraminol (mg), and ephedrine (mg) refer to use in the first 15 minutes after anesthetic induction.\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe median (25th to 75th percentile) duration of MAP\u0026thinsp;\u0026lt;\u0026thinsp;65 mmHg was 0 (0\u0026ndash;0) min in the Trendelenburg position group compared to 0.92 (0-1.88) min in the supine position group (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.0008; Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). Furthermore, the duration of MAP\u0026thinsp;\u0026lt;\u0026thinsp;60 mmHg was also significantly shorter in the Trendelenburg position group than that in the supine position group (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eDuring the first 15 minutes following anesthesia induction, the weight-adjusted dose of remifentanil was 1.85 (1.62\u0026ndash;1.95) \u0026micro;g/kg in the Trendelenburg position group and 1.87 (1.76\u0026ndash;2.26) \u0026micro;g/kg in the supine position group (P\u0026thinsp;=\u0026thinsp;0.42; Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The total dose of propofol administered was 173 (161\u0026ndash;206) mg in the Trendelenburg position group and 187 (168\u0026ndash;228) mg in the supine position group (P\u0026thinsp;=\u0026thinsp;0.14; Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The volume of crystalloid infused was 157 (140\u0026ndash;180) ml in the Trendelenburg position group compared to 170 (153\u0026ndash;200) ml in the supine position group (P\u0026thinsp;=\u0026thinsp;0.07; Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The phenylephrine dose was 0 (0\u0026ndash;0) \u0026micro;g in the Trendelenburg position group and 40 (0\u0026ndash;80) \u0026micro;g in the supine position group (P\u0026thinsp;=\u0026thinsp;0.0002; Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e"},{"header":"4. Discussion","content":"\u003cp\u003eThis randomized controlled trial demonstrated that patients in a 10\u0026deg; Trendelenburg position during induction of general anesthesia for gastrointestinal surgery significantly reduced both the severity and duration of hypotension compared with the supine position.\u003c/p\u003e\u003cp\u003ePerioperative hypotension is a frequently encountered phenomenon in anesthesia management and a significant factor contributing to inadequate organ perfusion during surgery. Prolonged episodes of hypotension can result in multi-organ dysfunction, with critical effects on vital organs such as the heart, brain, and kidneys[\u003cspan additionalcitationids=\"CR13\" citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. Moreover, hypotension has been linked to cerebral hypoperfusion, which may exacerbate the incidence of postoperative cognitive dysfunction (POCD), particularly in elderly patients[\u003cspan additionalcitationids=\"CR16\" citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. Observational studies have also suggested that perioperative hypotension may increase the risk of postoperative delirium or cognitive dysfunction[\u003cspan additionalcitationids=\"CR19\" citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e], highlighting the importance of effective intraoperative hemodynamic management to mitigate these risks.\u003c/p\u003e\u003cp\u003eIn this study, the duration of MAP\u0026thinsp;\u0026lt;\u0026thinsp;65 mmHg during induction of general anesthesia was shorter than that in previous studies[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e], which may be attributable to several factors. First, propofol and remifentanil administered via TCI mode has a lighter impact on the patient's hemodynamics compared to the bolus administration method[\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Second, from tracheal intubation to skin incision, propofol was adjusted to 2.5 \u0026micro;g/mL and remifentanil to 2 ng/mL, which were lower than the initial target concentrations set during anesthesia induction and thus had a smaller impact on the patient's blood pressure.\u003c/p\u003e\u003cp\u003eTo explore the underlying mechanism, we believe that the Trendelenburg position can increase central blood volume by promoting venous blood return from the lower limbs to the heart and redistributing more blood to the thoracic and cranial regions, which helps maintain and elevate blood pressure[\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eFor clinicians, this indicates that a short-duration, low-angle Trendelenburg position can be a valuable non-pharmacological adjunct in hemodynamic management during anesthesia induction, particularly in elderly patients. This approach may potentially reduce the need for vasopressors. A gradual positioning adjustment strategy can be employed when implementing this method, including the gradual lowering of the head position instead of sudden changes, to allow the body sufficient time to acclimate to the new blood flow distribution. Nevertheless, caution should be exercised in relation to patients with full stomachs to prevent an elevated risk of reflux with a lowered head position[\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eNonetheless, the study has several limitations. First, it was a single-center investigation with a small sample size, which makes it impossible to determine whether the observed reduction in hypotension during anesthesia induction translates into a decrease in postoperative complications. Second, patients who were scheduled for laparoscopic gastric surgery were not included in the final study cohort due to the lack of monitoring equipment capable of collecting data per second in the operating room of gastric surgery. Third, only patients were blinded to group allocation; anesthesiologists could not be blinded, which may have introduced performance bias. Finally, this study included all adult patients. However, elderly patients are more prone to hypotension during induction, and further research is needed to explore the effects of the Trendelenburg position in this population.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eThe Trendelenburg position significantly reduced the incidence of post-induction hypotension in patients undergoing gastrointestinal surgery compared to the supine position. This study provides new option for clinical practice, especially in those who are prone to hypotension during the induction period.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" class=\"fr-table-selection-hover\" style=\"margin-right: calc(18%); width: 82%;\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 25%;\"\u003e\n \u003cp\u003eAUC\u003c/p\u003e\n \u003cp\u003eMAP\u003c/p\u003e\n \u003cp\u003eTCI\u003c/p\u003e\n \u003cp\u003eHR\u003c/p\u003e\n \u003cp\u003eSBP\u003c/p\u003e\n \u003cp\u003eDBP\u003c/p\u003e\n \u003cp\u003eCI\u003c/p\u003e\n \u003cp\u003ePASS\u003c/p\u003e\n \u003cp\u003ePOCD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 75%;\"\u003e\n \u003cp\u003eArea under the curve\u003c/p\u003e\n \u003cp\u003eMean arterial pressure\u003c/p\u003e\n \u003cp\u003eTarget-controlled infusion\u003c/p\u003e\n \u003cp\u003eHeart rate\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eSystolic blood pressure\u003c/p\u003e\n \u003cp\u003eDiastolic blood pressure\u003c/p\u003e\n \u003cp\u003eConfidence interval\u003c/p\u003e\n \u003cp\u003ePower Analysis and Sample Size\u003c/p\u003e\n \u003cp\u003ePostoperative cognitive dysfunction\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cb\u003eHuman Ethics and Consent to Participate\u003c/b\u003e: This study was performed following the guidelines of the Declaration of Helsinki (2013). Ethical approval was obtained from the Medical Ethics Committee of Zhejiang Cancer Hospital (Date: April 16, 2024; Approval number: IRB-2024-366(IIT)). Additionally, institutional permission was secured. Informed written consent was obtained from the study participants, and privacy was maintained throughout data collection. Whether the patients participated in the study or not did not affect the treatment and care they received.\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eConsent for publication:\u003c/strong\u003e\u003cp\u003eNot applicable.\u003c/p\u003e\u003ch2\u003eCompeting interests:\u003c/h2\u003e\u003cp\u003eThe authors declare that they have no competing interests.\u003c/p\u003e\u003ch2\u003eFunding:\u003c/h2\u003e\u003cp\u003eThis work was supported by Zhejiang Medical Health Science and Technology Project (Grant number 2024KY039, 2024KY827 and 2021ZH020) and 2024ZZBS13 of Hangzhou Institute of Medicine, Chinese Academy of Sciences.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eZC and HJY contributed substantially to the design and conduct of the study, data collection, and wrote the first draft of the manuscript. PC and WZ contributed to the recruitment of the patients and data collection. SF contributed to statistical analysis. SNC, GB and PBX contributed to the study design and provided revision to the manuscript. All authors read and approved the final manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eThe authors thank the staff of the Department of Anesthesiology and the Department of Colorectal Surgery at Zhejiang Cancer Hospital for their help and cooperation in this study.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eNakanishi T, Tsuji T, Sento Y, Hashimoto H, Fujiwara K, Sobue K. Association between postinduction hypotension and postoperative mortality: a single-centre retrospective cohort study. Canadian Journal of Anaesthesia; 2023.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eShaw AD, Khanna AK, Smischney NJ, et al. Intraoperative hypotension is associated with persistent acute kidney disease after noncardiac surgery: a multicentre cohort study. Br J Anaesth. 2022;129(1):13\u0026ndash;21.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eGregory A, Stapelfeldt WH, Khanna AK, et al. Intraoperative Hypotension Is Associated With Adverse Clinical Outcomes After Noncardiac Surgery. Anesth Analg. 2021;132(6):1654\u0026ndash;65.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMathis MR, Naik BI, Freundlich RE, et al. Preoperative Risk and the Association between Hypotension and Postoperative Acute Kidney Injury. Anesthesiology. 2020;132(3):461\u0026ndash;75.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAhuja S, Mascha EJ, Yang D, et al. Associations of Intraoperative Radial Arterial Systolic, Diastolic, Mean, and Pulse Pressures with Myocardial and Acute Kidney Injury after Noncardiac Surgery: A Retrospective Cohort Analysis. Anesthesiology. 2020;132(2):291\u0026ndash;306.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eRoshanov PS, Sheth T, Duceppe E, et al. Relationship between Perioperative Hypotension and Perioperative Cardiovascular Events in Patients with Coronary Artery Disease Undergoing Major Noncardiac Surgery. Anesthesiology. 2019;130(5):756\u0026ndash;66.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHallqvist L, Granath F, Fored M, Bell M. Intraoperative Hypotension and Myocardial Infarction Development Among High-Risk Patients Undergoing Noncardiac Surgery: A Nested Case-Control Study. Volume 133. Anesthesia and Analgesia; 2021. 1.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMaheshwari K, Turan A, Mao G, et al. The association of hypotension during non-cardiac surgery, before and after skin incision, with postoperative acute kidney injury: a retrospective cohort analysis. Anaesthesia. 2018;73(10):1223\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eKouz K, Wegge M, Flick M, et al. Continuous intra-arterial versus intermittent oscillometric arterial pressure monitoring and hypotension during induction of anaesthesia: the AWAKE randomised trial. Br J Anaesth. 2022;129(4):478\u0026ndash;86.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHuang S, Liao Z, Chen A, Wang J, Xu X, Zhang L. Effect of carotid corrected flow time combined with perioperative fluid therapy on preventing hypotension after general anesthesia induction in elderly patients: A prospective cohort study. London, England: International Journal of Surgery; 2023.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLestar M, Gunnarsson L, Lagerstrand L, Wiklund P, Odeberg-Wernerman S. Hemodynamic perturbations during robot-assisted laparoscopic radical prostatectomy in 45\u0026deg; Trendelenburg position. Anesth Analg. 2011;113(5):1069\u0026ndash;75.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eDevereaux PJ, Sessler DI, Leslie K. Clonidine in patients undergoing noncardiac surgery. N Engl J Med. 2014;370(16):1504\u0026ndash;13.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWalsh M, Devereaux PJ, Garg AX, et al. Relationship between intraoperative mean arterial pressure and clinical outcomes after noncardiac surgery: toward an empirical definition of hypotension. Anesthesiology. 2013;119(3):507\u0026ndash;15.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSun LY, Wijeysundera DN, Tait GA, Beattie WS. Association of intraoperative hypotension with acute kidney injury after elective noncardiac surgery. Anesthesiology. 2015;123(3):515\u0026ndash;23.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eXing CY, Tarumi T, Meijers RL et al. \u003cem\u003eArterial Pressure, Heart Rate, and Cerebral Hemodynamics Across the Adult Life Span.\u003c/em\u003e Hypertension (Dallas, Tex.: 1979), 2017. 69(4): pp. 712\u0026ndash;720.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eStrandgaard S. Autoregulation of cerebral blood flow in hypertensive patients. The modifying influence of prolonged antihypertensive treatment on the tolerance to acute, drug-induced hypotension. Circulation. 1976;53(4):720\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eRudolph JL, Jones RN, Rasmussen LS, Silverstein JH, Inouye SK, Marcantonio ER. Independent vascular and cognitive risk factors for postoperative delirium. Am J Med. 2007;120(9):807\u0026ndash;13.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eYang L, Sun D, Han J, Liu R, Wang L, Zhang Z. Effects of Intraoperative Hemodynamics on Incidence of Postoperative Delirium in Elderly Patients: A Retrospective Study. Med Sci Monitor: Int Med J Experimental Clin Res. 2016;22:1093\u0026ndash;100.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eScholz AFM, Oldroyd C, McCarthy K, Quinn TJ, Hewitt J. Systematic review and meta-analysis of risk factors for postoperative delirium among older patients undergoing gastrointestinal surgery. Br J Surg. 2015;103(2):e21\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMaheshwari K, Ahuja S, Khanna AK, et al. Association Between Perioperative Hypotension and Delirium in Postoperative Critically Ill Patients: A Retrospective Cohort Analysis. Anesth Analg. 2020;130(3):636\u0026ndash;43.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eYildirim SA, Dogan L, Sarikaya ZT, Ulugol H, Gucyetmez B, Toraman F. Hypotension after Anesthesia Induction: Target-Controlled Infusion Versus Manual Anesthesia Induction of Propofol. J Clin Med, 2023. 12(16).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eChouchou F, Pichot V, Costes F, et al. Autonomic cardiovascular adaptations to acute head-out water immersion, head-down tilt and supine position. Eur J Appl Physiol. 2020;120(2):337\u0026ndash;47.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eFreitas DA, Chaves GS, Santino TA, et al. Standard (head-down tilt) versus modified (without head-down tilt) postural drainage in infants and young children with cystic fibrosis. Cochrane Database Syst Rev. 2018;3(3):CD010297.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Hypotension, Trendelenburg position, Anesthesia induction, Arterial pressure, Gastrointestinal surgery","lastPublishedDoi":"10.21203/rs.3.rs-8146302/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8146302/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e\u003cp\u003eHypotension during general anesthesia induction is common and linked to adverse outcomes. Positioning strategies such as the Trendelenburg position may help improve hemodynamics, but their effectiveness during induction remains unclear.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e\u003cp\u003eThis single-center, prospective, randomized controlled trial was conducted at Zhejiang Cancer Hospital in China from June to August 2024. A total of 70 adult patients (ASA I\u0026ndash;III) scheduled for laparoscopic colorectal or gastric cancer surgery were randomly assigned to either the Trendelenburg group (n\u0026thinsp;=\u0026thinsp;35) or the supine group (n\u0026thinsp;=\u0026thinsp;35). Immediately after loss of eyelash reflex, patients were positioned in a 10\u0026deg; Trendelenburg or supine position for 15 minutes. Standardized anesthesia, fluid therapy, and vasopressor protocols were applied. The primary outcome was the area under the curve (AUC) for mean arterial pressure (MAP)\u0026thinsp;\u0026lt;\u0026thinsp;65 mmHg during the first 15 minutes post-induction. Secondary outcomes included AUC for MAP\u0026thinsp;\u0026lt;\u0026thinsp;60 and \u0026lt;\u0026thinsp;50 mmHg, duration of hypotension, and drug usage. Statistical analyses involved appropriate non-parametric tests to compare the groups.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e\u003cp\u003eThe median AUC for MAP\u0026thinsp;\u0026lt;\u0026thinsp;65 mmHg was 0 (0\u0026ndash;0) mmHg\u0026middot;min in the Trendelenburg group versus 2.03 (0\u0026ndash;5.40) mmHg\u0026middot;min in the supine group (P\u0026thinsp;\u0026lt;\u0026thinsp;0.001). The duration of MAP\u0026thinsp;\u0026lt;\u0026thinsp;65 mmHg was 0 minutes in the Trendelenburg group compared to 0.92 minutes in the supine group (P\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Vasopressor use and remifentanil doses were significantly lower in the Trendelenburg group.\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e\u003cp\u003eApplying a 10\u0026deg; Trendelenburg position during anesthesia induction significantly reduces the incidence and severity of hypotension in patients undergoing gastrointestinal surgery. Larger multicenter studies are warranted to evaluate the impact on postoperative outcomes and recovery.\u003c/p\u003e\u003ch2\u003eTrial registration:\u003c/h2\u003e\u003cp\u003eThe trial was registered on June 3, 2024, at \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://www.chictr.org.cn/\u003c/span\u003e\u003cspan address=\"http://www.chictr.org.cn/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e, registration number ChiCTR2400085213.\u003c/p\u003e","manuscriptTitle":"Effect of Trendelenburg position on post-induction hypotension in patients undergoing gastrointestinal surgery: A Randomized Clinical Trial","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-12-08 12:54:04","doi":"10.21203/rs.3.rs-8146302/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"16c6421d-472e-4afe-86a3-952874a22c13","owner":[],"postedDate":"December 8th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-01-27T10:32:06+00:00","versionOfRecord":[],"versionCreatedAt":"2025-12-08 12:54:04","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8146302","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8146302","identity":"rs-8146302","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}