Gastric ultrasound reveals no association between prolonged fasting duration and gastric residual volume in pediatric patients

Gastric ultrasound reveals no association between prolonged fasting duration and gastric residual volume in pediatric patients | 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 Article Gastric ultrasound reveals no association between prolonged fasting duration and gastric residual volume in pediatric patients Qingda Wu, Bin Liu, Zhouwu Wang, Lingzhi Chen, Hao Liu, Qi Zou, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9079107/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 8 You are reading this latest preprint version Abstract Prolonged preoperative fasting is common in pediatric anesthesia, yet its effect on gastric residual volume (GRV) remains inadequately explored. We conducted a prospective observational cross-sectional study to examine the association between prolonged fasting duration and GRV measured using point-of-care gastric ultrasonography. A total of 491 children aged 1–12 years scheduled for elective surgery under general anesthesia after fasting more than 8 hours were included. GRV was measured using point-of-care gastric ultrasonography and calculated using a validated formula, then normalized to body weight. The primary outcome was the association between fasting duration and weight-adjusted GRV (GRV/WT). Among the participants (median age 89 months; 308 boys), fifteen patients (3.05%) had a full stomach (GRV/WT > 1.25 mL·kg⁻¹) and 29 (5.91%) showed high-risk gastric antrum morphology. Prolonged fasting duration was not associated with GRV/WT. GRV/WT correlated positively with age and negatively with body mass index. These findings suggest that prolonged preoperative fasting does not reliably reduce GRV in pediatric patients. Health sciences/Diseases Health sciences/Gastroenterology Health sciences/Health care Health sciences/Medical research Health sciences/Risk factors Gastric residual volume Fasting Pediatric Gastric ultrasonography Figures Figure 1 Figure 2 Figure 3 Figure 4 Introduction Preoperative fasting is a standard practice aimed at reducing the risk of pulmonary aspiration during anesthesia by limiting gastric volume and acidity. Contemporary guidelines recommend relatively short fasting intervals, particularly for clear fluids, based on physiological gastric emptying models and clinical safety data [ 1 – 4 ]. Despite these recommendations, prolonged fasting remains common in pediatric practice because of operating room delays, scheduling uncertainty, and institution-level conservative policies [ 5 ]. Consequently, many children fast far longer than advised, often exceeding 10–12 hours, raising concerns about both patient comfort and the clinical validity of time-based fasting rules [ 6 – 8 ]. The prevailing assumption that longer fasting reliably translates into a lower gastric residual volume (GRV) has increasingly been questioned [ 9 , 10 ]. Experimental studies indicate that fasting duration alone is an imprecise surrogate for true gastric content status [ 11 , 12 ]. However, most existing work has focused on various fasting durations or guideline-compliant fasting, and data examining the effect of prolonged fasting on sonographically assessed GRV in children remain limited. Point-of-care gastric ultrasonography has emerged as a practical imaging tool for direct, bedside assessment of gastric contents [ 13 ]. This non-invasive technique allows for rapid and accurate evaluation of gastric volume, providing a reliable alternative to traditional methods. This study investigated the association between prolonged fasting duration and GRV, as assessed by point-of-care gastric ultrasonography, in pediatric patients undergoing elective surgery. Methods This prospective, observational, cross-sectional study was approved by the Ethics Committee of the Second Affiliated Hospital of Shantou University Medical College (Approval No. 2024-58) and was prospectively registered with the Chinese Clinical Trial Registry (ChiCTR2400094404). All methods were performed in accordance with the relevant guidelines and regulations. Written informed consent was obtained from the legal guardian of all participants, and assent was obtained from children when appropriate, before any study procedures were performed. Participants We consecutively enrolled pediatric patients aged 1–12 years (12–156 months) with American Society of Anesthesiologists (ASA) physical status I or II, scheduled for elective surgery under general anaesthesia between July 1, 2024, and February 1, 2025. Inclusion Criteria: (1) Age between 1 and 12 years. (2) ASA physical status I or II. (3) Scheduled for elective surgery requiring general anesthesia. (4) At least 8 hours of fasting after a substantial meal. Exclusion Criteria: (1) Medical history of esophageal, gastric, or duodenal surgery, or known gastrointestinal disorders affecting gastric emptying (e.g., gastroparesis, severe gastroesophageal reflux disease). (2) Acute gastrointestinal symptoms (e.g., vomiting, diarrhea) during the study period. (3) Inadequate ultrasonographic visualization of the gastric antrum. (4) Inability to cooperate with the ultrasound examination protocol despite minimal sedation. (5) Refusal to participate by the child or guardian. Study Procedures Upon arrival at the operating room, participants were accompanied by a guardian and monitored for pulse oximetry, non-invasive blood pressure, and electrocardiogram. Supplemental oxygen was administered via face mask at 3–6 L/min. In cases of noncompliance, intravenous midazolam (0.05–0.1 mg/kg) was administered. Sedation depth was assessed using the University of Michigan Sedation Scale (UMSS), and gastric ultrasonography was initiated once a UMSS score of 1–2 was achieved. The ultrasound examination required approximately 3–5 minutes per patient. Gastric ultrasonography Gastric ultrasonography was performed using a portable ultrasound system (Mindray M9, Mindray Bio-Medical Electronics Co., Ltd.). A low-frequency curvilinear probe (2–5 MHz) was initially employed, set at an optimal depth of 6–8 cm. When the gastric antrum was inadequately visualized or located < 3 cm from the skin surface, a high-frequency linear transducer (7–12 MHz) was used instead. Examinations were conducted in both the supine and right lateral decubitus (RLD) positions (Figure 1). The gastric antrum was identified in the epigastric region beneath the left costal margin and imaged in a standardized transverse plane (Figure 2). Three consecutive images were acquired in each position. For sedated participants, positioning assistance was provided by an operating room nurse as required. Gastric contents were evaluated qualitatively using a three-point antral grading system (Table 2), in which Grades 0 and 1 were categorized as low-risk and Grade 2 as high-risk for aspiration. Quantitative assessment included measurement of the cross-sectional area (CSA) of the gastric antrum in the RLD position using the ultrasound system's free-trace caliper function. The mean value of three independent measurements was used for analysis. Gastric residual volume (GRV) was calculated using an age-dependent formula validated in pediatric patients (equation 1). GRV was normalized to body weight to obtain weight-adjusted gastric residual volume (GRV/WT, mL·kg⁻¹). A full stomach was defined as GRV/WT > 1.25 mL·kg⁻¹. All ultrasound examinations were conducted by a single investigator who had completed formal training in gastric ultrasonography and had performed more than 33 supervised examinations prior to study initiation, ensuring consistency and reliability of measurements. Outcome The primary outcome was the association between prolonged fasting duration and GRV/WT in pediatric patients. Statistical Analysis A priori sample size calculation was performed using G*Power software (version 3.1.9.7). Assuming an effect size of 0.5, a two-sided significance level of 0.05, and a statistical power of 80%, a minimum sample of 478 participants was required. To account for potential exclusions, an additional 20% was planned for enrollment. Statistical analyses were conducted using SPSS Statistics (version 27.0, IBM Corp.). Normality of continuous variables was assessed with the Shapiro–Wilk test. Normally distributed data are reported as mean ± standard deviation, and non-normally distributed data as median with interquartile range. Categorical variables are summarized as counts and percentages. Associations between fasting duration and GRV/WT were evaluated using Spearman's rank correlation coefficient (ρ). Group comparisons of continuous variables were performed using the independent-samples t-test or Mann–Whitney U test, as appropriate, and categorical variables were compared using the chi-square test or Fisher's exact test. When multiple comparisons were performed, Bonferroni correction was applied. All statistical tests were two-sided, and a p- value < 0.05 was considered statistically significant. Results A total of 504 pediatric patients were screened. Thirteen patients were excluded owing to inadequate ultrasonographic visualization (n = 7) or inability to cooperate with the examination (n = 6), The final study cohort therefore comprised 491 patients (Figure 3). Baseline demographic and clinical characteristics of the analyzed cohort are summarized in Table 3. Overall, 15 of 491 patients (3.05%) met the predefined criterion for a full stomach, defined as GRV/WT > 1.25 mL·kg⁻¹. A high-risk gastric antrum (Grade 2) was identified in 29 patients (5.91%). Univariate comparisons showed no statistically significant differences in age, sex distribution, body mass index (BMI), or fasting duration between patients with and without a full stomach, or between those with and without a high-risk gastric antrum (all p > 0.05; Table 3). Associations between GRV/WT and key variables are presented in Table 4 and Figure 4. Spearman's rank correlation analysis demonstrated no significant association between GRV/WT and prolonged fasting duration (ρ = 0.037, p = 0.41). GRV/WT showed a positive correlation with age (ρ = 0.223, p < 0.001) and a negative correlation with BMI (ρ = –0.219, p < 0.001). Both correlations remained statistically significant after Bonferroni correction for multiple comparisons (adjusted α = 0.0167). Associations between gastric antrum grade and fasting duration, age, and BMI were assessed using Mann–Whitney U tests (Table 5). No statistically significant differences were observed between low-risk (Grades 0–1) and high-risk (Grade 2) antrum groups for fasting duration (U = 0.073, p = 0.94), age (U = 1.199, p = 0.23), or BMI (U = 0.808, p = 0.42). Discussion In this prospective cross-sectional study, we found that a small but clinically relevant proportion of pediatric patients retained significant gastric contents despite prolonged preoperative fasting exceeding 8 hours. Specifically, 3.05% of children met sonographic criteria for a full stomach based on GRV/WT, and 5.91% exhibited a high-risk gastric antrum (Grade 2). Furthermore, prolonged fasting duration showed no significant association with either quantitative gastric volume or qualitative antral grading. These findings indicate that extending fasting well beyond guideline-recommended intervals does not result in further reduction of gastric contents and that fasting duration alone is an unreliable surrogate for gastric emptiness in pediatric patients. Prior investigations have demonstrated that a subset of fasted patients may still present with substantial gastric contents despite adherence to recommended fasting guidelines [9, 10]. The results of this study are consistent with this evidence in both adult and pediatric populations, showing that excessive fasting does not confer additional reduction in gastric volume. Physiologically, this observation is supported by evidence that basal gastric secretions persist during the interdigestive state under vagal and hormonal regulation, leading to measurable intragastric fluid even in the absence of oral intake [14]. Collectively, gastric content status is determined by multiple physiological factors beyond fasting duration alone, explaining the poor correlation observed in the present cohort. From a perioperative risk assessment perspective, our findings underscore the limitations of a purely time-based fasting strategy and highlight the complementary role of point-of-care gastric ultrasonography. Gastric ultrasound enables real-time, non-invasive evaluation of gastric content type and estimated volume and has been shown to be feasible and reproducible in pediatric patients [13, 15–18]. Previous studies have demonstrated that gastric ultrasound can identify unexpected high-risk gastric states and influence anesthetic management, particularly when fasting history is uncertain or prolonged [13, 16–18], supporting an individualized, physiology-based approach to aspiration risk stratification rather than reliance on fasting duration alone. Several limitations should be acknowledged. First, it was a single-center study, which may limit the generalisability of the findings to other institutions. Second, all gastric ultrasound examinations were performed by a single experienced operator, which ensures consistency but prevents assessment of inter-operator variability [19]. Third, perioperative clinical outcomes such as regurgitation or aspiration were not assessed, as ethical considerations require preventive interventions once a high-risk gastric state is identified. Future multi-center studies incorporating multiple operators and standardized training protocols are warranted to confirm these findings and to further define the role of routine gastric ultrasound in pediatric perioperative care. In conclusion, prolonged fasting time was not associated with gastric residual volume in pediatric patients. These findings question the utility of fasting duration as a surrogate marker for aspiration risk and support the incorporation of gastric ultrasonography into individualised perioperative assessment. Declarations Competing interests The authors declare no competing interests. Funding This study was supported by the Shantou Medical Health Science and Technology Project (CN) (No.72 [2024] − 159). Ethics declarations: Institutional Review Board approval was obtained. Author Contribution Q.W., B.L., Z.W., and L.C. conceived the study.Q.W. and Z.W. collected the data.B.L., L.C., Q.Z., and Y.Z. performed the statistical analysis.H.L. and Z.D. contributed to methodology development.Q.W., B.L., Z.W., and L.C. drafted the manuscript.Q.W. and L.C. revised the manuscript.All authors reviewed and approved the final manuscript. Acknowledgement We are grateful to our colleagues (Department of Anesthesiology, Second Affiliated Hospital of Shantou University Medical College) for their help with sample collection. Data Availability All data supporting the findings of this study are available within this article. References Degeeter, T., Demey, B., Van Caelenberg, E., De Baerdemaeker, L. & Coppens, M. Prospective audit on fasting status of elective ambulatory surgery patients, correlated to gastric ultrasound. Acta chirurgica Belgica. 123(1), 43–48 (2023). Alcarraz, P., et al. Preoperative fasting for the infusion of "yerba mate": a randomized clinical trial with ultrasound evaluation of gastric contents. Brazilian journal of anesthesiology (Elsevier) . 72 (6), 757–761 (2022). Beck, M. H., et al. Real-World Evidence: How Long Do Our Patients Fast?-Results from a Prospective JAGO-NOGGO-Multicenter Analysis on Perioperative Fasting in 924 Patients with Malignant and Benign Gynecological Diseases. Cancers. 15(4), 1311; 10.3390/cancers15041311 (2023). MacDougall, K. A. R., Bushra, S. E. S. & Kannan, S. G. 'Think Drink' approach to minimize unnecessary preoperative fasting: 18 years audit experience. Korean journal of anesthesiology. 78(3), 272–278 (2025). Rüggeberg, A., Meybohm, P. & Nickel, E. A. Preoperative fasting and the risk of pulmonary aspiration-a narrative review of historical concepts, physiological effects, and new perspectives. BJA open. 10, 100282; 10.1016/j.bjao.2024.100282 (2024). Bihani, P., et al. Actual Preoperative Fasting Duration and its Impact on Hunger, Thirst, Blood Glucose, and Parental Satisfaction in Pediatric Patients: A Prospective Observational Study. Journal of Indian Association of Pediatric Surgeons. 30(5), 642–647 (2025). Di Vezza, F., Cacace, C., Sanvitti, M. & Bilotta, F. Preoperative Clear Fluid Fasting Duration and Arterial Hypotension During Anesthesia Induction: A Narrative Review. Journal of clinical medicine. 14(19), 6950; 10.3390/jcm14196950 (2025). Aroonpruksakul, N., et al. The actual duration of preoperative fasting in pediatric patients, and its effects on hunger and thirst: a prospective observational study. Translational pediatrics. 12(2), 146–154; 10.21037/tp-22-358 (2023). Chaitra, T. S., Palta, S., Saroa, R., Jindal, S. & Jain, A. Assessment of residual gastric volume using point-of-care ultrasonography in adult patients who underwent elective surgery. The ultrasound journal. 15(1), 7; 10.1186/s13089-023-00307-8 (2023). Aydın, B. S. & Güldoğan, I. K. Determinants of gastric residual volume before elective surgery in diabetic patients: An observational study. Saudi journal of anaesthesia. 18(2), 167–172 (2024). Wei, Y., Liu, K., Lu, X., Wang, J. & Yao, L. Risk factors for a full stomach assessed by gastric ultrasound in patients undergoing elective caesarean section: a prospective cohort study. BMJ open. 15(12), e106269; 10.1136/bmjopen-2025-106269 (2025). Spencer, A. O., et al. Ultrasound assessment of gastric volume in the fasted pediatric patient undergoing upper gastrointestinal endoscopy: development of a predictive model using endoscopically suctioned volumes. Paediatric anaesthesia. 25(3), 301–308 (2015). Godschalx, V., et al. The role of gastric ultrasound in anaesthesia for emergency surgery: A review and clinical guidance. European journal of anaesthesiology and intensive care. 2(4), e0027; 10.1097/EA9.0000000000000027 (2023). Ruiz, R. F., Jukemura, J., Alves, P. R. A. & Santos, M. E. L. D. Evaluation of pH and residual gastric volume after colon preparation with mannitol: prospective randomized study comparing procedure performed after 3 hours versus 6 hours. Clinics (Sao Paulo, Brazil). 75, e1847 (2020). Evain, J. N., et al. Ultrasound assessment of gastric contents in children before general anaesthesia for acute appendicitis. Anaesthesia. 77(6), 668–673 (2022). Mecoli, M. D., Sahu, K., McSoley, J. W., Aronson, L. A. & Narayanasamy, S. The use of point of care gastric ultrasound and anesthesia management in pediatric patients with preoperative fasting non-adherence scheduled for elective surgical procedures: a retrospective study. BMC anesthesiology. 24(1), 237; 10.1186/s12871-024-02628-0 (2024). van de Putte, P., van Hoonacker, J. & Perlas, A. Gastric ultrasound to guide anesthetic management in elective surgical patients non-compliant with fasting instructions: a retrospective cohort study. Minerva anestesiologica. 84(7), 787–795 (2018). Alakkad, H., et al. Point-of-care ultrasound defines gastric content and changes the anesthetic management of elective surgical patients who have not followed fasting instructions: a prospective case series. Canadian journal of anaesthesia = Journal canadien d'anesthesie. 62(11), 1188–1195 (2015). Arzola, C., Carvalho, J. C., Cubillos, J., Ye, X. Y. & Perlas, A. Anesthesiologists' learning curves for bedside qualitative ultrasound assessment of gastric content: a cohort study. Canadian journal of anaesthesia = Journal canadien d'anesthesie. 60(8), 771–779 (2013). Tables Table 1 University of Michigan Sedation Scale (UMSS) Value Patient state 0 Awake and alert 1 Minimally sedated: tired/sleepy, appropriate response to verbal conversation and/or sound 2 Moderately sedated: somnolent/sleeping, easily aroused with light tactile stimulation or simple verbal command 3 Deeply sedated: deep sleep, arousable only with significant physical stimulation 4 Unarousable Abbreviation: UMSS, University of Michigan Sedation Scale. Table 2 Three-point grading system of the gastric antrum Grade Ultrasonographic appearance 0 No visible fluid in either supine or right lateral decubitus position 1 Fluid visible only in the right lateral decubitus position 2 Fluid visible in both supine and right lateral decubitus positions Table 3 Univariate comparisons of preoperative characteristics between patients with and without full stomach and with and without high-risk gastric antrum. Variable Full stomach High-risk antrum Yes (n=15) No (n=476) p- value Yes (n=29) No (n=462) p- value Sex, (male/female, n) 8/7 300/176 0.45 19/10 289/173 0.75 Age (month) 88 [56–128] 89 [65–122] 0.69 114 [62–127] 88 [64–121] 0.94 BMI (kg·m -2 ) 14.15 [13.42–16.17] 16.00 [14.36–18.79] 0.02 16.26 [14.65–20.57] 15.98 [14.27–18.67] 0.23 Fasting duration (hour) 12.00 [11.50–15.00] 11.60 [10.50–13.00] 0.20 12.00 [10.95–13.00] 11.60 [10.50–13.00] 0.42 Data are presented as median [interquartile range] or counts. Continuous variables were compared using the Mann–Whitney U test; categorical variables were compared using the chi-square test. Abbreviations: BMI, body mass index. Table 4 Associations between weight-adjusted gastric residual volume and key variables. Variables GRV/WT Prolonged fasting duration ρ = 0.037, p = 0.41 Age ρ = 0.223, p < 0.001* BMI ρ = -0.219, p < 0.001* Spearman’ s rank correlation coefficients (ρ) and p -values are shown. An asterisk indicates statistical significance at the Bonferroni-adjusted threshold (α = 0.0167). Abbreviations: GRV/WT, gastric residual volume normalized to body weight; BMI, body mass index. Table 5 Associations between gastric antrum grade and key variables. Variables GRV/WT Prolonged fasting duration U = 0.073, p = 0.94 Age U = 1.199, p = 0.23 BMI U = 0.808, p = 0.42 Mann–Whitney U statistics and corresponding p-values are reported for comparisons between low-risk (Grades 0–1) and high-risk (Grade 2) gastric antrum groups. Abbreviations: BMI, body mass index. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Reviewers agreed at journal 13 May, 2026 Reviews received at journal 04 Apr, 2026 Reviewers agreed at journal 04 Apr, 2026 Reviewers invited by journal 03 Apr, 2026 Editor assigned by journal 31 Mar, 2026 Editor invited by journal 17 Mar, 2026 Submission checks completed at journal 14 Mar, 2026 First submitted to journal 14 Mar, 2026 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-9079107","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":619509779,"identity":"8772252d-33fc-4edc-90d5-b83ca24051ca","order_by":0,"name":"Qingda Wu","email":"","orcid":"","institution":"Second Affiliated Hospital of Shantou University Medical College","correspondingAuthor":false,"prefix":"","firstName":"Qingda","middleName":"","lastName":"Wu","suffix":""},{"id":619509781,"identity":"b4872a12-167f-4ac4-a5c5-15ca1d2a27c3","order_by":1,"name":"Bin Liu","email":"","orcid":"","institution":"Second Affiliated Hospital of Shantou University Medical College","correspondingAuthor":false,"prefix":"","firstName":"Bin","middleName":"","lastName":"Liu","suffix":""},{"id":619509782,"identity":"aeace4b2-1b24-4b65-9323-4ac139b8340a","order_by":2,"name":"Zhouwu Wang","email":"","orcid":"","institution":"Second Affiliated Hospital of Shantou University Medical College","correspondingAuthor":false,"prefix":"","firstName":"Zhouwu","middleName":"","lastName":"Wang","suffix":""},{"id":619509783,"identity":"bda55b0d-fed6-477f-8fba-7f51b042c903","order_by":3,"name":"Lingzhi Chen","email":"","orcid":"","institution":"Second Affiliated Hospital of Shantou University Medical College","correspondingAuthor":false,"prefix":"","firstName":"Lingzhi","middleName":"","lastName":"Chen","suffix":""},{"id":619509784,"identity":"4364b132-4784-4db9-b106-a9d7ec606545","order_by":4,"name":"Hao Liu","email":"","orcid":"","institution":"First Affiliated Hospital of Guangzhou University of Chinese Medicine","correspondingAuthor":false,"prefix":"","firstName":"Hao","middleName":"","lastName":"Liu","suffix":""},{"id":619509785,"identity":"3ad18dfd-c0dd-4aab-b68b-2addbae54dce","order_by":5,"name":"Qi Zou","email":"","orcid":"","institution":"Second Affiliated Hospital of Shantou University Medical College","correspondingAuthor":false,"prefix":"","firstName":"Qi","middleName":"","lastName":"Zou","suffix":""},{"id":619509786,"identity":"86e5c2e0-eb94-4c9c-a00b-92a2e42c40b8","order_by":6,"name":"Yongzhen Zhao","email":"","orcid":"","institution":"Second Affiliated Hospital of Shantou University Medical College","correspondingAuthor":false,"prefix":"","firstName":"Yongzhen","middleName":"","lastName":"Zhao","suffix":""},{"id":619509787,"identity":"5994f94a-3cb1-45ab-a557-f46d9f2fe5f0","order_by":7,"name":"Zhenhao Ding","email":"","orcid":"","institution":"Second Affiliated Hospital of Shantou University Medical College","correspondingAuthor":false,"prefix":"","firstName":"Zhenhao","middleName":"","lastName":"Ding","suffix":""},{"id":619509788,"identity":"ff617b99-81e7-4292-9eef-908472b5fad6","order_by":8,"name":"Lu Chen","email":"","orcid":"","institution":"Second Affiliated Hospital of Shantou University Medical College","correspondingAuthor":false,"prefix":"","firstName":"Lu","middleName":"","lastName":"Chen","suffix":""},{"id":619509789,"identity":"e81a2db2-7766-4fa8-99a8-42cc9e0940cd","order_by":9,"name":"Zhenwei Zheng","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAx0lEQVRIiWNgGAWjYDACZgYGCYYKGzl+9sbGhx+I13ImzViy53CzsQSxFkkwth1O3HAjvU2AhxjlBsd5D95gOMPMOHPmwzagfXZyug2EtBzmS7ZgqGBj5pdObHtQwJBsbHaAgBazwzxmQL/wsEnOTmw3kGA4kLiNKC2MbRI8BjcPAkkStBhIGNxgJFKL/WEeYwuGMwkGkj2JwEA2IMIvkv1nDG8wVPyv72c//vDhhwo7OYJaQID5D5xpQITyUTAKRsEoGAWEAQCAAz8TUd553gAAAABJRU5ErkJggg==","orcid":"","institution":"Second Affiliated Hospital of Shantou University Medical College","correspondingAuthor":true,"prefix":"","firstName":"Zhenwei","middleName":"","lastName":"Zheng","suffix":""}],"badges":[],"createdAt":"2026-03-10 04:53:13","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9079107/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9079107/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":106543608,"identity":"5a3e9990-06f9-4c87-93b4-cc6b45cb245c","added_by":"auto","created_at":"2026-04-09 16:38:07","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":2054281,"visible":true,"origin":"","legend":"\u003cp\u003eParticipants’ positions during ultrasound examinations. “a” shows the supine position; “b” shows the right lateral decubitus position\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-9079107/v1/36a7be83cc2c6c57645d46d4.png"},{"id":106543607,"identity":"6ad9ac39-3891-4adb-94fe-ba61bb249cdc","added_by":"auto","created_at":"2026-04-09 16:38:07","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":664354,"visible":true,"origin":"","legend":"\u003cp\u003eStandard ultrasonographic view of the gastric antrum. The gastric antrum is visualized in the epigastrium, bordered anteriorly by the left lobe of the liver and posteriorly by the superior mesenteric artery and the aorta.\u003c/p\u003e","description":"","filename":"Figure2.png","url":"https://assets-eu.researchsquare.com/files/rs-9079107/v1/0022b65b12b972f7e905cb9c.png"},{"id":106543605,"identity":"3dbdf38d-cdf0-45c1-84b5-fd25def2b523","added_by":"auto","created_at":"2026-04-09 16:38:07","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":128206,"visible":true,"origin":"","legend":"\u003cp\u003eStudy flow diagram illustrating patient screening, exclusions, and final study cohort.\u003c/p\u003e","description":"","filename":"Figure3.png","url":"https://assets-eu.researchsquare.com/files/rs-9079107/v1/a8ad6548ce2673c535d0ae87.png"},{"id":106725620,"identity":"544ff1de-8ed2-4f01-9b29-a2ca694fdce3","added_by":"auto","created_at":"2026-04-12 18:33:10","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":204797,"visible":true,"origin":"","legend":"\u003cp\u003eScatter plot showing the association between weight-adjusted gastric residual volume (GRV/WT) and prolonged fasting duration. Each point represents one patient.\u003c/p\u003e","description":"","filename":"Figure4.png","url":"https://assets-eu.researchsquare.com/files/rs-9079107/v1/9d7dfe91633aceaf3e42b360.png"},{"id":106727384,"identity":"9ecabb52-043f-48ee-a3b3-6ccce6133f8d","added_by":"auto","created_at":"2026-04-12 18:38:51","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3602479,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9079107/v1/2e7acc46-484f-44ad-947f-0ea59229c7b8.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Gastric ultrasound reveals no association between prolonged fasting duration and gastric residual volume in pediatric patients","fulltext":[{"header":"Introduction","content":"\u003cp\u003ePreoperative fasting is a standard practice aimed at reducing the risk of pulmonary aspiration during anesthesia by limiting gastric volume and acidity. Contemporary guidelines recommend relatively short fasting intervals, particularly for clear fluids, based on physiological gastric emptying models and clinical safety data [\u003cspan additionalcitationids=\"CR2 CR3\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Despite these recommendations, prolonged fasting remains common in pediatric practice because of operating room delays, scheduling uncertainty, and institution-level conservative policies [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Consequently, many children fast far longer than advised, often exceeding 10\u0026ndash;12 hours, raising concerns about both patient comfort and the clinical validity of time-based fasting rules [\u003cspan additionalcitationids=\"CR7\" citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe prevailing assumption that longer fasting reliably translates into a lower gastric residual volume (GRV) has increasingly been questioned [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Experimental studies indicate that fasting duration alone is an imprecise surrogate for true gastric content status [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. However, most existing work has focused on various fasting durations or guideline-compliant fasting, and data examining the effect of prolonged fasting on sonographically assessed GRV in children remain limited.\u003c/p\u003e \u003cp\u003ePoint-of-care gastric ultrasonography has emerged as a practical imaging tool for direct, bedside assessment of gastric contents [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. This non-invasive technique allows for rapid and accurate evaluation of gastric volume, providing a reliable alternative to traditional methods. This study investigated the association between prolonged fasting duration and GRV, as assessed by point-of-care gastric ultrasonography, in pediatric patients undergoing elective surgery.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003eThis prospective, observational, cross-sectional study was approved by the Ethics Committee of the Second Affiliated Hospital of Shantou University Medical College (Approval No. 2024-58) and was prospectively registered with the Chinese Clinical Trial Registry (ChiCTR2400094404). All methods were performed in accordance with the relevant guidelines and regulations. Written informed consent was obtained from the legal guardian of all participants, and assent was obtained from children when appropriate, before any study procedures were performed. \u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eParticipants\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe consecutively enrolled pediatric patients aged 1\u0026ndash;12 years (12\u0026ndash;156 months) with American Society of Anesthesiologists (ASA) physical status I or II, scheduled for elective surgery under general anaesthesia between July 1, 2024, and February 1, 2025.\u003c/p\u003e\n\u003cp\u003eInclusion Criteria: (1) Age between 1 and 12 years. (2) ASA physical status I or II. (3) Scheduled for elective surgery requiring general anesthesia. (4)\u0026nbsp;At least 8 hours of fasting\u0026nbsp;after a substantial meal.\u003c/p\u003e\n\u003cp\u003eExclusion Criteria: (1) Medical history of esophageal, gastric, or duodenal surgery, or known gastrointestinal disorders affecting gastric emptying (e.g., gastroparesis, severe gastroesophageal reflux disease). (2) Acute gastrointestinal symptoms (e.g., vomiting, diarrhea) during the study period. (3) Inadequate ultrasonographic visualization of the gastric antrum. (4) Inability to cooperate with the ultrasound examination protocol despite minimal sedation. (5) Refusal to participate by the child or guardian.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eStudy Procedures\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eUpon arrival at the operating room, participants were accompanied by a guardian and monitored for pulse oximetry, non-invasive blood pressure, and electrocardiogram. Supplemental oxygen was administered via face mask at 3\u0026ndash;6 L/min. In cases of noncompliance, intravenous midazolam (0.05\u0026ndash;0.1 mg/kg) was administered. Sedation depth was assessed using the University of Michigan Sedation Scale (UMSS), and gastric ultrasonography was initiated once a UMSS score of 1\u0026ndash;2 was achieved. The ultrasound examination required approximately 3\u0026ndash;5 minutes per patient.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eGastric ultrasonography\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eGastric ultrasonography was performed using a portable ultrasound system (Mindray M9, Mindray Bio-Medical Electronics Co., Ltd.). A low-frequency curvilinear probe (2\u0026ndash;5 MHz) was initially employed, set at an optimal depth of 6\u0026ndash;8 cm. When the gastric antrum was inadequately visualized or located \u0026lt; 3 cm from the skin surface, a high-frequency linear transducer (7\u0026ndash;12 MHz) was used instead.\u003c/p\u003e\n\u003cp\u003eExaminations were conducted in both the supine and right lateral decubitus (RLD) positions (Figure 1). The gastric antrum was identified in the epigastric region beneath the left costal margin and imaged in a standardized transverse plane (Figure 2). Three consecutive images were acquired in each position. For sedated participants, positioning assistance was provided by an operating room nurse as required. Gastric contents were evaluated qualitatively using a three-point antral grading system (Table 2), in which Grades 0 and 1 were categorized as low-risk and Grade 2 as high-risk for aspiration. Quantitative assessment included measurement of the cross-sectional area (CSA) of the gastric antrum in the RLD position using the ultrasound system\u0026apos;s free-trace caliper function. The mean value of three independent measurements was used for analysis. Gastric residual volume (GRV) was calculated using an age-dependent formula validated in pediatric patients (equation 1). GRV was normalized to body weight to obtain weight-adjusted gastric residual volume (GRV/WT, mL\u0026middot;kg⁻\u0026sup1;). A full stomach was defined as GRV/WT \u0026gt; 1.25 mL\u0026middot;kg⁻\u0026sup1;.\u003c/p\u003e\n\u003cp\u003e\u003cimg src=\"https://myfiles.space/user_files/58895_8739fc6c57c1c19a/58895_custom_files/img1775748895.png\" width=\"551\" height=\"87\"\u003e\u003c/p\u003e\n\u003cp\u003eAll ultrasound examinations were conducted by a single investigator who had completed formal training in gastric ultrasonography and had performed more than 33 supervised examinations prior to study initiation, ensuring consistency and reliability of measurements.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eOutcome\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe primary outcome was the association between prolonged fasting duration and GRV/WT in pediatric patients.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eStatistical Analysis\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA priori sample size calculation was performed using G*Power software (version 3.1.9.7). Assuming an effect size of 0.5, a two-sided significance level of 0.05, and a statistical power of 80%, a minimum sample of 478 participants was required. To account for potential exclusions, an additional 20% was planned for enrollment.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eStatistical analyses were conducted using SPSS Statistics (version 27.0, IBM Corp.). Normality of continuous variables was assessed with the Shapiro\u0026ndash;Wilk test. Normally distributed data are reported as mean \u0026plusmn; standard deviation, and non-normally distributed data as median with interquartile range. Categorical variables are summarized as counts and percentages. Associations between fasting duration and GRV/WT were evaluated using Spearman\u0026apos;s rank correlation coefficient (\u0026rho;). Group comparisons of continuous variables were performed using the independent-samples t-test or Mann\u0026ndash;Whitney U test, as appropriate, and categorical variables were compared using the chi-square test or Fisher\u0026apos;s exact test. When multiple comparisons were performed, Bonferroni correction was applied. All statistical tests were two-sided, and a \u003cem\u003ep-\u003c/em\u003evalue \u0026lt; 0.05 was considered statistically significant.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eA total of 504 pediatric patients were screened. Thirteen patients were excluded owing to inadequate ultrasonographic visualization (n = 7) or inability to cooperate with the examination (n = 6), The final study cohort therefore comprised 491 patients (Figure 3). Baseline demographic and clinical characteristics of the analyzed cohort are summarized in Table 3. Overall, 15 of 491 patients (3.05%) met the predefined criterion for a full stomach, defined as GRV/WT \u0026gt; 1.25 mL\u0026middot;kg⁻\u0026sup1;. A high-risk gastric antrum (Grade 2) was identified in 29 patients (5.91%). Univariate comparisons showed no statistically significant differences in age, sex distribution, body mass index (BMI), or fasting duration between patients with and without a full stomach, or between those with and without a high-risk gastric antrum (all \u003cem\u003ep\u003c/em\u003e \u0026gt; 0.05; Table 3).\u003c/p\u003e\n\u003cp\u003eAssociations between GRV/WT and key variables are presented in Table 4 and Figure 4. Spearman\u0026apos;s rank correlation analysis demonstrated no significant association between GRV/WT and prolonged fasting duration (\u0026rho; = 0.037, \u003cem\u003ep\u003c/em\u003e = 0.41). GRV/WT showed a positive correlation with age (\u0026rho; = 0.223, \u003cem\u003ep\u003c/em\u003e \u0026lt; 0.001) and a negative correlation with BMI (\u0026rho; = \u0026ndash;0.219, \u003cem\u003ep\u003c/em\u003e \u0026lt; 0.001). Both correlations remained statistically significant after Bonferroni correction for multiple comparisons (adjusted \u0026alpha; = 0.0167).\u003c/p\u003e\n\u003cp\u003eAssociations between gastric antrum grade and fasting duration, age, and BMI were assessed using Mann\u0026ndash;Whitney U tests (Table 5). No statistically significant differences were observed between low-risk (Grades 0\u0026ndash;1) and high-risk (Grade 2) antrum groups for fasting duration (U = 0.073, \u003cem\u003ep\u003c/em\u003e = 0.94), age (U = 1.199, \u003cem\u003ep\u003c/em\u003e = 0.23), or BMI (U = 0.808, \u003cem\u003ep\u003c/em\u003e = 0.42).\u0026nbsp;\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eIn this prospective cross-sectional study, we found that a small but clinically relevant proportion of pediatric patients retained significant gastric contents despite prolonged preoperative fasting exceeding 8 hours. Specifically, 3.05% of children met sonographic criteria for a full stomach based on GRV/WT, and 5.91% exhibited a high-risk gastric antrum (Grade 2). Furthermore, prolonged fasting duration showed no significant association with either quantitative gastric volume or qualitative antral grading. These findings indicate that extending fasting well beyond guideline-recommended intervals does not result in further reduction of gastric contents and that fasting duration alone is an unreliable surrogate for gastric emptiness in pediatric patients.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003ePrior investigations have demonstrated that a subset of fasted patients may still present with substantial gastric contents despite adherence to recommended fasting guidelines [9, 10]. The results of this study are consistent with this evidence in both adult and pediatric populations, showing that excessive fasting does not confer additional reduction in gastric volume. Physiologically, this observation is supported by evidence that basal gastric secretions persist during the interdigestive state under vagal and hormonal regulation, leading to measurable intragastric fluid even in the absence of oral intake [14]. Collectively, gastric content status is determined by multiple physiological factors beyond fasting duration alone, explaining the poor correlation observed in the present cohort. From a perioperative risk assessment perspective, our findings underscore the limitations of a purely time-based fasting strategy and highlight the complementary role of point-of-care gastric ultrasonography. Gastric ultrasound enables real-time, non-invasive evaluation of gastric content type and estimated volume and has been shown to be feasible and reproducible in pediatric patients [13, 15\u0026ndash;18]. Previous studies have demonstrated that gastric ultrasound can identify unexpected high-risk gastric states and influence anesthetic management, particularly when fasting history is uncertain or prolonged [13, 16\u0026ndash;18], supporting an individualized, physiology-based approach to aspiration risk stratification rather than reliance on fasting duration alone.\u003c/p\u003e\n\u003cp\u003eSeveral limitations should be acknowledged. First, it was a single-center study, which may limit the generalisability of the findings to other institutions. Second, all gastric ultrasound examinations were performed by a single experienced operator, which ensures consistency but prevents assessment of inter-operator variability [19]. Third, perioperative clinical outcomes such as regurgitation or aspiration were not assessed, as ethical considerations require preventive interventions once a high-risk gastric state is identified. Future multi-center studies incorporating multiple operators and standardized training protocols are warranted to confirm these findings and to further define the role of routine gastric ultrasound in pediatric perioperative care.\u003c/p\u003e\n\u003cp\u003eIn conclusion, prolonged fasting time was not associated with gastric residual volume in pediatric patients. These findings question the utility of fasting duration as a surrogate marker for aspiration risk and support the incorporation of gastric ultrasonography into individualised perioperative assessment.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eCompeting interests\u003c/h2\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003ch2\u003eFunding\u003c/h2\u003e\n\u003cp\u003eThis study was supported by the Shantou Medical Health Science and Technology Project (CN) (No.72 [2024]\u0026thinsp;\u0026minus;\u0026thinsp;159).\u003c/p\u003e\n\u003ch2\u003eEthics declarations:\u003c/h2\u003e\n\u003cp\u003eInstitutional Review Board approval was obtained.\u003c/p\u003e\n\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\n\u003cp\u003eQ.W., B.L., Z.W., and L.C. conceived the study.Q.W. and Z.W. collected the data.B.L., L.C., Q.Z., and Y.Z. performed the statistical analysis.H.L. and Z.D. contributed to methodology development.Q.W., B.L., Z.W., and L.C. drafted the manuscript.Q.W. and L.C. revised the manuscript.All authors reviewed and approved the final manuscript.\u003c/p\u003e\n\u003ch2\u003eAcknowledgement\u003c/h2\u003e\n\u003cp\u003eWe are grateful to our colleagues (Department of Anesthesiology, Second Affiliated Hospital of Shantou University Medical College) for their help with sample collection.\u003c/p\u003e\n\u003ch2\u003eData Availability\u003c/h2\u003e\n\u003cp\u003eAll data supporting the findings of this study are available within this article.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eDegeeter, T., Demey, B., Van Caelenberg, E., De Baerdemaeker, L. \u0026amp; Coppens, M. 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The use of point of care gastric ultrasound and anesthesia management in pediatric patients with preoperative fasting non-adherence scheduled for elective surgical procedures: a retrospective study. \u003cem\u003eBMC anesthesiology.\u003c/em\u003e \u003cstrong\u003e24(1),\u003c/strong\u003e 237; 10.1186/s12871-024-02628-0 (2024).\u003c/li\u003e\n\u003cli\u003evan de Putte, P., van Hoonacker, J. \u0026amp; Perlas, A. Gastric ultrasound to guide anesthetic management in elective surgical patients non-compliant with fasting instructions: a retrospective cohort study.\u003cem\u003e Minerva anestesiologica.\u003c/em\u003e \u003cstrong\u003e84(7),\u003c/strong\u003e 787\u0026ndash;795 (2018).\u003c/li\u003e\n\u003cli\u003eAlakkad, H., et al. Point-of-care ultrasound defines gastric content and changes the anesthetic management of elective surgical patients who have not followed fasting instructions: a prospective case series. \u003cem\u003eCanadian journal of anaesthesia = Journal canadien d\u0026apos;anesthesie.\u003c/em\u003e \u003cstrong\u003e62(11),\u003c/strong\u003e 1188\u0026ndash;1195 (2015). \u003c/li\u003e\n\u003cli\u003eArzola, C., Carvalho, J. C., Cubillos, J., Ye, X. Y. \u0026amp; Perlas, A. Anesthesiologists\u0026apos; learning curves for bedside qualitative ultrasound assessment of gastric content: a cohort study. \u003cem\u003eCanadian journal of anaesthesia = Journal canadien d\u0026apos;anesthesie. \u003c/em\u003e\u003cstrong\u003e60(8),\u003c/strong\u003e 771\u0026ndash;779 (2013).\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003e\u003cstrong\u003eTable\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003e1\u003c/strong\u003e University of Michigan Sedation Scale (UMSS)\u003c/p\u003e\n\u003cdiv align=\"\"\u003e\n \u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"609\"\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 46px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eValue\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 562px;\"\u003e\n \u003cp\u003e\u003cstrong\u003ePatient state\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 46px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 562px;\"\u003e\n \u003cp\u003eAwake and alert\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 46px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 562px;\"\u003e\n \u003cp\u003eMinimally sedated: tired/sleepy, appropriate response to verbal conversation and/or sound\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 46px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 562px;\"\u003e\n \u003cp\u003eModerately sedated: somnolent/sleeping, easily aroused with light tactile stimulation or simple verbal command\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 46px;\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 562px;\"\u003e\n \u003cp\u003eDeeply sedated: deep sleep, arousable only with significant physical stimulation\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 46px;\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 562px;\"\u003e\n \u003cp\u003eUnarousable\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eAbbreviation: UMSS, University of Michigan Sedation Scale.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 2\u003c/strong\u003e Three-point grading system of the gastric antrum\u003c/p\u003e\n\u003cdiv align=\"\"\u003e\n \u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"568\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 77px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eGrade\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 491px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eUltrasonographic appearance\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 77px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 491px;\"\u003e\n \u003cp\u003eNo visible fluid in either supine or right lateral decubitus position\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 77px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 491px;\"\u003e\n \u003cp\u003eFluid visible only in the right lateral decubitus position\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 77px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 491px;\"\u003e\n \u003cp\u003eFluid visible in both supine and right lateral decubitus positions\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 3\u003c/strong\u003e Univariate comparisons of preoperative characteristics between patients with and without full stomach and with and without high-risk gastric antrum.\u003c/p\u003e\n\u003cdiv align=\"\"\u003e\n \u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"576\"\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" style=\"width: 128px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eVariable\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"3\" style=\"width: 52px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eFull stomach\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"3\" style=\"width: 52px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eHigh-risk antrum\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 86px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eYes (n=15)\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 87px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eNo (n=476)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 52px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003ep-\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003evalue\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 84px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eYes (n=29)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 87px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eNo (n=462)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 52px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003ep-\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003evalue\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 128px;\"\u003e\n \u003cp\u003eSex, (male/female, n)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 86px;\"\u003e\n \u003cp\u003e8/7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 87px;\"\u003e\n \u003cp\u003e300/176\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 52px;\"\u003e\n \u003cp\u003e0.45\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 84px;\"\u003e\n \u003cp\u003e19/10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 87px;\"\u003e\n \u003cp\u003e289/173\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 52px;\"\u003e\n \u003cp\u003e0.75\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 128px;\"\u003e\n \u003cp\u003eAge (month)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 86px;\"\u003e\n \u003cp\u003e88\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e[56\u0026ndash;128]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 87px;\"\u003e\n \u003cp\u003e89\u003c/p\u003e\n \u003cp\u003e[65\u0026ndash;122]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 52px;\"\u003e\n \u003cp\u003e0.69\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 84px;\"\u003e\n \u003cp\u003e114\u003c/p\u003e\n \u003cp\u003e[62\u0026ndash;127]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 87px;\"\u003e\n \u003cp\u003e88\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e[64\u0026ndash;121]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 52px;\"\u003e\n \u003cp\u003e0.94\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 128px;\"\u003e\n \u003cp\u003eBMI (kg\u0026middot;m\u003csup\u003e-2\u003c/sup\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 86px;\"\u003e\n \u003cp\u003e14.15\u003c/p\u003e\n \u003cp\u003e[13.42\u0026ndash;16.17]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 87px;\"\u003e\n \u003cp\u003e16.00\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e[14.36\u0026ndash;18.79]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 52px;\"\u003e\n \u003cp\u003e0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 84px;\"\u003e\n \u003cp\u003e16.26\u003c/p\u003e\n \u003cp\u003e[14.65\u0026ndash;20.57]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 87px;\"\u003e\n \u003cp\u003e15.98\u003c/p\u003e\n \u003cp\u003e[14.27\u0026ndash;18.67]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 52px;\"\u003e\n \u003cp\u003e0.23\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 128px;\"\u003e\n \u003cp\u003eFasting duration (hour)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 86px;\"\u003e\n \u003cp\u003e12.00\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e[11.50\u0026ndash;15.00]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 87px;\"\u003e\n \u003cp\u003e11.60\u003c/p\u003e\n \u003cp\u003e[10.50\u0026ndash;13.00]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 52px;\"\u003e\n \u003cp\u003e0.20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 84px;\"\u003e\n \u003cp\u003e12.00\u003c/p\u003e\n \u003cp\u003e[10.95\u0026ndash;13.00]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 87px;\"\u003e\n \u003cp\u003e11.60\u003c/p\u003e\n \u003cp\u003e[10.50\u0026ndash;13.00]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 52px;\"\u003e\n \u003cp\u003e0.42\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eData are presented as median [interquartile range] or counts. Continuous variables were compared using the Mann\u0026ndash;Whitney U test; categorical variables were compared using the chi-square test.\u003c/p\u003e\n\u003cp\u003eAbbreviations: BMI, body mass index.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 4\u003c/strong\u003e Associations between weight-adjusted gastric residual volume and key variables.\u003c/p\u003e\n\u003cdiv align=\"\"\u003e\n \u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"554\"\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 295px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eVariables\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 259px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eGRV/WT\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 295px;\"\u003e\n \u003cp\u003eProlonged fasting duration\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 259px;\"\u003e\n \u003cp\u003e\u0026rho; = 0.037,\u003cem\u003e\u0026nbsp;p\u0026nbsp;\u003c/em\u003e= 0.41\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 295px;\"\u003e\n \u003cp\u003eAge\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 259px;\"\u003e\n \u003cp\u003e\u0026rho; = 0.223, \u003cem\u003ep\u0026nbsp;\u003c/em\u003e\u0026lt; 0.001*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 295px;\"\u003e\n \u003cp\u003eBMI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 259px;\"\u003e\n \u003cp\u003e\u0026rho; = -0.219, \u003cem\u003ep\u003c/em\u003e \u0026lt; 0.001*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eSpearman\u0026rsquo; s rank correlation coefficients (\u0026rho;) and \u003cem\u003ep\u003c/em\u003e-values are shown.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAn asterisk indicates statistical significance at the Bonferroni-adjusted threshold (\u0026alpha; = 0.0167).\u003c/p\u003e\n\u003cp\u003eAbbreviations: GRV/WT, gastric residual volume normalized to body weight; BMI, body mass index.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 5\u003c/strong\u003e Associations between gastric antrum grade and key variables.\u003c/p\u003e\n\u003cdiv align=\"\"\u003e\n \u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"554\"\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 295px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eVariables\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 259px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eGRV/WT\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 295px;\"\u003e\n \u003cp\u003eProlonged fasting duration\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 259px;\"\u003e\n \u003cp\u003eU = 0.073,\u003cem\u003e\u0026nbsp;p\u0026nbsp;\u003c/em\u003e= 0.94\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 295px;\"\u003e\n \u003cp\u003eAge\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 259px;\"\u003e\n \u003cp\u003eU = 1.199, \u003cem\u003ep =\u003c/em\u003e 0.23\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 295px;\"\u003e\n \u003cp\u003eBMI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 259px;\"\u003e\n \u003cp\u003eU = 0.808, \u003cem\u003ep\u003c/em\u003e = 0.42\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eMann\u0026ndash;Whitney U statistics and corresponding p-values are reported for comparisons between low-risk (Grades 0\u0026ndash;1) and high-risk (Grade 2) gastric antrum groups.\u003c/p\u003e\n\u003cp\u003eAbbreviations: BMI, body mass index.\u0026nbsp;\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"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":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Gastric residual volume , Fasting , Pediatric , Gastric ultrasonography","lastPublishedDoi":"10.21203/rs.3.rs-9079107/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9079107/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eProlonged preoperative fasting is common in pediatric anesthesia, yet its effect on gastric residual volume (GRV) remains inadequately explored. We conducted a prospective observational cross-sectional study to examine the association between prolonged fasting duration and GRV measured using point-of-care gastric ultrasonography. A total of 491 children aged 1\u0026ndash;12 years scheduled for elective surgery under general anesthesia after fasting more than 8 hours were included. GRV was measured using point-of-care gastric ultrasonography and calculated using a validated formula, then normalized to body weight. The primary outcome was the association between fasting duration and weight-adjusted GRV (GRV/WT). Among the participants (median age 89 months; 308 boys), fifteen patients (3.05%) had a full stomach (GRV/WT\u0026thinsp;\u0026gt;\u0026thinsp;1.25 mL\u0026middot;kg⁻\u0026sup1;) and 29 (5.91%) showed high-risk gastric antrum morphology. Prolonged fasting duration was not associated with GRV/WT. GRV/WT correlated positively with age and negatively with body mass index. These findings suggest that prolonged preoperative fasting does not reliably reduce GRV in pediatric patients.\u003c/p\u003e","manuscriptTitle":"Gastric ultrasound reveals no association between prolonged fasting duration and gastric residual volume in pediatric patients","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-04-09 16:38:02","doi":"10.21203/rs.3.rs-9079107/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"308190676839891029210950024199295289292","date":"2026-05-13T18:12:02+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-04-04T22:35:24+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"121163872158569487752121868097030675633","date":"2026-04-04T07:08:01+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-04-03T08:01:15+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-03-31T23:44:21+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2026-03-18T03:05:04+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-03-14T14:24:31+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2026-03-14T14:18:33+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"6ac9e91b-3eb8-49d2-9039-6d3e949251de","owner":[],"postedDate":"April 9th, 2026","published":true,"recentEditorialEvents":[{"type":"reviewerAgreed","content":"308190676839891029210950024199295289292","date":"2026-05-13T18:12:02+00:00","index":63,"fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[{"id":65920909,"name":"Health sciences/Diseases"},{"id":65920910,"name":"Health sciences/Gastroenterology"},{"id":65920911,"name":"Health sciences/Health care"},{"id":65920912,"name":"Health sciences/Medical research"},{"id":65920913,"name":"Health sciences/Risk factors"}],"tags":[],"updatedAt":"2026-04-09T16:38:03+00:00","versionOfRecord":[],"versionCreatedAt":"2026-04-09 16:38:02","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9079107","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9079107","identity":"rs-9079107","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}