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ObesityNCT07032207

Correlation of Preoperative Gastric Residual Volume With Body Mass Index and Aspiration Risk in Laparoscopic Bariatric Surgery

An observational study of Obesity and Gastric Ultrasound, run by Fatih Sultan Mehmet Training and Research Hospital at 1 site in Turkey (Türkiye).

Completed

Finished. The study has ended and is not enrolling. Results may be posted on the official record.

Official record
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Trial summary

Obesity is a chronic, complex disease defined by the World Health Organization (WHO) as the excessive accumulation of fat in the body that can harm health. Since 1975, the prevalence of obesity has been increasing worldwide, making it a significant public health issue. Read more about this study

Who is it for?
Ages 18 to 65 years
How many people
60 participants
Where
1 siteTurkey (Türkiye)
Study dates
30 Jun 2024to 15 Apr 2026
Phase
Observational
Are there results?
None posted in the registry

Key requirements

Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.

  • Ages 18 to 65 years
  • All sexes
  • No healthy volunteers
  • Adult, Older adult

Study population: Patients who will undergo bariatric surgery under general anesthesia in elective conditions

Who may be able to join

  • Patients who will undergo bariatric surgery under general anesthesia in elective conditions
  • Patients in ASA II-III groups, with BMI > 35 kg/m², and aged between 18-65 years
  • Patients who have provided informed consent

Who cannot join

  • Patients under 18 years of age, over 65 years of age, or in ASA IV-V groups
  • Pregnancy
  • Patients with upper gastrointestinal (GI) abnormalities such as hiatal hernia and gastric tumors
  • Patients with a recent history of upper GI bleeding (within the last 12 months), previous stomach and esophagus surgeries, or abnormal anatomy of the upper gastrointestinal tract
  • Patients using medications that affect gastric motility or other related conditions
  • Patients with uncontrolled diabetes
Show all 9Show fewer
  • Patients who require emergency surgery
  • Patients with advanced cardiac, renal, pulmonary, or hepatic failure
  • Patients who refuse to participate and do not provide informed consent

Trial locations and contacts

1 site in 1 country.

Turkey (Türkiye)1 site
  • Fatih Sultan Mehmet Training and Research Hospital

    Istanbul, Istanbul, 34752

Other trials in Turkey (Türkiye)

About this study

Official title: The Correlation of Gastric Residual Volume Detected by Preoperative Gastric Ultrasonography With Body Mass Index and Aspiration Risk in Patients Undergoing Laparoscopic Bariatric Surgery

Obesity is a chronic, complex disease defined by the World Health Organization (WHO) as the excessive accumulation of fat in the body that can harm health. Since 1975, the prevalence of obesity has been increasing worldwide, making it a significant public health issue. Body mass index (BMI) is important in diagnosing obesity. BMI is calculated by dividing a person's weight (kg) by the square of their height (m²). BMI: weight (kg) / height² (m²). According to the WHO, a BMI between 30.0-34.9 kg/m² is classified as Class 1 obesity, between 35.0-39.9 kg/m² as Class 2 obesity, between 40-49.9 kg/m² as Class 3 obesity, and ≥50.0 kg/m² as super obesity.

Obesity is closely related to increasing morbidity and mortality worldwide, and in obese patients, the incidence of diseases such as type 2 diabetes, hypertension, cardiovascular disease, dyslipidemia, coronary heart disease, obstructive sleep apnea, asthma, depression, other psychiatric disorders, and gastroesophageal reflux has increased. Treatment options for obesity include lifestyle changes, specific diets, diet-drug combinations, metabolic and various bariatric surgical options. Among these treatment options, metabolic and bariatric surgical procedures are considered the most effective methods for weight loss.

Read more

Aspiration of gastric contents is a significant perioperative complication that can cause up to 9% of anesthesia-related deaths. Due to delayed gastric emptying in obese patients, the risk of aspiration is higher compared to non-obese patients. In obese patients, preoperative anesthesia management is more challenging, and the risk of pulmonary aspiration is greater. Since obesity is an independent risk factor for patients with a full stomach, and airway management can be difficult in these patients, it is essential to assess the aspiration risk in the preoperative period.

Anesthesia guidelines recommend that to improve the quality and effectiveness of anesthesia care and reduce the severity of potential complications related to perioperative pulmonary aspiration of gastric contents, adults and children should be allowed to drink clear liquids up to 2 hours before elective surgery, and solid food consumption should be prohibited 6 hours before elective surgery.

Recently, with the integration of ultrasound into anesthesia practice, ultrasound has been applied in various surgical procedures and clinical conditions. The use of ultrasound to evaluate the risk of aspiration in the preoperative period and to determine the residual gastric volume is increasingly being used in clinical practice. The use of gastric ultrasound to assess aspiration risk has also been increasing in pediatric patient groups and pregnant patients, similar to obese patient groups.

In this study, the investigators' aim is to determine the relationship between BMI, fasting duration, and aspiration risk by assessing the gastric residual volume in the preoperative period through gastric ultrasonography in patients with obesity who will undergo bariatric surgery.

Read the detailed description

Patients will be informed about the study procedure one day before the surgery, and informed consent will be obtained from those who agree to participate. For patients who have given consent, gastric ultrasonography will be performed in the anesthesia preparation room before surgery. The examination will be conducted first in the supine position and then in the right lateral decubitus (RLD) position.

While patients are in the RLD and supine positions, a low-frequency (2-5 MHz) curved ultrasound probe will be used to scan from left to right along the subcostal margin. The left lobe of the liver and the descending abdominal aorta will be used as anterior and posterior landmarks. Gastric content will be evaluated both qualitatively and quantitatively by gastric ultrasonography.

In the RLD position, two maximum perpendicular diameters of the stomach-anteroposterior (AP) and craniocaudal (CC)-will be measured. The antral cross-sectional area (CSA) in the right lateral decubitus position will be calculated using the formula:

CSA = (AP × CC × π) / 4.

Gastric residual volume will then be calculated using the formula by Perlas et al.:

Gastric residual volume (mL) = 27.0 + 14.6 × right lateral CSA - 1.28 × age.

Patients with an empty antrum and gastric residual volume less than 1.5 mL/kg will be considered at low risk for aspiration, whereas those with solid content and/or gastric residual volume greater than 1.5 mL/kg will be considered high risk for aspiration. A flat antrum image with anterior and posterior walls adjacent will be regarded as an empty stomach. A hypoechoic, thin-walled, distended antrum will be interpreted as liquid content, and a distended antrum showing mixed echogenicity on ultrasound will be considered solid content.

Additionally, the antrum will be classified using a three-point grading system:

Grade 0: No fluid visible in both supine and RLD positions.

Grade 1: Clear fluid visible only in the RLD position.

Grade 2: Fluid and solid content visible in both supine and RLD positions.

All measurements will be repeated three times, and the average will be taken. The duration of the ultrasonography procedure will be recorded.

Preoperative laboratory values including fasting blood glucose, HbA1c, renal function tests (urea, creatinine), liver function tests (AST, ALT), serum electrolytes (sodium, potassium, chloride, calcium), hemogram parameters (hemoglobin, hematocrit, platelet, leukocyte), and coagulation parameters (APTT, INR) will be documented.

Demographic data (age, gender, height, weight), BMI, waist circumference, xiphoid circumference, ASA score, comorbidities, previous surgeries, and ongoing medications will also be recorded.

After completing the gastric ultrasonography, patients will be taken to the operating room. Standard monitoring including electrocardiogram (ECG), non-invasive blood pressure, peripheral oxygen saturation (SpO2), and bispectral index (BIS) will be applied. Premedication will be performed with intravenous midazolam 0.02 mg/kg, followed by preoxygenation with 100% oxygen via mask for 3 minutes.

Standard anesthesia induction will be carried out using intravenous propofol 2-2.5 mg/kg, fentanyl 2 mcg/kg, and rocuronium 0.6 mg/kg. Orotracheal intubation will be performed once adequate muscle relaxation is achieved. Mechanical ventilation will be provided in volume control mode with tidal volumes of 6-8 ml/kg and end-tidal carbon dioxide (EtCO2) maintained between 35-40 mmHg.

Anesthesia maintenance will be ensured with sevoflurane 1.5-2% in 2 L/min of 50% oxygen-air mixture and intravenous remifentanil infusion at 0.05-0.5 mcg/kg/min, targeting BIS values between 40-60. Normothermia will be maintained intraoperatively with active forced-air warming devices in all patients.

Perioperative aspiration events will be recorded as "occurred" or "not occurred." Total surgical and anesthesia durations will be documented.

Twenty minutes before the end of surgery, patients will receive postoperative analgesia prophylaxis with intravenous administration of 1 g paracetamol, 1 mg/kg tramadol, and 4 mg ondansetron for nausea and vomiting prophylaxis, according to our standard protocol.

At the end of surgery, anesthetic agents will be discontinued, and the awakening phase will begin. After patients resume spontaneous respiration, neuromuscular blockade will be reversed with intravenous sugammadex 2 mg/kg. Patients with adequate respiratory effort and BIS ≥ 85 will be extubated and transferred to the recovery unit once they are awake, have regained muscle strength, and are hemodynamically stable.

Postoperative nausea will be evaluated at 1, 6, and 24 hours using a 5-point nausea-vomiting severity scale (0 = no nausea, 1 = mild nausea without vomiting, 2 = moderate nausea with vomiting, 3 = vomiting less than twice per hour, 4 = vomiting more than twice per hour) and any complications will be recorded (present/absent).

Keywords
obesity, gastric ultrasound, gastric residual volume, body mass index, aspiration
Medical subject headings
Obesity

What is being measured

The primary outcome is the main question the study is designed to answer.

  1. The correlation between BMI, gastric residual volume, and aspiration risk.

    Higher BMI levels may be associated with increased gastric residual volume (GRV), which in turn can elevate the risk of pulmonary aspiration, especially during anesthesia. Understanding the correlation between BMI, GRV, and aspiration risk is crucial for developing safer preoperative fasting guidelines and optimizing care in high-risk patients.

    Measured: 5 minutes

Secondary outcomes (1)
  1. The correlation between fasting duration, gastric residual volume, and the risk of aspiration

    Understanding this correlation is crucial in clinical settings, especially in anesthesia, as prolonged fasting may not always reduce gastric volume or aspiration risk. The goal is to optimize preoperative fasting time to enhance patient safety and comfort while minimizing complications related to aspiration.

    Measured: 5 minutes

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

  1. First posted22 Jun 2025
  2. Study start30 Jun 2024
  3. Primary completion30 Apr 2025
  4. Study completion15 Apr 2026

Resources

More details

For doctors and researchers: how the study is designed, who runs it, and its registry IDs.

Study design
Study type
Observational
Observational model
Cohort
Time perspective
Prospective
Enrolment
60 participants (actual)
IDs, dates and publications
ClinicalTrials.gov ID
NCT07032207
Sponsor's protocol ID
FSMTRH-BT01
Status last verified
Apr 2026
First submitted
19 May 2025
Last updated
12 Jun 2026
Results posted
No
Data monitoring committee
No
FDA-regulated drug
No
FDA-regulated device
No
Individual data sharing
No

Publications

  • Sherwin M, Katz D. Using gastric ultrasound to assess gastric content in the pregnant patient. BJA Educ. 2021 Nov;21(11):404-407. doi: 10.1016/j.bjae.2021.08.001. Epub 2021 Sep 23. No abstract available.

    PubMed 34707884
  • Moake MM, Presley BC, Hill JG, Wolf BJ, Kane ID, Busch CE, Jackson BF. Point-of-Care Ultrasound to Assess Gastric Content in Pediatric Emergency Department Procedural Sedation Patients. Pediatr Emerg Care. 2022 Jan 1;38(1):e178-e186. doi: 10.1097/PEC.0000000000002198.

    PubMed 32769837
  • Smith I, Kranke P, Murat I, Smith A, O'Sullivan G, Soreide E, Spies C, in't Veld B; European Society of Anaesthesiology. Perioperative fasting in adults and children: guidelines from the European Society of Anaesthesiology. Eur J Anaesthesiol. 2011 Aug;28(8):556-69. doi: 10.1097/EJA.0b013e3283495ba1.

    PubMed 21712716
  • Bouvet L, Desgranges FP, Aubergy C, Boselli E, Dupont G, Allaouchiche B, Chassard D. Prevalence and factors predictive of full stomach in elective and emergency surgical patients: a prospective cohort study. Br J Anaesth. 2017 Mar 1;118(3):372-379. doi: 10.1093/bja/aew462.

    PubMed 28203726
  • Mahajan V, Hashmi J, Singh R, Samra T, Aneja S. Comparative evaluation of gastric pH and volume in morbidly obese and lean patients undergoing elective surgery and effect of aspiration prophylaxis. J Clin Anesth. 2015 Aug;27(5):396-400. doi: 10.1016/j.jclinane.2015.03.004. Epub 2015 Apr 30.

    PubMed 25935831
  • Perlas A, Chan VW, Lupu CM, Mitsakakis N, Hanbidge A. Ultrasound assessment of gastric content and volume. Anesthesiology. 2009 Jul;111(1):82-9. doi: 10.1097/ALN.0b013e3181a97250.

    PubMed 19512861
  • Singhal V, Youssef S, Misra M. Use of sleeve gastrectomy in adolescents and young adults with severe obesity. Curr Opin Pediatr. 2020 Aug;32(4):547-553. doi: 10.1097/MOP.0000000000000927.

    PubMed 32692052
  • Aaseth J, Ellefsen S, Alehagen U, Sundfor TM, Alexander J. Diets and drugs for weight loss and health in obesity - An update. Biomed Pharmacother. 2021 Aug;140:111789. doi: 10.1016/j.biopha.2021.111789. Epub 2021 May 31.

    PubMed 34082399
  • Ruban A, Stoenchev K, Ashrafian H, Teare J. Current treatments for obesity. Clin Med (Lond). 2019 May;19(3):205-212. doi: 10.7861/clinmedicine.19-3-205.

    PubMed 31092512
  • De Lorenzo A, Gratteri S, Gualtieri P, Cammarano A, Bertucci P, Di Renzo L. Why primary obesity is a disease? J Transl Med. 2019 May 22;17(1):169. doi: 10.1186/s12967-019-1919-y.

    PubMed 31118060
  • Schetz M, De Jong A, Deane AM, Druml W, Hemelaar P, Pelosi P, Pickkers P, Reintam-Blaser A, Roberts J, Sakr Y, Jaber S. Obesity in the critically ill: a narrative review. Intensive Care Med. 2019 Jun;45(6):757-769. doi: 10.1007/s00134-019-05594-1. Epub 2019 Mar 19.

    PubMed 30888440

Questions about this trial

What is this clinical trial studying?

An observational study of Obesity and Gastric Ultrasound, run by Fatih Sultan Mehmet Training and Research Hospital at 1 site in Turkey (Türkiye).

The full registered description is in the About this study section and the official record.

Who may be eligible to take part?

The sponsor lists 3 inclusion and 9 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.

Is this clinical trial currently recruiting?

The record says: finished, as of the sponsor's last update on 12 Jun 2026. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 1 site in Turkey (Türkiye). Whether a site is taking part right now should be confirmed with that site. See every site.

What are the possible benefits and risks?

They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.

Are results available for this study?

The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.

How can a doctor refer a patient or contact the research team?

The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

The correlation between BMI, gastric residual volume, and aspiration risk. (time frame: 5 minutes). It is what the study was designed to measure, not a finding.

Where can I read the original study information?

On the ClinicalTrials.gov record for NCT07032207, which also lists 11 linked publications.

Does a listing mean the treatment is approved or proven to work?

No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.

How often is this information updated?

AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 12 Jun 2026.

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