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NCT Number: NCT07662538

Optic Nerve Sheath Diameter Changes During Bariatric Surgery

This prospective clinical study aimed to evaluate the effects of pneumoperitoneum and patient positioning on intracranial pressure in patients undergoing bariatric surgery. Intracranial pressure was assessed noninvasively using ultrasonographic optic nerve sheath diameter (ONSD) measurements. ONSD measurements were performed before anesthesia induction in the supine position (T0), 5 minutes after anesthesia induction (T1), 5 minutes after creation of pneumoperitoneum and placement in the reverse Trendelenburg position (T2), at the 20th minute of pneumoperitoneum (T3), and 5 minutes after termination of pneumoperitoneum and return to the supine position (T4). The study aimed to determine the effects of anesthesia, pneumoperitoneum, and surgical positioning on intracranial pressure during bariatric surgery

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Key information

Conditions

Morbid Obesity Body Weight Digestive System Diseases Nutrition Disorders Nutritional and Metabolic Diseases Obesity Obesity, Morbid Overnutrition Overweight Pathological Conditions, Signs and Symptoms Peritoneal Diseases Pneumoperitoneum Signs and Symptoms

Age range

18 year and older

Sex eligibility

All sexes

Study type

Observational

Primary location

Health Sciences University Fatih Sultan Mehmet Training and Research Hospita

Istanbul, 34752, Turkey (Türkiye)

About this study

Obesity and bariatric surgery are associated with physiological changes that may influence intracranial pressure. Pneumoperitoneum and reverse Trendelenburg positioning, commonly used during laparoscopic bariatric surgery, can affect venous return, respiratory mechanics, and cerebral hemodynamics. Ultrasonographic measurement of optic nerve sheath diameter (ONSD) is a noninvasive and reliable method for estimating changes in intracranial pressure.

The aim of this prospective clinical study was to investigate the effects of anesthesia induction, pneumoperitoneum, and patient positioning on intracranial pressure in patients undergoing bariatric surgery. ONSD measurements were obtained at five predefined time points: before anesthesia induction in the supine position (T0), 5 minutes after anesthesia induction (T1), 5 minutes after creation of pneumoperitoneum and placement in the reverse Trendelenburg position (T2), at the 20th minute of pneumoperitoneum (T3), and 5 minutes after termination of pneumoperitoneum and return to the supine position (T4).

Hemodynamic parameters, end-tidal carbon dioxide levels, peak airway pressure, and plateau airway pressure were recorded simultaneously. The primary outcome was the change in ONSD measurements during different stages of the surgical procedure. The study sought to determine whether pneumoperitoneum and patient positioning contribute to changes in intracranial pressure during bariatric surgery.

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Patients scheduled for bariatric surgery.
  • ASA physical status 1-3
  • Patients aged 18 years and older

Exclusion criteria

  • Patients who declined to participate.
  • Age <18 years.
  • ASA physical status IV.
  • Previous cataract surgery.
  • Presence of conditions associated with increased intracranial pressure, including hydrocephalus, cerebrovascular disease, or intracranial tumors.
  • Ocular conditions that could interfere with optic nerve sheath diameter measurement, including globe pathology or glaucoma

Treatment and study plan

Optic Nerve Sheath Diameter Measurement

Diagnostic Test

Ultrasonographic measurement of optic nerve sheath diameter (ONSD) performed at predefined perioperative time points to assess changes in intracranial pressure during bariatric surgery.

Primary outcomes

  1. Optic Nerve Sheath Diameter (ONSD) at T0

    Time frame: within 5 minutes before induction of anesthesia (T0)

    ONSD was measured by ultrasonography before induction of anesthesia ,with the patient awake and in the supin position.ONSD was recorded in millimeters(mm)

  2. optic nerve sheath diameter (ONSD) T1

    Time frame: 5 minutes after induction of anesthesia (T1)

    ONSD measured by ultrasonography 5 minutes after induction of anesthesia ,with the patient in the supin position.ONSD will be reported in millimeters(mm)

  3. Optic Nerve Sheath Diameter (ONSD) at T2

    Time frame: 5 minutes after pneumoperitoneum and reverse Trendelenburg positioning (T2)

    ONSD measured by ultrasonography 5 minutes after pneumoperitoneum and positioning in reverse Trendelenburg. ONSD will be reported in millimeters (mm).

  4. Optic Nerve Sheath Diameter (ONSD) at T3

    Time frame: 20 minutes after establishment of pneumoperitoneum in the reverse trendelenburg position (T3)

    ONSD measured by ultrasonography 20 minutes after pneumoperitoneum while maintaining the reverse Trendelenburg position. ONSD will be reported in millimeters (mm).

  5. Optic Nerve Sheath Diameter (ONSD) at T4

    Time frame: 5 minutes after termination of pneumoperitoneum and return to the supine position (T4)

    ONSD measured by ultrasonography 5 minutes after termination of pneumoperitoneum and return to the supine position. ONSD will be reported in millimeters (mm).

Secondary outcomes

  1. changes in hemodynamic and respiratory parameters

    Time frame: from within 5 minutes before induction of anesthesia (T0) to 5 minutes after termination of pneumoperitoneum and return to the supine position (T4).

    Hemodynamic and respiratory parameters, including systolic, diastolic and mean arterial blood pressure, heart rate, peripheral oxygen saturation (SpO₂), end-tidal carbon dioxide (EtCO₂), peak airway pressure (Ppeak), and plateau airway pressure (Pplateau), were recorded at predefined perioperative time points and evaluated in relation to changes in optic nerve sheath diameter (ONSD).

Sponsors and collaborators

Lead sponsor

Fatih Sultan Mehmet Training and Research Hospital

Other

Registry information

Official study title

Evaluation of Optic Nerve Sheath Diameter Changes During Laparoscopic Bariatric Surgery Performed in Reverse Trendelenburg Position

Important dates

Study start
2022
Primary completion
2024
Study completion
2024
First posted
Jun 23, 2026
Registry last updated
Sep 10, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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