Morbid ObesityONSDNCT07639502
Impact of Reverse Trendelenburg on ONSD in Obesity Surgery
A study testing Pre-pneumoperitoneum Reverse Trendelenburg Group in people with Morbid Obesity, run by Bagcilar Training and Research Hospital at 1 site in Turkey (Türkiye).
Trial summary
This prospective randomized controlled trial aims to investigate the effect of reverse Trendelenburg positioning applied before pneumoperitoneum on optic nerve sheath diameter (ONSD) and, consequently, intracranial pressure during laparoscopic bariatric surgery. Read more about this study
- Who is it for?
- Ages 18 to 65 yearsHealthy volunteers can take part
- Conditions the study is for
- Morbid Obesity
- What is being tested?
- Pre-pneumoperitoneum Reverse Trendelenburg Group
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 90 participants
- Where
- 1 siteTurkey (Türkiye)
- Study dates
- 1 Jan 2026to 1 Jun 2026
- Phase
- Interventional
- 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
- Healthy volunteers accepted
- Adult, Older adult
Who may be able to join
- Age between 18 and 65 years.
- American Society of Anesthesiologists (ASA) physical status I-III.
- Body mass index (BMI) ≥ 40 kg/m² and scheduled for elective laparoscopic bariatric surgery.
- Ability to provide written informed consent.
- Willingness to participate in the study and comply with study procedures.
Who cannot join
- Age younger than 18 years or older than 65 years.
- Refusal or inability to provide written informed consent.
- History of ophthalmologic disease that may affect optic nerve sheath diameter (ONSD) measurements (e.g., glaucoma, optic neuritis, optic nerve tumors, severe ocular trauma, previous ocular surgery).
- Known intracranial pathology, including intracranial hypertension, hydrocephalus, intracranial mass lesions, or cerebrovascular disease.
- Neurological disorders that may influence intracranial pressure measurements.
- Emergency surgery.
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- Pregnancy.
- Severe cardiopulmonary disease (e.g., decompensated heart failure, severe pulmonary hypertension, severe chronic obstructive pulmonary disease).
- Inability to obtain adequate ocular ultrasonography images for ONSD measurement.
- Conversion from laparoscopic to open surgery. Intraoperative events requiring deviation from the study protocol.
Trial locations and contacts
1 site in 1 country.
About this study
Official title: Effect of Pre-pneumoperitoneum Reverse Trendelenburg Positioning on Optic Nerve Sheath Diameter During Bariatric Surgery: A Prospective Randomized Controlled Trial
This prospective randomized controlled trial aims to investigate the effect of reverse Trendelenburg positioning applied before pneumoperitoneum on optic nerve sheath diameter (ONSD) and, consequently, intracranial pressure during laparoscopic bariatric surgery. Patients will be randomly assigned to two groups, and perioperative changes in ONSD will be compared between the groups. The primary hypothesis of the study is that applying the reverse Trendelenburg position before pneumoperitoneum may attenuate ONSD enlargement and thereby help prevent increases in intracranial pressure.
Read the detailed description
Obesity is associated with physiological alterations that may affect intracranial dynamics during laparoscopic surgery. In bariatric procedures, the creation of pneumoperitoneum and the use of reverse Trendelenburg positioning are essential for optimal surgical exposure. However, pneumoperitoneum increases intra-abdominal pressure and may impair venous return from the brain, potentially leading to elevations in intracranial pressure (ICP). These effects may be particularly relevant in obese patients, who are more susceptible to hemodynamic and respiratory changes during surgery.
Direct measurement of ICP using intraventricular or intraparenchymal catheters remains the gold standard; however, these invasive techniques are not feasible in routine surgical practice because of the risks of hemorrhage, infection, and other complications. Ultrasonographic measurement of optic nerve sheath diameter (ONSD) has emerged as a reliable, noninvasive surrogate marker for assessing changes in ICP and has been widely used in perioperative and critical care settings.
Previous studies have demonstrated that pneumoperitoneum may increase ONSD during laparoscopic procedures. Reverse Trendelenburg positioning has been shown to facilitate cerebral venous drainage and may attenuate increases in intracranial pressure. However, the effect of the timing of reverse Trendelenburg positioning relative to pneumoperitoneum creation has not been adequately investigated, particularly in patients undergoing bariatric surgery.
This prospective randomized controlled trial aims to evaluate whether applying the reverse Trendelenburg position before pneumoperitoneum can reduce perioperative increases in ONSD during laparoscopic bariatric surgery. Eligible patients undergoing elective laparoscopic bariatric surgery will be randomly assigned to one of two groups. In the conventional group, pneumoperitoneum will be established before reverse Trendelenburg positioning. In the intervention group, reverse Trendelenburg positioning will be applied before pneumoperitoneum creation.
ONSD measurements will be performed using ocular ultrasonography at predefined perioperative time points. Hemodynamic parameters, including mean arterial pressure and heart rate, as well as respiratory variables including end-tidal carbon dioxide and peak airway pressure, will also be recorded.
- Conditions
- Morbid Obesity
- Being tested
- Pre-pneumoperitoneum Reverse Trendelenburg Group
- Keywords
- Morbid Obesity, Optic Nerve Sheath Diameter (ONSD), Bariatric Surgery, Reverse Trendelenburg Positioning
- Medical subject headings
- Obesity, Morbid
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Pre-pneumoperitoneum Reverse Trendelenburg GroupOther
Patients are placed in the reverse Trendelenburg position before carbon dioxide insufflation and establishment of pneumoperitoneum.
| Study group | Role | What they receive |
|---|---|---|
| Pre-pneumoperitoneum Reverse Trendelenburg Group | Active comparator | Reverse Trendelenburg positioning is applied before pneumoperitoneum creation. Receives: Other: Pre-pneumoperitoneum Reverse Trendelenburg Group |
| Conventional Positioning Group | No intervention | Pneumoperitoneum is established in the supine position before reverse Trendelenburg positioning. |
What is being measured
The primary outcome is the main question the study is designed to answer.
Change in Optic Nerve Sheath Diameter (ONSD)
Optic nerve sheath diameter will be measured ultrasonographically at predefined perioperative time points. The outcome measure is the change in ONSD from baseline and the difference between study groups.
Measured: Baseline (before induction of anesthesia), immediately after induction, 5 minutes after pneumoperitoneum and positioning, and at the end of surgery.
Secondary outcomes (3)
Mean Arterial Pressure (MAP)
Mean arterial pressure measured during surgery
Measured: During the intraoperative period
Heart Rate
Heart rate measured during surgery.
Measured: During the intraoperative period
Peak Airway Pressure
Peak airway pressure measured during surgery
Measured: During the intraoperative period
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted10 Jun 2026
- Study start1 Jan 2026
- Primary completion15 Apr 2026
- Study completion1 Jun 2026
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Morbid ObesityStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Other
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Model description
- Participants will be randomly assigned to one of two parallel groups. In the conventional group, pneumoperitoneum will be established in the supine position, followed by placement in the reverse Trendelenburg position. In the intervention group, patients will first be placed in the reverse Trendelenburg position before pneumoperitoneum creation. Perioperative optic nerve sheath diameter (ONSD), hemodynamic variables, respiratory parameters, and postoperative outcomes will be compared between the two groups to evaluate the effect of pre-pneumoperitoneum reverse Trendelenburg positioning on intracranial pressure during laparoscopic bariatric surgery.
- Masking
- None (open label)
- Enrolment
- 90 participants (actual)
Sponsor and investigators
- Lead sponsor
- Bagcilar Training and Research Hospital
- Sponsor type
- Other government
- Responsible party
- Principal investigator, Sezen Kumaş Solak, Bagcilar Training and Research Hospital
- Investigators
- SEZEN KUMAS SOLAK, MD, Study director, Bagcılar Training Research Hospital
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07639502
- Sponsor's protocol ID
- BAGCILAR obezite
- Acronym
- ONSD
- Status last verified
- Jul 2026
- First submitted
- 1 Jun 2026
- Last updated
- 14 Jul 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 14 Jul 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Effect of Pre-pneumoperitoneum Reverse Trendelenburg Positioning on Optic Nerve Sheath Diameter During Bariatric Surgery: A Prospective Randomized Controlled Trial
- ClinicalTrials.gov ID
- NCT07639502
- Acronym / sponsor ID
- ONSD / BAGCILAR obezite
- Conditions
- Morbid Obesity
- Keywords
- Morbid Obesity, Optic Nerve Sheath Diameter (ONSD), Bariatric Surgery, Reverse Trendelenburg Positioning
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 90 participants (actual)
- Lead sponsor
- Bagcilar Training and Research HospitalOther government
- Study start
- 1 Jan 2026 (actual)
- Primary completion
- 15 Apr 2026 (actual)
- Study completion
- 1 Jun 2026 (actual)
- First posted
- 10 Jun 2026 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
This prospective randomized controlled trial aims to investigate the effect of reverse Trendelenburg positioning applied before pneumoperitoneum on optic nerve sheath diameter (ONSD) and, consequently, intracranial pressure during laparoscopic bariatric surgery. Patients will be randomly assigned to two groups, and perioperative changes in ONSD will be compared between the groups. The primary hypothesis of the study is that applying the reverse Trendelenburg position before pneumoperitoneum may attenuate ONSD enlargement and thereby help prevent increases in intracranial pressure.
Detailed description
Obesity is associated with physiological alterations that may affect intracranial dynamics during laparoscopic surgery. In bariatric procedures, the creation of pneumoperitoneum and the use of reverse Trendelenburg positioning are essential for optimal surgical exposure. However, pneumoperitoneum increases intra-abdominal pressure and may impair venous return from the brain, potentially leading to elevations in intracranial pressure (ICP). These effects may be particularly relevant in obese patients, who are more susceptible to hemodynamic and respiratory changes during surgery.
Direct measurement of ICP using intraventricular or intraparenchymal catheters remains the gold standard; however, these invasive techniques are not feasible in routine surgical practice because of the risks of hemorrhage, infection, and other complications. Ultrasonographic measurement of optic nerve sheath diameter (ONSD) has emerged as a reliable, noninvasive surrogate marker for assessing changes in ICP and has been widely used in perioperative and critical care settings.
Previous studies have demonstrated that pneumoperitoneum may increase ONSD during laparoscopic procedures. Reverse Trendelenburg positioning has been shown to facilitate cerebral venous drainage and may attenuate increases in intracranial pressure. However, the effect of the timing of reverse Trendelenburg positioning relative to pneumoperitoneum creation has not been adequately investigated, particularly in patients undergoing bariatric surgery.
This prospective randomized controlled trial aims to evaluate whether applying the reverse Trendelenburg position before pneumoperitoneum can reduce perioperative increases in ONSD during laparoscopic bariatric surgery. Eligible patients undergoing elective laparoscopic bariatric surgery will be randomly assigned to one of two groups. In the conventional group, pneumoperitoneum will be established before reverse Trendelenburg positioning. In the intervention group, reverse Trendelenburg positioning will be applied before pneumoperitoneum creation.
ONSD measurements will be performed using ocular ultrasonography at predefined perioperative time points. Hemodynamic parameters, including mean arterial pressure and heart rate, as well as respiratory variables including end-tidal carbon dioxide and peak airway pressure, will also be recorded.
Study design
- Primary purpose
- Other
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- None (open label)
- Number of arms
- 2
- Model description
- Participants will be randomly assigned to one of two parallel groups. In the conventional group, pneumoperitoneum will be established in the supine position, followed by placement in the reverse Trendelenburg position. In the intervention group, patients will first be placed in the reverse Trendelenburg position before pneumoperitoneum creation. Perioperative optic nerve sheath diameter (ONSD), hemodynamic variables, respiratory parameters, and postoperative outcomes will be compared between the two groups to evaluate the effect of pre-pneumoperitoneum reverse Trendelenburg positioning on intracranial pressure during laparoscopic bariatric surgery.
| Arm | Type | Receives |
|---|---|---|
| Pre-pneumoperitoneum Reverse Trendelenburg Group | Active comparator | Other: Pre-pneumoperitoneum Reverse Trendelenburg GroupReverse Trendelenburg positioning is applied before pneumoperitoneum creation. |
| Conventional Positioning Group | No intervention | –Pneumoperitoneum is established in the supine position before reverse Trendelenburg positioning. |
Who may qualify
- Ages
- 18 to 65 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (5 listed)
- Age between 18 and 65 years.
- American Society of Anesthesiologists (ASA) physical status I-III.
- Body mass index (BMI) ≥ 40 kg/m² and scheduled for elective laparoscopic bariatric surgery.
- Ability to provide written informed consent.
- Willingness to participate in the study and comply with study procedures.
Key exclusion criteria (10 listed)
- Age younger than 18 years or older than 65 years.
- Refusal or inability to provide written informed consent.
- History of ophthalmologic disease that may affect optic nerve sheath diameter (ONSD) measurements (e.g., glaucoma, optic neuritis, optic nerve tumors, severe ocular trauma, previous ocular surgery).
- Known intracranial pathology, including intracranial hypertension, hydrocephalus, intracranial mass lesions, or cerebrovascular disease.
- Neurological disorders that may influence intracranial pressure measurements.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Pre-pneumoperitoneum Reverse Trendelenburg GroupPatients are placed in the reverse Trendelenburg position before carbon dioxide insufflation and establishment of pneumoperitoneum. | Other | Pre-pneumoperitoneum Reverse Trendelenburg Group |
Primary outcome
Change in Optic Nerve Sheath Diameter (ONSD)
Time frame: Baseline (before induction of anesthesia), immediately after induction, 5 minutes after pneumoperitoneum and positioning, and at the end of surgery.
Optic nerve sheath diameter will be measured ultrasonographically at predefined perioperative time points. The outcome measure is the change in ONSD from baseline and the difference between study groups.
3 secondary outcomes
Mean Arterial Pressure (MAP)
Time frame: During the intraoperative period
Heart Rate
Time frame: During the intraoperative period
Peak Airway Pressure
Time frame: During the intraoperative period
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 14 Jul 2026.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
SEZEN KUMAS SOLAK, MD study director
Bagcılar Training Research Hospital
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Pre-pneumoperitoneum Reverse Trendelenburg Group in people with Morbid Obesity, run by Bagcilar 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 5 inclusion and 10 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 14 Jul 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?
Change in Optic Nerve Sheath Diameter (ONSD) (time frame: Baseline (before induction of anesthesia), immediately after induction, 5 minutes after pneumoperitoneum and positioning, and at the end of surgery.). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
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 14 Jul 2026.