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IRCT20260627069955N1 IRCT 2026-08-01 Shahid Beheshti University of Medical Sciences The effect of positive end-expiratory pressure (PEEP) on optic nerve sheath diameter during laparoscopic cholecystectomy Comparison of BMI-adjusted positive end-expiratory pressure versus zero positive end-expiratory pressure on optic nerve sheath diameter measured by ultrasonography in adults undergoing elective laparoscopic cholecystectomy 2026-09-03 anticipated 50 Recruiting https://irct.ir/trial/91604 interventional Randomization: Randomized, Blinding: Double blinded, Placebo: Not used, Assignment: Parallel, Purpose: Treatment, Randomization description: Patients will be randomized in a 1:1 ratio into either the control group (0 cmH₂O PEEP) or the PEEP group using block randomization with a fixed block size of four. The unit of randomization will be the individual patient. No stratification will be applied. The randomization sequence will be generated by an independent investigator using a computer-based random number generator (IBM SPSS Statistics version 26). The sequence will be created before patient enrollment and will consist of randomly permuted blocks to ensure balanced allocation between the two groups throughout the recruitment period. Allocation concealment will be maintained using sequentially numbered, opaque, sealed envelopes prepared by a researcher not involved in patient recruitment, anesthesia management, outcome assessment, or statistical analysis. Immediately before induction of anesthesia, the attending anesthesiologist will open the next envelope in sequence to determine group assignment. Thus, allocation concealment will be carried out until the moment of assignment, Blinding description: Participants will be blinded to group allocation and will not be informed whether they receive zero PEEP or BMI-adjusted PEEP during mechanical ventilation. The attending anesthesiologist responsible for intraoperative ventilator management cannot be blinded because adjustment of PEEP is required according to the assigned intervention. However, this anesthesiologist will have no role in outcome assessment, data collection, or statistical analysis. The ultrasonographer who performs all optic nerve sheath diameter (ONSD) measurements, the investigators responsible for collecting perioperative data, and the data analyst will remain blinded to treatment allocation throughout the study. Group allocation will be concealed using sequentially numbered, opaque, sealed envelopes prepared by an independent researcher. The envelopes will be opened only after patient enrollment and immediately before the induction of anesthesia. Study data will be be coded before statistical analysis so that the data analyst remains unaware of group assignments until completion of the final analysis. No Data and Safety Monitoring Board (DSMB) is planned because of the small sample size and the low-risk nature of the study. Manuscript preparation will be based on coded data after completion of the analysis. N/A Symptomatic cholelithiasis requiring elective laparoscopic cholecystectomy. Intervention 1: Intervention group: Patients will receive volume controlled mechanical ventilation with positive end expiratory pressure applied 5 minutes after pneumoperitoneum according to body mass index. Patients with body mass index less than 25 kilograms per square meter will receive 5 centimeters of water positive end expiratory pressure, those with body mass index 25 to 30 kilograms per square meter will receive 8 centimeters of water, and those with body mass index greater than 30 kilograms per square meter will receive 10 centimeters of water. Ventilation will be maintained with a tidal volume of 6 milliliters per kilogram of ideal body weight throughout surgery. Intervention 2: Control group: Patients will receive standard volume controlled mechanical ventilation with zero positive end expiratory pressure throughout surgery. Ventilator settings, including tidal volume of 6 milliliters per kilogram of ideal body weight, respiratory rate adjusted to maintain end tidal carbon dioxide between 35 and 40 millimeters of mercury, inspiratory to expiratory ratio of 1 to 2, and inspired oxygen fraction of 0.5, will be identical to the intervention group. No positive end expiratory pressure will be applied. Yes - There is a plan to make this available What will be shared: Data regarding ultrasonography of patients will be available. When: After data collection completion To whom: Other researchers Conditions: Belonging to academic institution Where to obtain: researcher's personal email fmadadi33@gmail.com How to obtain: Requesting by email Comments:
public Firoozeh Madadi
Next to Shahid Beheshti University of Medical Sciences, Shahid A'rabi Street, Yemen Street, Shahid Chamran Highway
Tehran Iran (Islamic Republic of) 1983963113 +98 21 2303 1290 fmadadi33@gmail.com Shahid Beheshti University of Medical Sciences scientific Firoozeh Madadi
Next to Shahid Beheshti University of Medical Sciences, Shahid A'rabi Street, Yemen Street, Shahid Chamran Highway
Tehran Iran (Islamic Republic of) 1983963113 +98 21 2303 1290 fmadadi33@gmail.com Shahid Beheshti University of Medical Sciences Iraq Adults aged 18–65 years. ASA physical status I–III. Scheduled for elective laparoscopic cholecystectomy under general anesthesia. Ability to provide written informed consent. Eligible for volume-controlled mechanical ventilation during surgery. 18 years 65 years Both History of acute or chronic ophthalmic disease (e.g., glaucoma, optic neuritis, retinal disease, previous ocular surgery affecting ONSD measurement). Known cerebrovascular or neurological disease associated with altered intracranial pressure (such as stroke, intracranial tumor, hydrocephalus, traumatic brain injury). Significant respiratory disease (such as COPD, severe asthma, restrictive lung disease) that may influence ventilatory management. Contraindications to laparoscopic surgery or pneumoperitoneum. Inability to obtain adequate ultrasonographic visualization of the optic nerve sheath. Pregnancy. Z90.4 Acquired absence of other specified parts of digestive tract Other Other Intervention group: Patients will receive volume controlled mechanical ventilation with positive end expiratory pressure applied 5 minutes after pneumoperitoneum according to body mass index. Patients with body mass index less than 25 kilograms per square meter will receive 5 centimeters of water positive end expiratory pressure, those with body mass index 25 to 30 kilograms per square meter will receive 8 centimeters of water, and those with body mass index greater than 30 kilograms per square meter will receive 10 centimeters of water. Ventilation will be maintained with a tidal volume of 6 milliliters per kilogram of ideal body weight throughout surgery. Control group: Patients will receive standard volume controlled mechanical ventilation with zero positive end expiratory pressure throughout surgery. Ventilator settings, including tidal volume of 6 milliliters per kilogram of ideal body weight, respiratory rate adjusted to maintain end tidal carbon dioxide between 35 and 40 millimeters of mercury, inspiratory to expiratory ratio of 1 to 2, and inspired oxygen fraction of 0.5, will be identical to the intervention group. No positive end expiratory pressure will be applied. Optic nerve sheath diameter measured by ultrasonography. Timepoint: Before induction of anesthesia, immediately after tracheal intubation, 5 minutes after pneumoperitoneum, 5 minutes after positive end expiratory pressure application, 5 minutes after peritoneal deflation, and 5 minutes after tracheal extubation. Method of measurement: Measurement of optic nerve sheath diameter by orbital ultrasonography using a seven point five megahertz linear ultrasound probe, with measurements obtained from both eyes at three millimeters behind the optic disc. Shahid Beheshti University of Medical Sciences Approved 2026-06-02 Research Ethics Committee of the School of Medicine, Shahid Beheshti University of Medical Sciences Third floor, School of Medicine, next to Taleghani Hospital, Evin, Shahid Chamran Highway Tehran Tehran Iran (Islamic Republic of)