Normal vs Low Tidal Volume Ventilation in Retrograde Intrarenal Surgery - A Randomized Controlled Trial

Comparison of Normal Ventilation and Low Tidal Volume Ventilation During Retrograde Intrarenal Surgery (RIRS) Using Video-Based Motion Index: A Randomized Controlled Trial

Retrograde intrarenal surgery is commonly performed under general anesthesia for the treatment of renal stones. During the procedure, respiratory-related renal movement caused by positive-pressure ventilation may impair endoscopic image stability and reduce the efficiency of laser lithotripsy. This randomized controlled trial aims to compare the effects of normal ventilation and low tidal volume ventilation on intraoperative endoscopic image stability during RIRS using a video-based Motion Index.

Eligible adult patients scheduled for elective RIRS under general anesthesia will be randomized in a 1:1 ratio to either normal tidal volume ventilation or low tidal volume ventilation. A standardized 60-second intraoperative video segment in which the stone and/or active laser lithotripsy is visible will be analyzed by blinded assessors. The primary outcome is the mean Motion Index value calculated from sequential video frames. Secondary outcomes include additional Motion Index parameters, laser activation time, anesthesia and surgical duration, intraoperative respiratory and hemodynamic safety parameters, vasopressor requirement, complications, and stone-free status at routine follow-up.

Study Overview

• Status: Recruiting
• Conditions: Renal Calculi
• Intervention / Treatment: Procedure: low tidal volume ventilation

Detailed Description

Retrograde intrarenal surgery (RIRS) is a minimally invasive endourological procedure widely used for the treatment of renal stones. Because the procedure is performed within the narrow collecting system of the kidney, endoscopic image stability is important for accurate laser targeting, efficient lithotripsy, and procedural safety. During general anesthesia, positive-pressure ventilation may cause diaphragmatic and respiratory-related renal movement, resulting in micro-movements of the endoscopic image. These movements may interfere with continuous laser targeting and may reduce procedural efficiency.

This study is designed as a single-center, prospective, randomized, parallel-group, assessor-blinded controlled trial. Adult patients scheduled for elective RIRS under general anesthesia will be enrolled after obtaining written informed consent. Participants will be randomized in a 1:1 ratio to one of two intraoperative ventilation strategies: normal tidal volume ventilation or low tidal volume ventilation. Randomization will be performed using a computer-generated randomization list, and allocation concealment will be ensured with sequentially numbered, opaque, sealed envelopes. The video assessors will be blinded to group allocation.

After induction of general anesthesia and endotracheal intubation, mechanical ventilation will be standardized according to the assigned group. In the normal ventilation group, tidal volume will be set at 6-8 mL/kg predicted body weight with 5 cmH₂O PEEP. In the low tidal volume ventilation group, tidal volume will be set at 4-6 mL/kg predicted body weight with 5 cmH₂O PEEP. In both groups, respiratory rate will be titrated to maintain EtCO₂ within the target range of 35-45 mmHg, and FiO₂ will be adjusted to maintain SpO₂ above 94%. Patient safety will take priority throughout the study, and ventilation settings may be modified if clinically required. Any protocol deviations will be recorded.

Intraoperative endoscopic videos obtained during routine RIRS will be used for the video-based analysis. After the procedure, video files will be anonymized and coded in a way that does not reveal group allocation. A standardized 60-second segment in which the stone is clearly visible and/or laser lithotripsy is active will be selected according to predefined criteria. The selected segments will be analyzed using a phase-correlation-based image registration method. Sequential video frames will be converted to grayscale, mild noise reduction will be applied, and horizontal and vertical image displacement between consecutive frames will be calculated. The Motion Index will be derived from these displacement components for each frame pair, generating a time series for each patient.

The primary outcome of the study is the mean Motion Index value calculated from the standardized intraoperative video segment. Secondary outcomes include additional Motion Index parameters, including median, 95th percentile, and maximum Motion Index values; laser activation time; anesthesia duration; surgical duration; intraoperative respiratory and hemodynamic parameters such as EtCO₂, SpO₂, mean arterial pressure, heart rate, airway pressures when available, and vasopressor requirement; perioperative complications; and stone-free status at routine postoperative follow-up, planned at approximately 4 weeks.

The study aims to determine whether low tidal volume ventilation improves endoscopic image stability during RIRS without compromising respiratory or hemodynamic safety. The findings may contribute to the standardization of anesthetic ventilation strategies during endourological stone surgery and may provide an objective, reproducible method for evaluating respiratory-related image motion during RIRS.

• Study Type: Interventional
• Enrollment (Estimated): 60
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Sibel Onen Ozdemir, MD; Phone Number: +905442892194; Email: sibelonen89@gmail.com

Study Locations

• Turkey (Türkiye)
  • Çorum, Turkey (Türkiye)
    • Recruiting
    • Hitit university
    • Contact: Ozgur Yagan, Professor

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Adult patients aged 18 years or older
• Patients scheduled for elective retrograde intrarenal surgery under general anesthesia
• ASA physical status I-III
• Patients who are able to read and understand the informed consent form
• Patients who provide written informed consent

Exclusion Criteria:

• Patients younger than 18 years
• Pregnancy
• Emergency surgery
• Severe chronic obstructive pulmonary disease, severe restrictive pulmonary disease, or preoperative hypercapnia
• Severe uncontrolled cardiovascular disease
• Active urinary tract infection, sepsis, or untreated infectious focus
• Cases in whom the standardized ventilation protocol is difficult to apply because of morbid obesity
• Patients scheduled for an additional major urological procedure in the same session
• Cases in which an intraoperative video recording of sufficient quality cannot be obtained
• Patients in whom the study protocol cannot be safely continued according to the investigator's clinical judgment

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Single

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: Normal Tidal Volume Ventilation; Participants in this group will receive standard mechanical ventilation after induction of general anesthesia and endotracheal intubation during retrograde intrarenal surgery. Tidal volume will be set at 6-8 mL/kg predicted body weight with 5 cmH₂O PEEP. Respiratory rate will be titrated to maintain EtCO₂ between 35 and 45 mmHg, and FiO₂ will be adjusted to maintain SpO₂ above 94%.	Procedure: low tidal volume ventilation; Participants allocated to the normal tidal volume ventilation group will receive volume-controlled mechanical ventilation during retrograde intrarenal surgery under general anesthesia. Tidal volume will be set at 6-8 mL/kg predicted body weight with 5 cmH₂O PEEP. Respiratory rate will be titrated to maintain EtCO₂ between 35 and 45 mmHg, and FiO₂ will be adjusted to maintain SpO₂ above 94%.; Other Names: Normal Tidal Volume Ventilation
Experimental: Low Tidal Volume Ventilation; Participants in this group will receive low tidal volume mechanical ventilation after induction of general anesthesia and endotracheal intubation during retrograde intrarenal surgery. Tidal volume will be set at 4-6 mL/kg predicted body weight with 5 cmH₂O PEEP. Respiratory rate will be titrated to maintain EtCO₂ between 35 and 45 mmHg, and FiO₂ will be adjusted to maintain SpO₂ above 94%.	Procedure: low tidal volume ventilation; Participants allocated to the normal tidal volume ventilation group will receive volume-controlled mechanical ventilation during retrograde intrarenal surgery under general anesthesia. Tidal volume will be set at 6-8 mL/kg predicted body weight with 5 cmH₂O PEEP. Respiratory rate will be titrated to maintain EtCO₂ between 35 and 45 mmHg, and FiO₂ will be adjusted to maintain SpO₂ above 94%.; Other Names: Normal Tidal Volume Ventilation

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Mean Motion Index During Retrograde Intrarenal Surgery	Mean Motion Index will be calculated from a standardized 60-second intraoperative endoscopic video segment in which the stone is clearly visible and/or laser lithotripsy is active. Consecutive video frames will be analyzed using a phase-correlation-based image registration method. Horizontal and vertical displacement components between consecutive frames will be used to generate the Motion Index time series, and the mean value will be used as the primary measure of endoscopic image motion.	Intraoperative period, during a standardized 60-second video segment

Collaborators and Investigators

• Sponsor: Hitit University

Study record dates

Study Major Dates

• Study Start (Actual): April 29, 2026
• Primary Completion (Estimated): August 15, 2026
• Study Completion (Estimated): September 1, 2026

Study Registration Dates

• First Submitted: June 8, 2026
• First Submitted That Met QC Criteria: June 8, 2026
• First Posted (Actual): June 11, 2026

Study Record Updates

• Last Update Posted (Actual): June 11, 2026
• Last Update Submitted That Met QC Criteria: June 8, 2026
• Last Verified: June 1, 2026

More Information

Terms related to this study

• Keywords: Retrograde intrarenal surgery , Low tidal volume ventilation, General anesthesia, Stone free, Video-based image analysis
• Additional Relevant MeSH Terms: Urogenital Diseases; Male Urogenital Diseases; Calculi; Pathological Conditions, Anatomical; Kidney Diseases; Urologic Diseases; Female Urogenital Diseases; Female Urogenital Diseases and Pregnancy Complications; Urolithiasis; Urinary Calculi; Nephrolithiasis; Pathological Conditions, Signs and Symptoms; Kidney Calculi
• Other Study ID Numbers: 2026-17

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: Individual participant data will not be publicly shared due to privacy, confidentiality, and institutional ethical restrictions. De-identified data may be made available from the principal investigator upon reasonable request and with appropriate institutional permission.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No