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%.
Study summary
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.
Eligibility
Sex
ALL
Min age
18 Years
Max age
—
Healthy volunteers
No
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
Primary outcome measure(s)
Mean Motion Index During Retrograde Intrarenal Surgery — Intraoperative period, during a standardized 60-second video segment Mean Video-Based 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. The Video-Based Motion Index is a unitless image-motion metric derived from horizontal and vertical frame-to-frame displacement between consecutive video frames using a phase-correlation-based image registration method. The theoretical minimum value is 0, indicating no detected image displacement. There is no predefined fixed maximum value because the value depends on the magnitude of frame-to-frame displacement. Higher values indicate greater endoscopic image motion and worse image stability.
This page summarises publicly available registry data for informational purposes — not medical advice. Eligibility is determined by each study team; patients should discuss participation with their clinician.
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