Transient apnoea for motion control during flexible ureteroscopic lithotripsy: a randomised trial

Objectives To determine whether transient apnoea (TA) during flexible ureteroscopic laser lithotripsy improves active lithotripsy efficiency compared with regular mechanical ventilation (RMV) and small tidal‐volume ventilation (STVV). Patients and Methods In this single‐centre, three‐arm randomised trial, 150 adults with a single computed tomography (CT)‐confirmed renal, ureteropelvic, or proximal ureteric stone measuring 10–<20 mm were assigned one‐to‐one‐to‐one to RMV, STVV, or TA. TA followed 5‐min 100% oxygen pre‐oxygenation, with 9‐min maximum and pre‐specified stopping criteria under continuous anaesthetic monitoring. The primary endpoint was active lithotripsy efficiency, defined as CT‐estimated stone volume divided by elapsed active lithotripsy time. Analyses followed the intention‐to‐treat principle. Results The mean (standard deviation) active lithotripsy efficiency was 27.8 (8.9), 26.6 (8.0), and 34.3 (10.0) mm 3 /min with RMV, STVV, and TA, respectively ( P < 0.001). TA increased adjusted efficiency by 5.9 mm 3 /min vs RMV (95% confidence interval [CI] 2.2–9.6 mm 3 /min) and 6.8 mm 3 /min vs STVV (95% CI 3.3–10.2 mm 3 /min). The median active lithotripsy time was 27.5, 26.5, and 22.0 min ( P = 0.001); total operative time was 50.0, 50.0, and 43.0 min ( P = 0.002); and surgeon‐rated targeting stability scores were 7.0, 7.0, and 9.0 ( P < 0.001), respectively. Postoperative Day 1/1‐month stone‐free rates were 88%/92%, 80%/96%, and 88%/90%, respectively, with no significant between‐group differences. The median (interquartile range) achieved apnoea duration was 5.0 (4.5–6.8) min; 46/50 resumed ventilation before the 9‐min maximum, most commonly for heart‐rate decline/bradycardia ( n = 27) or blood‐pressure decline/hypotension ( n = 20). No patient had a peripheral oxygen saturation <90% or a Clavien–Dindo Grade ≥III complication; transient hypercapnia and respiratory acidosis improved after ventilation resumed. Conclusion Transient apnoea improved lithotripsy efficiency and shortened operative time compared with RMV and STVV, with higher surgeon‐rated targeting stability. The benefit was primarily intraoperative, without evidence of greater postoperative stone clearance. Protocolised TA may provide a brief intraoperative motion‐control option with pre‐oxygenation, continuous anaesthetic monitoring, and individualised termination.