Power is not performance: Analysis of laser‐use metrics from a randomised clinical trial comparing low‐ and high‐power ureteroscopic lithotripsy

Objective Thulium fibre laser (TFL) offers a wide range of power settings during ureteroscopic (URS) lithotripsy, yet the impact of power selection on intraoperative laser‐use dynamics remains unclear. The objective of this study was to characterise differences in laser activation patterns between low‐power (LP) and high‐power (HP) TFL during sheathless URS. Materials and Methods This was a predefined secondary analysis of intraoperative laser data collected during a randomised clinical trial comparing LP (0.4–0.6 J × 10 Hz; 4–6 W) and HP (0.4–0.8 J × 20–40 Hz; 16–18 W) TFL URS lithotripsy. Flexible URS was performed without a ureteral access sheath. Laser system logs provided time‐stamped activation and pause events with microsecond precision. Laser‐use dynamics were characterised using a predefined set of complementary metrics, including active laser time (ALT), laser operating time (LOT), total activation count, activation durations, pause durations and operator duty cycle (ODC = ALT/LOT). Group comparisons used Holm–Bonferroni–adjusted p values. Results Data from 72 LP and 74 HP procedures were analysed. ALT was longer with LP (23 vs. 13 min; p < 0.001), whereas LOT was similar (31 vs. 30 min; p = 0.194). LP had a lower activation count (55 vs. 89; p < 0.001) and longer activations (median 24 s vs. 7 s; p < 0.001). Empirical cumulative distribution function analysis showed 89.4% of LP activations lasted ≤30 s compared with 97.2% for HP ( p < 0.001). Total pause time was shorter in LP (8 vs. 14 min; p < 0.001), resulting in a higher ODC (73% vs. 49%; p < 0.001). Conclusion LP and HP TFL lithotripsy result in distinctly different laser‐use dynamics during sheathless URS. LP supported sustained, continuous lasing, whereas HP yielded fragmented activation requiring frequent pauses. Coupled with superior stone‐free outcomes in the parent trial, these findings suggest that preserving clear endoscopic visibility and more active lasing may be more impactful than increasing laser power.