Power is not performance: Analysis of laser-use metrics from a randomised clinical trial comparing low- and...

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.

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.

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).

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.