In Vitro Comparison of Stone Fragmentation When Using Various Settings with Modern Variable Pulse Holmium Lasers

There are limited data regarding optimal laser and energy settings during stone fragmentation. We assessed effects on fragmentation using a variety of energy and frequency settings with two laser systems.

Artificial stones were created using BegoStone. A clear polyvinylchloride (PVC) tube with an inner diameter of 13 mm was closed at one end with a removable plug to create the in vitro ureteral and caliceal environments. The Lumenis Pulse 120H and the Cook Rhapsody H-30 holmium lasers were studied in the caliceal and ureteral models. A single urologist fragmented each stone to <2 mm. The caliceal studies assessed the time to fragmentation (n = 56). The ureteral studies measured the retropulsion distance of each stone phantom after 5 minutes of laser treatment time using different pulse width settings (n = 15).

Complete treatment of the stone with the 120H required 10.9 minutes at ≥1 J vs 26.9 minutes at <1 J (p < 0.001). The H-30 showed similar results with treatment times of 11.2 minutes at ≥1 J vs 22.8 minutes at <1 J (p < 0.001). There was no significant difference in treatment time when comparing the two lasers using settings of 0.8 J × 8 Hz and 1.5 J × 10 Hz (25.5 minutes vs 24.8 minutes, p = 0.861; and 13.2 minutes vs 9.5 minutes, p = 0.061; respectively). Retropulsion distances using the 120H were 13.9 cm using long pulse, 25.2 cm using medium pulse, and 56.6 cm using short pulse. Retropulsion distances using the H-30 laser were 7 cm using long pulse and 14.5 cm using short pulse, which differed from the 120H (p < 0.001).

Laser fragmentation was faster with both lasers when energy settings of ≥1 J were used. Treatment times using the 120H and the H-30 lasers were equivalent. Retropulsion distances were less with both lasers when longer pulse widths were used. The H-30 resulted in less stone retropulsion compared with the 120H.