LAUSR

INTRODUCTION AND OBJECTIVE The novel thulium fiber laser (TFL) has been shown to break stones more rapidly than the holmium:YAG laser (HL). However, some evidence suggests that the TFL generates more heat. The purpose of this study is to compare ureteral temperatures generated by these lasers during ureteroscopic laser lithotripsy in a benchtop model. METHODS A 1-cm BegoStone was manually impacted in the proximal ureter of a 3D printed kidney-ureter model and submerged in 35.5°C saline. Lithotripsy was performed using a 7.6 French flexible ureteroscope and a 200µm laser fiber without a ureteral access sheath. The Dornier 30W HL, Olympus 100W HL, and Olympus 60W TFL were compared. A needle thermocouple to measure temperature was inserted 2 mm from the laser tip. Irrigation was maintained at 35cc/min at room temperature using the Thermedx FluidSmart System. Intraluminal temperature was continuously recorded for 60 seconds of laser activation. 5 trials were performed for each of 4 different power settings: 3.6, 10, 20, and 30 Watts. ANOVA and Mann-Whitney U tests were performed with p<0.05 considered significant. RESULTS Intraureteral fluid temperature increased as laser power settings increased for all lasers (p<0.05). The TFL generated higher average ureteral fluid temperatures than the Dornier and Empower HL at all power settings tested (p<0.001). The maximum temperature for the TFL was higher than the Dornier and Empower HL at all power settings tested (p<0.001), except at 20W with the Empower HL. At 30W, the TFL exceeded 43°C, the threshold for tissue damage. CONCLUSIONS The TFL generated more heat at all settings tested. Supraphysiologic ureteral temperatures may be generated with extended use at high energy settings and low irrigation rates. Understanding the heat generation properties of both lasers could help improve the safety of ureteroscopic laser lithotripsy.