Caveat Emptor: The Heat Is "ON": An In Vivo Evaluation of the Thulium Fiber Laser and Temperature Changes in the Porcine Kidney during Dusting and Fragmentation Modes.

INTRODUCTION We sought to examine the intrarenal fluid and tissue temperature during dusting and fragmentation with the Thulium fiber laser (TFL) in an in vivo porcine kidney. METHODS In two pigs, temperature was continuously measured within the upper, middle, and lower calyces and at the tip of the ureteroscope. Four experimental protocols were performed: dual lumen ureteroscope with both warmed (37°C) and room temperature (20-22oC) irrigation and single lumen ureteroscope with warmed and room temperature irrigation. In each pig, one kidney had a 14F ureteral access sheath (UAS), other kidney had no UAS. A 200µm TFL was fired at three settings: dusting (0.5J, 80Hz, 40W) with continuous activation for 5 minutes or until a temperature reached 44⁰C; low power (1J, 10Hz, 10W) and high-power fragmentation (1.5J, 20Hz, 30W). For fragmentation, the laser was activated for 10 seconds with a 2 second intermission for 1 minute. RESULTS In the absence of an UAS, in all but one circumstance, temperatures exceeded 44oC at all settings with the use of either warm or room temperature irrigation, regardless of the type of ureteroscope. Temperatures recorded at the ureteroscope tip were 4oC - 22oC less than the temperatures recorded in the renal calyces. In contrast, with a 14F UAS in place, 6 distinct groups had temperatures that did not exceed 44oC, specifically at low and high-power fragmentation settings with room temperature irrigation for both sets of ureteroscopes and at dusting and low-power fragmentation settings with warm temperature irrigation solely for the single lumen ureteroscope. Temperatures at the ureteroscope tip with an UAS yielded temperature differences from 17oC less to 19oC more than the renal calyces. CONCLUSIONS Thulium fiber laser is a novel technology for lithotripsy. In the absence of a UAS, high-power TFL fragmentation settings, may create temperatures that could result in urothelial tissue injury.