Presentation Authors: Brenton Winship*, Daniel Wollin, Evan Carlos, Chloe Peters, Durham, NC, Jingqiu Li, Singapore, Singapore, Russell Terry, Kohldon Boydston, Glenn Preminger, Michael Lipkin, Durham, NC
Introduction: Temperatures over 43Â°C - the threshold for cellular death - may be achieved during ureteroscopic holmium laser lithotripsy. While prior studies have shown the importance of irrigation during laser activation, the time to reach and subsequently clear dangerous temps across common irrigation pressures has not been studied.
Methods: A flexible ureteroscope (Lithovue) or a short Olympus semirigid (SR) ureteroscope was placed within a 36cm, 13Fr ureteral access sheath inserted into a full 250cc bag of saline to simulate a normal caliber ureter, renal pelvis reservoir, and antegrade irrigant flow. A thermocouple was placed adjacent to the tip of a 365Âµm laser fiber fired for 45sec at 0.6J/6Hz, 0.8J/8Hz, 1J/10Hz, 1J/20Hz, and 0.2J/80Hz. Two runs per setting at irrigation pressures of 200, 100, and 0mmHg were tested. Mean temp changes were recorded with 6Â°C above baseline as a threshold (as body temp is 6Â° below the 43Â°C mark).
Results: SR group: At 200mmHg there was no mean temp change >6Â°C. At 100mmHg temp changes >6Â° were seen only at 1J/20Hz as quickly as 1sec of activation and returned to â‰¤6Â° within 1sec. At 0mmHg of pressure, temps changes >6Â° were seen at all laser settings and occurred within 1sec when power was â‰¥10W. The 0.2J/80Hz tests were halted early due to boiling. T returned to â‰¤6Â°C within 5sec in all but 0.2J/80Hz, which took 10sec (Fig A-C). _x000D_
Flexible group: At 200mmHg, temp changes >6Â°C occurred with 1J/10Hz (15sec), 0.2J/80Hz (3sec), and 1J/20Hz (2sec). Temps returned to â‰¤6Â° of baseline within 2sec for each setting. At 100mmHg, temp changes >6CÂ° occurred in all but 0.6J/6Hz. Temps returned to â‰¤6Â°C in 10sec at 0.2J/80Hz and 1J/20Hz while .8J/8Hz and 1J/10Hz took 3 and 4sec, respectively. At 0mmHg, all settings produced temp changes >6Â°C within 3sec, except 0.6J/6Hz (35sec). Temps returned to â‰¤6Â°C in 10sec for 1J/10Hz and 0.2J/80Hz and 1sec with 0.6J/6Hz (Fig D-F).
Conclusions: Potentially dangerous intraureteral temperatures were achieved in our in vitro model in as little as 1 second at common irrigation pressures, particularly with a flexible ureteroscope and laser settings â‰¥10W. However, these high temps quickly returned to a safe level within seconds at each irrigation pressure.