Stone Retropulsion with Ho: YAG and Tm: YAG Lasers: A Clinical Practice-Oriented Experimental Study.

OBJECTIVE: To compare the retropulsion of stones with the use of holmium: yttrium aluminum garnet (Ho: YAG) laser and thulium: yttrium aluminum garnet (Tm: YAG) laser in settings that could be used in clinical practice. METHODS: The experimental configuration included a glass tube set in a water bath filled with physiologic saline. Plaster of Paris stones were inserted in the tube. Tm: YAG and Ho: YAG laser systems were used along with a high-speed slow-motion camera. The lasers were activated with different settings. The displacement of the stone was measured according to a custom-made algorithm. RESULTS: Ho: YAG: the retropulsion of stones was the lowest with the energy setting of 0.5 J and the frequency of 20 Hz with long pulse duration. The highest retropulsion was observed in the case of 3 J, 5 Hz, and short pulse. Tm: YAG: the retropulsion of stones was the lowest with the energy setting of 1 J and the frequency of 10 Hz with either long or short pulse duration. Practically, there was no retropulsion at all. The highest retropulsion was observed in the case of 8 J, 5 Hz, and short pulse. CONCLUSION: Ho: YAG laser has a linear increase in stone retropulsion with increased pulse energy. On the other hand, the retropulsion rate was kept to the minimum with Tm: YAG as much as the energy level of 8 J. The activation of lasers with short pulse resulted in further displacement of the stone. Lower frequency with the same power setting seemed to result in further stone retropulsion. Higher power with the same frequency setting resulted in further displacement of the stone.

Thulium Laser in the Upper Urinary Tract: Does the Heat Generation in the Irrigation Fluid Pose a Risk? Evidence from an In Vivo Experimental Study.

INTRODUCTION: The current experimental study aimed at evaluating the temperature raise of the irrigation fluid caused by the use of the thulium (Tm:YAG) and holmium laser (Ho:YAG) in the upper urinary tract (UT) of pigs. MATERIALS AND METHODS: An experimental setting was designed for the investigation of differences in the temperature of the irrigation fluid in the renal pelvis of a porcine model under different flow rates and laser power settings. The experimental configuration included a single-use flexible ureteroscope, a Tm:YAG and a Ho:YAG laser system. A thermocouple was inserted through a 6F ureteral catheter that was placed parallel to the FlexVue in the renal pelvis. An additional thermocouple was placed next to the renal pelvis after open preparation of the kidney. Irrigation was achieved with either the irrigation bags placed 1 m above the level of the pig or with the use of an irrigation pump (30 and 60 compressions per minute). RESULTS: Tm:YAG (10, 20, 30, 40 W): The higher flow provided by the pump system minimized the increase of temperature within the renal pelvis regardless of the laser power. The external temperature increase was lower in comparison to the increase inside the renal pelvis. The internal temperature could increase up to 10.5°C from a baseline value of 23°C. Ho:YAG (10, 20 W): There was no temperature change or an increase of only 2.1°C under the different power and irrigation flow rate settings. There were no differences in the temperature between the inside and outside of the renal pelvis. CONCLUSION: The use of Tm:YAG in continuous mode with power settings up to 40 W and flow rates similar to those used in the clinical practice seemed to result in temperature increases in the irrigation fluid, which do not represent a risk for the renal tissue during the UT endoscopic surgery.

Does the Heat Generation by the Thulium:Yttrium Aluminum Garnet Laser in the Irrigation Fluid Allow Its Use on the Upper Urinary Tract? An Experimental Study.

INTRODUCTION: The current experimental study aimed into evaluating the temperature raise of the irrigation fluid caused by the use of the Thulium:Yttrium aluminum garnet (Tm:YAG) laser. The study setting was designed to replicate conditions of upper urinary tract (UT) surgery. MATERIALS AND METHODS: An experimental setting was designed for the investigation of differences in the temperature of the irrigation fluid in different flow rates, laser power settings, and laser activation times and modes. The experimental configuration included a burette equipped with a micrometric stopcock, a thermocouple, and a modified 40-mL vessel. A Tm:YAG and Holmium:Yttrium aluminum garnet (Ho:YAG) laser devices were used. RESULTS: The Tm:YAG in the continuous mode and in power settings of 5, 10, and 20 W showed similar temperature changes during the 10-minute observation period. The temperatures of the Tm:YAG in the pulsed mode tended to range within similar levels (46.8°C-61°C) with the continuous mode (47.8°C-68°C) when power settings up to 20 W were considered. When the higher power settings (50 and 100 W) were investigated, the temperatures reached were significantly higher in both pulsed and continuous modes. The Ho:YAG showed similar temperatures in comparison to the Tm:YAG in all the flow rates and power settings. The temperatures ranged between 45.6°C and 68.7°C. CONCLUSION: The Tm:YAG in the pulsed and continuous mode with power settings up to 20 W seemed to have potential for UT use. By combining a power setting at the above limit and a low flow rate (as low as 2 mL/minute), it is possible to use the Tm:YAG with safety in terms of temperature.