The effect of prolonged laser activation on irrigation fluid temperature: an in vitro experimental study.

PURPOSE: To investigate the effect of prolonged laser activation on irrigation fluid temperature by varying the power settings flow rate (10-30 ml/min). MATERIALS AND METHODS: An experimental study using a 20 ml syringe, 12/14 ureteral access sheath, a dual-lumen catheter and a thermocouple was performed. The laser was fired with 12 W (0.3 J × 40 Hz), 40 W (1 J × 40 Hz), 60 W (1.5 J × 40 Hz) using Quanta Ho 150 W (Quanta System, Samarate, Italy). All trials were performed with fluid outflow rate of 10, 20 and 30 ml/min with the fixed fluid volume at 10 ml. RESULTS: Continuous laser activation for 10 min with the outflow rate of 10 ml/min using only 12 W resulted to continuous temperature rise to as high as 83 °C. Similar rise of temperatures were observed for 40 W and 60 W with 10 ml/min outflow rate with intermittent laser activation. With 20 and 30 ml/min outflow rates the maximum temperatures for all power settings were below the threshold (< 43 °C). However, the time to reach the same total emitted energy was 60% and 40% shorter 60 W and 40 W, respectively. CONCLUSION: Our study found that continuous laser activation with as less as 12 W using 10 ml/min outflow rate increased the irrigation fluid temperature above the threshold only after 1 min. In the current experimental setup, with the fluid outflow rate of 20 and 30 ml/min safe laser activation with 60 W and 40 W (temperature < 43 °C) can be achieved reaching the same total emitted energy as with 12 W in significantly shorter time period.

What is the impact of pulse modulation technology, laser settings and intraoperative irrigation conditions on the irrigation fluid temperature during flexible ureteroscopy? An in vivo experiment using artificial stones.

PURPOSE: To investigate the effect of different combinations of laser power settings and irrigation conditions using the pulse modulation technology of Quanta™ on irrigation fluid temperature (IFT) during FURS (flexible ureteroscopy) on an in-vivo porcine model with artificial stones. MATERIALS AND METHODS: A female pig was used. Following the insertion of artificial stones (Begostone™, BEGO USA, Lincoln, RI), a K-type thermocouple was fixed to the created percutaneous access tract. Real-time recordings of IFT during FURS were performed without UAS (ureteral access sheath), with 10/12 UAS, 12/14 UAS and 14/16 UAS. Stone fragmentation was achieved using Quanta Litho Cyber Ho 150 W™ (Samarate, Italy). The IFT was recorded for 30 s, during laser activation, with power settings of 20, 40, 60, 75 and 100 W under both manual pump and gravity irrigation. RESULTS: The IFT rise above 54 °C was recorded above a power of 40 W when gravity irrigation was used. The use of UAS prolonged the time for IFT to reach high values, although high power settings increase IFT within seconds from the laser activation. Under pump irrigation, only the 100 W power setting without the use of UAS resulted in dangerous IFT after approximately 10 s. CONCLUSION: The high-power Ho:YAG laser can cause a damaging thermal effect to the kidney exceeding the threshold of 54 °C, under gravity irrigation. Lower power settings (up to 40 W) can be used with safety. According to our experiment, when using high power settings, the use of UAS and manual pump irrigation, is the safest combination regarding renal thermal damage.

Effects of irrigation parameters and access sheath size on the intra-renal temperature during flexible ureteroscopy with a high-power laser.

OBJECTIVES: To investigate the effect of different laser power settings on intra-renal temperature (IRT) under different irrigation conditions during flexible ureteroscopy (FURS) in a live-anesthetized porcine model. METHODS: Following ethics approval, 2 female pigs weighing ~ 28 kg were used. Under general anesthesia, a percutaneous access was obtained to fix a K-type thermocouple inside the pelvi-calyceal system for real-time recording of IRT during FURS without UAS, UAS-10/12, UAS-12/14, and UAS-14/16F. A high-power holmium laser was used and the IRT was recorded during laser activation for up to 60 s at a laser power of 20 W, 40 W, and 60 W under gravity irrigation and manual pump irrigation. RESULTS: Under gravity irrigation, FURS without UAS was associated with hazardous IRT at a laser power as low as 20 W for as short as 20 s of laser activation. The IRT was rendered borderline when UAS was used. This UAS buffering effect disappeared with the use of higher laser-power settings (40 W and 60 W) with the maximal IRT exceeding 60 °C. Moreover, laser activation at 60 W was associated with very rapid increase in IRT within few seconds. Under pump irrigation, laser activation at the highest power setting (60 W) for 60 s was associated with a safe IRT, even without the use of UAS. The maximal IRT was below 45 °C. CONCLUSION: The use of high-power Ho:YAG laser carries potentially harmful thermal effect when used under gravity irrigation, even when large-diameter UAS is used. High-power settings (> 40 W) require high irrigation flow. The use of UAS is advisable to reduce the IRT and balance any intra-renal pressure increase.