Laser, irrigation, and suction settings to optimize intra-renal temperature and pressure during automated laser lithotripsy in an ex vivo study part I

This study evaluated the effects of various laser, irrigation, and suction parameters on intra-renal temperature (IRT) and pressure (IRP) using an ex vivo porcine kidney. We introduced a novel Laser: Stop ratio (LS ratio), which automatically balances activation and resting periods. Only kidneys with a 10 mL pelvo-calyceal volume were used to assess the parameters [Thulium fiber laser (TFL) and Holmium: Yttrium-Aluminum-Garnet (Ho: YAG): 1.0 J/20Hz, 0.5 J/40Hz], pump-based irrigation of 30 mmHg (P30) and 50 mmHg (P50), LS ratios from 2:4 to 12:4, and continuous laser activation, with or without the flexible and navigable suction ureteral access sheath (FANS-UAS). With FANS-UAS, a Laser: Active suction: Rest ratio of 4:2:4 was applied at 200 mmHg suction. IRT and IRP were recorded every 30 s for 15 min, with dangerous thresholds set at > 50 °C for over 1 min or > 56 °C at any time. Under P30 and P50, the IRP remained below safety thresholds. Regarding IRT, for P30, TFL (1.0 J/20Hz) allowed unlimited pop-dusting at lower LS ratios (2:4), while TFL (0.5 J/40Hz) supported this even at higher LS ratios (4:4). Ho: YAG enabled longer pop-dusting durations, particularly at higher LS ratios (6:4) with adequate resting time. For P50, pop-dusting was unlimited at all settings with an LS ratio of 12:4 with adequate resting time. FANS-UAS allowed continuous pop-dusting. The LS ratio may offer insights into automatic laser fragmentation by balancing safety and efficiency. These findings suggest practical strategies for automated laser activation in robot-assisted flexible ureteroscopy.