Presentation Authors: Paul Chiron*, Saint Mandé, France, Steeve Doizi, Vincent De Coninck, Etienne Xavier Keller, Laurent Berthe, Olivier Traxer, Paris, France
Introduction: Thulium Fiber Laser (TFL) is being explored as an alternative to Holmium:YAG Laser, as its wavelength of 1940 nm more closely matches the water absorption peak, providing an absorption coefficient about five times higher. The aim of this study was to investigate "caliceal" fluid temperature changes during TFL lithotripsy, using settings from 6 to 50W power output, with different irrigation flow rates.
Methods: The experimental system consisted of a silicone kidney model (NeodermaÂ®) filled with physiological serum and immerged into a saline bath maintained at 37.5Â°C temperature. Real-time temperature was recorded using a thermocouple (PC Sensor) positioned at a distance of 5 mm from the fiber tip. A 200, 272 and 365 Âµm laser fiber (Rocamed) was introduced through the working channel of a disposable ureteroscope (LithoVue; Boston Scientific). Saline irrigation at room temperature was delivered through the working channel of the ureteroscope, at flow rates of 0, 19, and 38 mL/minute. A 50W TFL (IPG Photonics) was used. Several settings were explored, for three power outputs (6, 25 and 50W). During each experiment, the laser was activated continuously for 5 minutes.
Results: Temperature increased with increasing laser power output and decreasing irrigation flow rate. The highest increase, 79.0Â°C (standard deviation 3.2), occurred with an average power output of 50W and no irrigation after 5 minutes of continuous laser firing. None of the tested laser settings and irrigation parameters produced temperature exceeding 50Â°C when activated for only 1 minute of continuous laser firing. High irrigation flow permitted in every cases to limit heat generation at less than 7Â°C.
Conclusions: With most of laser settings, adequate irrigation can maintain stable temperatures in an in vitro kidney model. As irrigation rates decrease, even lower power settings produce a significant increase in maximum temperature, potentially leading to urothelial tissues injuries.Awareness of this risk allows urologist to implement a variety of techniques (higher irrigation flow rates, intermittent laser activation, cooled irrigation fluid, avoidance of highest power settings) to limit thermal lesions during TFL lithotripsy.