Chilled Irrigation for Control of Temperature Elevation During Ureteroscopic Laser Lithotripsy: In Vivo Porcine Model

Introduction: Multiple studies have shown significant heating of fluid within the urinary collecting system with high-power laser settings. Elevated fluid temperatures may cause thermal injury and tissue damage unless appropriately mitigated. A previous in vitro study demonstrated that chilled (CH) (4 degrees C) irrigation slowed temperature rise, decreased plateau temperature, and lowered thermal dose during laser activation with high-power settings. We sought to evaluate the thermal effects of CH, room temperature (RT), and warmed (WM) irrigation during ureteroscopy with laser activation in an in vivo porcine model.Materials and Methods: Seven female Yorkshire cross pigs (45-55 kg) were anesthetized and positioned supine. Retrograde ureteroscopy was performed with a thermocouple affixed 5 mm from the distal end of the ureteroscope. In two pigs, a holmium:YAG laser was activated for 60 seconds at irrigation rates of 8, 12, and 15 mL/min with CH, RT, or WM irrigation. In five pigs, core body temperature was recorded for 1 hour with or without continuous CH irrigation at 15 mL/min.Results: At irrigation rates >= 12 mL/min, temperature curves appeared uniformly offset, WM > RT > CH irrigation. The threshold of thermal tissue injury was reached during laser activation for all irrigation temperatures at 8 mL/min. The threshold was not reached with CH irrigation at 12 or 15 mL/min, or with RT irrigation at 15 mL/min. The threshold was exceeded at all irrigation rates with WM irrigation. There was no significant change in core body temperature after delivering CH irrigation at 15 mL/min compared with no irrigation for 60 minutes.Conclusion: Irrigation with CH saline solution during ureteroscopic laser lithotripsy slows temperature rise, lowers peak temperature, and lengthens the time to thermal injury compared with irrigation with RT or WM saline solutions. Core body temperature was not significantly impacted by CH irrigation.