Automated irrigation systems in mitigating laser-induced temperature during simulated ureteroscopy

To compare the temperature changes with laser activation when providing irrigation with a pressure bag vs a fluid management system (FMS).

Benchtop experiments were performed with a LithoVue™ Elite (Boston Scientific Corp., Marlborough, MA, USA) flexible ureteroscope placed through an 11/13-F ureteric access sheath into a benchtop pelvicalyceal kidney model. Room temperature saline irrigation, via the scope, was provided either with a pressure bag or FMS. Both systems were pressurised to 200 mmHg and left for 10 min. After 10 min, a holmium:yttrium-aluminium-garnet laser was activated at 20, 40, or 60 W for 90 s. Flow rate, irrigation pressure, intrarenal pressure and calyceal temperature were recorded continuously. Experiments were repeated five times. Benchtop empirical temperature data were compared to mathematical model predictions. The mathematical model was then used to predict calyx temperature as a function of flow rate in in vivo conditions.

Pressure-bag irrigation flow rate declined from ~38 to ~25 mL/min (36%) over 10 min, whereas the FMS maintained stable flow of ~45 mL/min. Intrarenal pressure remained ≤30 mmHg in all experiments. Consequently, the benchtop calyx mean (standard deviation) temperature rise with pressure bag vs FMS irrigation was: at 20 W 7.9 (1.0)°C vs 6.4 (0.6)°C (P = 0.02); at 40 W 12.8 (3.2)°C vs 10.3 (1.7)°C (P = 0.15); at 60 W 17 (3.4)°C vs 12.4 (1.2)°C (P = 0.02).

Irrigation flow rate is a key determinant of thermal risk during laser lithotripsy. An automated FMS can maintain consistent flow; mitigating temperature rise and thermal dose in a benchtop model.