The purpose of this study was to investigate the factors influencing the thermal effects of holmium laser lithotripsy of urinary calculi and its safety.

We constructed an in vitro model of holmium laser thermal effect, then studied the affected factors about thermal effects of holmium laser lithotripsy: different power and energy patterns (1.0 J×10 hz, 0.5 J×20 hz, 1.0 J×20 hz, 2.0 J×20 hz), the perfusion fluid temperature (20 ℃ physiological saline, 37 ℃ physiological saline), the infusion speed (0 ml/min, 10 ml/min, 16 ml/min), optical fiber diameter (200, 365, 550 μm dahua holmium laser optical fiber), gravel model (gravel group and empty group). The holmium laser stimulated 120 s, during which the electronic thermometer measured and recorded temperature inside and outside the model each second. Each group experiments were repeated 3 times, and the average value of the three groups of experimental data was taken as the final experimental result. Independent sample T test or One-way ANOVA was used for comparison between groups. The optimal scale regression method was used to construct the influencing factor model of holmium laser thermal effect, and P<0.05 was considered as statistically significant difference.

As the test begins, the temperature in the test tube increased rapidly, at around the 40 s, the temperature reached the plateau stage, and then the temperature tend to be stable. The results of optimal scale regression analysis showed that power and energy mode (F=18.533, P<0.05), perfusion velocity (F=220.461, P<0.01; F=495.783, P<0.01; F=32.287, P<0.01; F=429.237, P<0.01), perfusion liquid temperature (t=-4.657, P<0.01; t=-4.91, P<0.01; t=-4.157, P<0.05; t=-2.933, P<0.05) and fiber diameter (F=15.88, P<0.01; F=137.053, P<0.01; F=413.411, P<0.01; F=106.437, P<0.01) were the influencing factors of the thermal effect of holmium laser, and the difference was statistically significant (F=228.857, P<0.01).

The power and energy of holmium laser, perfusion rate, perfusion temperature and fiber diameter were the influencing factors of the thermal effect of holmium laser. Reducing the power of holmium laser, increasing the perfusion speed, using fiber with small diameter and choosing normal temperature perfusion solution were all helpful to reduce the thermal effects of holmium laser.

Holmium laser; Thermal effect; Model in vitro