Abstract
The authors describe an in vitro simulation of ureteroscopic holmium:YAG (Ho:YAG) laser lithotripsy. They measured the temperature in a ureteral model. Temperatures rose from baseline 37°C to >43°C within 2 seconds of free running laser emission at 1 J at 20 Hz and 0.2 J at 80 Hz. Even 1 J at 10 Hz reached a temperature >43°C after 15 seconds continuous activation. Temperature rise was attenuated by increased irrigation pressures.
Ho:YAG laser energy is well absorbed by water. 1 Not surprisingly, the authors demonstrate that increased power settings produce temperature elevations that could potentially cause adverse effects to the ureter (and to a lesser extent, the kidney). These temperature increases were attenuated by using high-pressure irrigation or by taking laser “rests” so that the energy was not constantly being dumped into the aqueous environment. Although there have not been clinical reports of laser-induced heat injuries to the ureter, admittedly it has only been the past few years that dusting and high-power Ho:YAG laser lithotripsy practice has become commonplace. 2,3
I infer if high-power laser settings are to be used (>3.6 W in this study), the safest clinical practice would be to employ frequent rests, or deliver high-pressure irrigation with a hand pump.