Factors affecting the thermal effects of lasers in lithotripsy—a literature review

Abstract

ObjectiveThe use of lasers has been an important part of urology in the treatment of stone and prostate disease. The thermal effects of lasers in lithotripsy have been a subject of debate over the years. The objective of this review was to have an understanding about the current state of knowledge available on thermal effects of lasers in lithotripsy, as well as explore any new areas where studies are needed. MethodsIn August 2022, a keyword search on Google Scholar, PubMed and Scopus for all papers containing the phrases “thermal effects” AND “laser” AND “lithotripsy” AND “urology” was done followed by citation jumping to other studies pertaining to the topic. Those pertaining to lasers in other aspects of urology besides lithotripsy were excluded and 35 relevant papers were included in our study. The data from relevant papers were segregated into six groups according to the factor studied/type of study, and tables were created for a comparison of data. ResultsTemperature above the threshold of 43 °C was reached only when the power was >40 W and when there was adequate irrigation (at least 15–30 mL/min). Shorter lasing time divided by lithotripsy time or operator duty cycle less than 60%–70% also resulted in a smaller temperature rise. ConclusionAt least eight factors modify the thermal effects of lasers, most importantly the use of chilled irrigation at higher perfusion rates, lower power settings <40 W, and with shorter operator duty cycle will help to prevent thermal injuries from occurring. Stones impacted in the ureter or pelvi-ureteric junction further increase the probability of thermal injuries during laser firing.