Abstract
Purpose
To evaluate the thermal effect of high-power holmium:yttrium–aluminum–garnet (Ho:YAG) laser lithotripsy in flexible/semirigid ureteroscopy (fURS/sURS) and percutaneous nephrolithotomy (PNL) in a standardized ex vivo porcine kidney model with real-time temperature assessment.
Methods
The experimental setup consisted of three models designed to evaluate the thermal effects of Ho:YAG laser lithotripsy in fURS, sURS and PNL, respectively. In all setups, a postmortem porcine kidney was placed in a 37 °C water bath. Three thermocouples were inserted into the renal parenchyma while a flexible thermocouple was placed 3–4 mm proximal to the laser fiber to measure temperature variations in the collecting system. The thermal impact was evaluated in relation to laser power between 5 and 100 W and various irrigation rates (37 °C, 0–100 ml/min).
Results
In all three experimental setups, sufficient irrigation was required to prevent potentially damaging temperatures into the renal pelvis and parenchyma. Even 5 W in fURS can lead to a potentially harming temperature rise if insufficient irrigation is applied. Particularly, high-power settings ≥ 30 W carry an elevated risk for critical temperature rises. The results allow the definition of a specific irrigation threshold for any power setting to prevent critical temperatures in the present study design.
Conclusions
Ho:YAG laser lithotripsy bears the risk of thermal damages to the urinary tract even at low-power settings if inadequate irrigation is applied. Sufficient irrigation is mandatory to perform safe Ho:YAG laser lithotripsy. Based on the results, we developed a formula calculating the approximate ΔT for irrigation rates ≥ 30 ml/min: ΔT = 15 K × (power [W]/irrigation [ml/min]).
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Abbreviations
- fURS:
-
Flexible ureteroscopy
- sURS:
-
Semirigid ureteroscopy
- PNL:
-
Percutaneous nephrolithotomy
- K:
-
Kelvin
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Acknowledgements
We would like to thank Michaela von Aichberger for the illustrations in this publication and the institutional funding, Faculty of Medicine, University of Freiburg, Germany.
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SH: protocol/project development, data collection and management, data analysis, manuscript writing/editing, and illustrations; RP: data collection and management, data analysis, manuscript and figure writing/editing, and performed experiments; RS: manuscript editing; PFM: illustrations editing; MS: manuscript writing/editing and supervision; AM: protocol/project development, manuscript writing/editing, and supervision.
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This work was supported by material support of LISA Laser products (Katlenburg-Lindau, Germany). Simon Hein: German Federal Ministry of Education and Research, Berlin, GER—research funding Germany (unrelated to the present work). Rodrigo Suarez-Ibarrola: German Federal Ministry of Education and Research, Berlin, GER—research funding Germany (unrelated to the present work). Philippe-Fabian Müller: German Federal Ministry of Education and Research, Berlin, GER—research funding Germany (unrelated to the present work). Martin Schoenthaler: consultant contracts with NeoTract Inc., Pleasanton, USA and Trokamed GmbH, Geisingen, Germany (unrelated to the present work). Arkadiusz Miernik: German Federal Ministry of Education and Research, Berlin, GER—research funding, German Association of Urology, Düsseldorf, GER—travel sponsoring, European Association of Urology, Arnhem, NL—travel sponsoring, Walter de Gruyter, Berlin, GER—royalties, RichardWolf GmbH, Knittlingen, GER—speaker’s fee, KLS Martin, Tuttlingen, GER—advisor, Avatera medical, Jena, GER—advisor, Lisa laser OHG, GER—proctor, Schoelly fiber optics GmbH, GER—advisor, Optimed GmbH, Ettlingen, GER—advisor (unrelated to the present work).
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There are no human participants or animals involved in the study. Human stone probes were analyzed after ethical approval (IRB approved protocol number: 79/16 leading ethics committee: Ethik-Kommission der Albert-Ludwigs-Universität Freiburg, Germany) and written informed consent.
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Hein, S., Petzold, R., Suarez-Ibarrola, R. et al. Thermal effects of Ho:YAG laser lithotripsy during retrograde intrarenal surgery and percutaneous nephrolithotomy in an ex vivo porcine kidney model. World J Urol 38, 753–760 (2020). https://doi.org/10.1007/s00345-019-02808-5
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DOI: https://doi.org/10.1007/s00345-019-02808-5