WCE 2019: Temperature Rise During Laser Lithotripsy: Comparison of Super Pulse Thulium Fiber Laser (SPTF) vs High Power 120W Holmium-YAG Laser (Ho:YAG)

Abu Dhabi, United Arab Emirates (UroToday.com) Dr. Wilson Molina, Professor at the University of Kansas Medical Center, presented data the temperature rise differences during laser lithotripsy when using either the Super Pulse Thulium Laser Fiber (SPTF) or the High Power 120W Holmium-YAG laser (Ho:YAG). The SPTF is a new laser platform that has potentially emerged as an alternative to Ho:YAG, which is the current standard of care. This trio has had six total presentations on various aspects of the SPTF at the World Congress of Endourology 2019 and are quickly becoming the worldwide experts on this laser platform.

In this study, the group utilized ex-vivo fresh porcine kidneys and ureters headed to 37C. Their experimental setup consisted of 15 trials and a 3mm Begostone was placed in the ureter (Figure 1). Antegrade semi-rigid ureteroscopy was performed and the laser was fired in contact with the stone for 5 seconds. Continuous flow from a hand pump irrigation was used throughout the experiment. Temperature rise was measured in the ureter utilizing a thermocouple integrated to a hybrid guidewire that was placed 2mm off the stone and the other at the surface of the stone.

WCE 2019 Experimental Set Up

Lithotripsy was performed using a 200 µm core fiber at dusting (SPTF– 0.1J, 200hz, SP; Ho:YAG- 0.3J, 80hz, LP) and fragmenting (0.8J, 8Hz, SP for both) settings for 5 secs. Fifteen repetitions were recorded for each laser at each setting. Tissue samples of the ureter for each setting and system at each site of lasering were collected for histological analysis.

Dr. Molina presented data that showed despite both laser platforms inducing a temperature it remained below the threshold for cellular injury, which was confirmed on histology. The temperatures were greater for the Ho:YAG on the dusting setting (41.13C vs 40.46C, p=0.011 while the fragmenting setting, the temperature was greater for the SPTF (31.87C vs 29.3C, p=0.001).

During the discussion, Dr. William Roberts from the University of Michigan brought up concerns that clinical use of these laser fibers may, in fact, be dangerous to a patient given lasers are fired for an extended time when performing lithotripsy. Dr. Manoj Monga from the Cleveland Clinic countered by stating that the irrigation fluid they use at room temperature may negate these concerns.

Overall, the study was well received and endourologists as a whole are excited by the clinical use of the SPTF.

Presented by: Wilson Molina, MD, Professor at the University of Kansas Medical Center, Kansas City, Kansas

Written by: Roshan M. Patel, MD, Department of Urology, University of California, Irvine, California, @rpatel26, at the 37th World Congress of Endourology (WCE) – October 29th-November 2nd, Abu Dhabi, United Arab Emirates

Figure 1: Experimental Set-Up

Presented by Wilson Molina, MD

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