RE: Winship et al.,The Rise and Fall of High Temperatures During Ureteroscopic Holmium Laser Lithotripsy (From: Winship B,Wollin D,Carlos E,et al. J Endourol 2019;33:794–799;DOI: 10.1089/end.2019.0084)

Dear Editor:

In the past few years, publications about laser lithotripsy and temperature have increased. This resembles the concerns of the endourologic community some years ago about the intrarenal pressure. We are aware that the intrarenal environment changes during treatment and that these changes can become complications. ¹ Winship and colleagues ² recently communicate an in vitro study of how temperature changes are depending on the instrument, irrigation, and laser settings in a ureteral model. Based on their results, the authors suggest that to overcome high temperature in the ureter there are three strategies: increase irrigation, intermittent laser activation with pauses, and/or consider low power settings.

We congratulate the authors for their report and contribution to this topic. However, we would like to discuss some points that worry us.

The use of high power settings has demonstrated to increase temperature and subsequent renal damage. ³ One of the solutions that is usually discussed is to increase irrigation, but with that measure, we also increase the intrarenal pressure. The authors suggest to work with pressures of 100–200 mm Hg, which is equal to having the saline bag hanging 1.35–2.70 m above the patient. Remember that the normal intrarenal pressure is in the range of 0–15 mm Hg. ¹ If we are also concerned about intrarenal pressure, it appears as a poor alternative to overcome high temperature.

One of the pillars of using high-power lasers is to increase speed and diminish operative time, but if we use the laser for 3–4 seconds and wait for another 3–4 seconds, as the authors suggest, the time used to treat the stone should be double and one of the benefits of the high power settings is lost. So it does not appear to be a good measure.

The third suggestion is to change to low power settings, to maintain a safety temperature. We think this is the best measure to adopt, not because we do not like high power settings, but because it is safe in terms of temperature and also gives more control to the surgeon. The more control we have during lasering, the less damage we will do to the mucosa. A meta-analysis already reported that treating ureteral stones with laser increased stenosis as compared with pneumatic energy. ⁴ We think that with the increasing use of laser and subsequent lesions during treatment there is an underdiagnosis of silent stenosis, and we are concerned about the potential future complications of the promotion of high power settings.

Using low frequency but ensuring that every trigger from the laser hits the stone improves the performance and efficiency of the technique and makes it safer for our patients.

Further studies are needed, but the data appear to hint that high power settings cause changes in the intrarenal environment, which are difficult to overcome with reasonable measures.