Re: The Effect of Laser Fiber Cleave Technique and Lithotripsy Time on Power Output

Dear Editor:

We have read with interest the article recently published in the Journal of Endourology by Peplinski and colleagues. “The Effect of Laser Fiber Cleave Technique and Lithotripsy Time on Power Output.” The authors evaluated five different laser fiber cleaving techniques, in a randomized single-blinded study, on two holmium laser fiber diameters (200 and 365 μm), over 15 minutes of laser lithotripsy on calcium oxalate monohydrate stones. They performed the experiments 10 times for each cleaving technique, on each fiber diameter. The authors found no benefit on routinely cleaving the fibers because of the rapid fiber degradation in a laser lithotripsy. In this way, they found no benefit of using any specific cleaving technique, as the power output will be equivalent within the first few minutes.

Some considerations may be made to this study.

First, we agree with the conclusion of finding no benefit of using any specific cleaving technique. This result is consistent with the study by Kronenberg and Traxer ¹ in which no differences were found between ceramic and metal scissors when cleaving the fiber tip.

In addition, the authors stripped the fibers for each experiment, although Kronenberg and Traxer also demonstrated that coated fibers achieved higher (30%) ablation rates than stripped fibers. Metal scissors were found to be less effective than ceramic scissors in stripped fibers but equal in coated fibers.

Thus, we recommend using common surgical scissors to cut the fiber tip at the beginning of each procedure and thereafter, as they are always available and cost-effective.

Second, the pulse length has been proven to be an important element in lithotripsy and burn-back effect, as short pulse is significantly more ablative than long pulse. ^2,3 The authors did not include this parameter in their evaluations; this parameter is a key element in the experiments as the results might vary. Experiments must include both dusting and fragmentation parameters to precise their results, as they might not be the same.

Third, the most widely used cleaving tools are surgical metallic scissors, ceramic scissors, and a blade scalpel. Th diamond wheel and the cleaving pen are useful tools for basic research, although these tools are not available sterile in the market. Also the manufacturers recommend using these tools in “controlled laboratory environments”. ⁴ For these reasons, clinical applications may be limited.

Fourth, based on our clinical experience and laboratory experiments, we have data (yet unpublished) that have suggested that cutting the fiber tip every 10,000 J may be beneficial. Finally cleaving the laser fibers may bring other benefits: the fiber tip damage and cracking may allow back burns and retrograde laser emissions becoming a potential risk to damage the ureteroscope. For this reason we continuously cut the fiber tip each 10,000 J (achieved every 15 minutes of laser lithotripsy approximately).

We acknowledge the increasing interest to perform basic research in endourology to improve our working materials. We congratulate the authors for this well-designed study and we encourage them to continue.