Evaluation of a new 240-μm single-use holmium:YAG optical fiber for flexible ureteroscopy

Laser accessories: surgical fibers, strippers, cleavers, and protective glasses

PURPOSE OF REVIEW

This review provides most recent findings and developments relating to surgical laser fibers, strippers, cleavers, and protective glasses.

RECENT FINDINGS

The smallest core diameter that can be used with Holmium:YAG lasers is 200 μm. Smaller core diameter fibers can be used with the Thulium fiber laser and offer better flexibility and lower risk of fracture, at the risk of greater burnback effect. Misleading discrepancies between the true diameter of laser fibers and their packaging labels must be considered. Fiber tip degradation from the burnback occurs within few minutes, thus questioning the need for time-consuming fiber tip reprocessing with fiber strippers and special cleaving tools. This shortcoming also applies to instrument-protecting ball-tip fibers. Cleavage of fiber tips through their protective jackets ('coated tips') is a cheaper alternative for instrument protection, additionally offering better visual control of the fiber tip. Third-generation side-firing greenlight laser fibers are still prone to rapid deterioration. Laser eyewear does not seem necessary for Holmium:YAG applications, whereas laser-specific protective glasses should be worn for greenlight laser applications.

SUMMARY

With better understanding of laser accessories, practicing urologists may tailor their practice to reach optimal efficacy and safety for Holmium:YAG, Thulium fiber laser and Greenlight laser applications.

Superpulse thulium fiber laser lithotripsy: an in vitro comparison of 200 μm and 150 μm laser fibers

PURPOSE

To investigate the thermal effects, stone retropulsion and ablation rate of SuperPulse Thulium-fiber laser (SP TFL) with two different surgical fibers of 200 and 150 μm in diameter.

METHODS

SP TFL (NTO IRE-Polus, Fryazino, Russia) performance with 200 and 150 μm fibers (NTO IRE-Polus, Fryazino, Russia) was evaluated. Before each test, the laser fiber was cleaved, and the power measurement was taken to verify the actual laser output power. To compare the laser fibers in well-controlled environments, a number of setups were used to assess retropulsion, ablation efficacy, fiber burnback, energy transmission, and safety.

RESULTS

Power measurements performed before each test revealed a 4.7% power drop for a 200 μm fiber SP TFL (14.3 ± 0.5 W) and 7.3% power drop for a 150 μm fiber SP TFL (13.9 ± 0.5 W) versus the nominally indicated power (15.0 W). Retropulsion with the TFL was minimal and comparable between fibers. We found no clinically relevant temperature differences between SP TFL with either 200 or 150 μm fibers. The ablation efficacy tended to be comparable under most parameters. Yet, we did observe a decreased diameter of residual fragments after the ablation with a 150 μm fiber.

CONCLUSION

The smaller fiber (150 μm) is not inferior to 200 μm fiber in terms of fiber burnback, retropulsion, safety, and ablation rate. Moreover, it has the potential to decrease the diameter of fragments during lithotripsy, which may facilitate dusting during RIRS.

Comparison of Holmium:YAG and Thulium Fiber Lasers on the Risk of Laser Fiber Fracture

Objectives: To compare the risk of laser fiber fracture between Ho:YAG laser and Thulium Fiber Laser (TFL) with different laser fiber diameters, laser settings, and fiber bending radii. METHODS: Lengths of 200, 272, and 365 μm single use fibers were used with a 30 W Ho:YAG laser and a 50 W Super Pulsed TFL. Laser fibers of 150 µm length were also tested with the TFL only. Five different increasingly smaller bend radii were tested: 1, 0.9, 0.75, 0.6, and 0.45 cm. A total of 13 different laser settings were tested for the Ho:YAG laser: six fragmentation settings with a short pulse duration, and seven dusting settings with a long pulse duration. A total of 33 different laser settings were tested for the TFL. Three laser settings were common two both lasers: 0.5 J × 12 Hz, 0.8 J × 8 Hz, 2 J × 3 Hz. The laser was activated for 5 min or until fiber fracture. Each measurement was performed ten times. Results: While fiber failures occurred with all fiber diameters with Ho:YAG laser, none were reported with TFL. Identified risk factors of fiber fracture with the Ho:YAG laser were short pulse and high energy for the 365 µm fibers (p = 0.041), but not for the 200 and 272 µm fibers (p = 1 and p = 0.43, respectively). High frequency was not a risk factor of fiber fracture. Fiber diameter also seemed to be a risk factor of fracture. The 200 µm fibers broke more frequently than the 272 and 365 µm ones (p = 0.039). There was a trend for a higher number of fractures with the 365 µm fibers compared to the 272 µm ones, these occurring at a larger bend radius, but this difference was not significant. Conclusion: TFL appears to be a safer laser regarding the risk of fiber fracture than Ho:YAG when used with fibers in a deflected position.

The Effect of Holmium Laser Fiber Bending Radius on Power Delivery During Flexible Ureteroscopy

Introduction: Flexible ureteroscopy is a mainstay of upper urinary tract stone treatment. Holmium laser lithotripsy is a particularly common and notable technique for the dusting and fragmenting of renal stones. During ureteroscopy, optical fibers are subject to sharp bends in pursuit of stones, particularly those at the lower pole. Following from principles of fiber optics, subjecting these fibers to sharp bending angle has the potential to reduce the efficiency of power transmission at the fiber tip. Due to the potential implications this hypothesis could have on endourological practice and research, we aimed to explore the potential impact of fiber bending on end-fiber power output. Materials and Methods: Using a highly sensitive oscilloscope and a urological holmium laser, we assessed the end-fiber power output under a variety of bending conditions. To ensure maximal confidence in our results, the maximal bending conditions explored substantially exceeded any condition, which could occur during ureteroscopic surgery. Results: We found evidence that bending radius alone has a clinically insignificant impact on the light power transmission in the fiber. At certain bending conditions, we observed a clinically unimportant but statistically significant reduction in power transmission. This was verified using two commonly used delivery fiber types exposed to 8-second bursts for each bending condition.

Clinical efficacy and safety of flexible ureteroscopic lithotripsy using 365 μm holmium laser for nephrolithiasis: a prospective, randomized, controlled trial

PURPOSE

To compare the clinical efficacy and safety between the FURL with 365 μm and 200 μm holmium laser for treating nephrolithiasis.

MATERIALS AND METHODS

A prospective randomized controlled trial was performed including analysis of data from 200 patients with nephrolithiasis. A total of 180 patients were randomized into two groups according to 1:1 ratio. In the 365 μm holmium laser group, kidney stones were disintegrated into less than 2 mm fragments with a 365 µm holmium laser fiber with the settings of 30-45 W under direct visualization; in the control group, the conventional 200 μm holmium laser was used. Descriptive statistics and logistic regression analyses tested the association among operation time, stone-free rate (SFR) and incidence of complications.

RESULTS

Operation time in the FURL with 365 μm laser was significantly shortened and no significance was observed in the complication rate. Stone size and location were identified as two major confounding factors for the operation time and SFR. Moreover, the FURL using 365 μm laser showed less operation time for renal stones with the diameter between 1 and 2 cm, stones located in lower calyx and multiple calculi; stones larger than 2 cm and/or located in lower pole inclined to present better SFR using the FURL with 365 μm laser.

CONCLUSIONS

The FURL combined with 365 μm holmium laser is safer and highly efficacious for the management of nephrolithiasis when compared to conventional FURL procedures, especially for those located in lower pole and larger than 2 cm.

Laser Fibers for Holmium:YAG Lithotripsy: What Is Important and What Is New

Holmium:YAG laser is currently the dominant lithotripter used during retrograde intrarenal surgery. The laser energy is delivered to the target via flexible optical laser fibers. The performance characteristics of laser fibers vary. The diameter, flexibility, resistance to fracture with bending, and tip configuration are all important factors that contribute to a fiber's overall performance. Understanding these characteristics assists the end user with proper fiber selection for procedures.

Comparison of flexible ureteroscopy damage rates for lower pole renal stones by laser fiber type

OBJECTIVES

Laser lithotripsy, often used during ureteronephroscopy (URNS), requires the Ho:YAG optical fiber transmit energy via total internal reflection (TIR). In critical lower pole deflections, energy may refract into the cladding causing fiber failure and scope damage. New optical fiber technology aims to have increased tolerance for high degrees of flexion. We compared two brands of laser fibers with sub-300 micron cores (Sureflex, Boston Flexiva) to determine failure rates and scope repair costs.

METHODS

A retrospective cohort study comparing these two fibers for patients at a single academic institution who underwent flexible URNS with laser lithotripsy was performed from September 2013 to October 2015. Preoperative imaging was evaluated for stone burden and location. Intraoperative variables were collected, including energy use, lower pole lasering, laser fiber malfunction, and scope damage. The primary outcome was scope damage caused by laser fiber malfunction. Secondary outcome was scope repair costs. Fisher's exact test and two tailed t-tests were used.

RESULTS

Of 223 subjects, 143 met inclusion criteria, and 8 had laser fiber failure. All failures occurred with the Sureflex fiber (8 of 63, 13%) vs the Boston Flexiva fiber (0 of 80, 0%) (P < 0.01). Malfunctions occurred in 8 of 79 lower pole stone applications versus 0 of 64 non-lower pole stone laser applications (P < 0.01). No other risk factor was different between fiber cohorts, except energy setting. Scope repair cost averaged $9155 CDN, yielding an average repair cost per case of $1144 CDN for the Sureflex versus $0 for the Boston fiber (P < 0.01).

CONCLUSIONS

Both optical fibers perform well in non-lower pole locations. However, the challenge for laser fibers in lower pole URNS is to maintain TIR. Fiber failure reflects an inability to maintain reflection and is not based on energy used or stone burden. The Boston Flexiva laser fiber has fewer failures, resulting in $0 repair cost per case, compared to the Sureflex fiber in URNS with an average repair cost of $1144 CDN per case. Lasers Surg. Med. 50:798-801, 2018. © 2018 Wiley Periodicals, Inc.

Intracorporeal lithotripsy

Since the introduction of ESWL, PNL and URS during the early 1980s the application rate of ESWL has declined while those of PNL and URS have increased. This is mainly due to the facts that instruments and techniques for Intracorporeal Lithotripsy (IL) have made a continuous progress. This review shows that today an array of options for IL within the entire urinary tract is available to treat stones in a perfect minimal invasive way. At the same time further improvements of IL are already visible.

A Comparative in Vitro Study of Power Output Deterioration over Time Between Ho:YAG Laser Fibers from Different Manufacturers as a Function of Deflection and Power Input

OBJECTIVES

To investigate the performance of laser fibers from 6 major manufacturers in vitro and to identify the effect of time and angulations (180° and 0°) on fiber power output.

MATERIALS AND METHODS

Overall, 36 single-use fibers were used. Each was tested with an energy input of 0.8, 1.4 and 2.0 Joules. A power detector measured power output after 1, 5, 10 and 15 minutes for three 15-minute cycles of continuous use. For the first 2 cycles, the fiber was bent to 180° with the use of a pre fabricated mould. Analysis of the data was performed by ANOVA and Tukey's test when the results were significant amongst groups. Statistical significance was deemed p < 0.05.

RESULTS

No fiber fracture occurred. There was no significant difference in output at 15 minutes of continuous use at 0° and 180°. The reduction in energy output at the 15th minute of continuous use at 180° was not significant for any fiber type or initial input. Only output differences between the fibers proved to be significant (p = 0.001).

CONCLUSION

Fiber fracture and decline in performance is not due to deflection and continuous use. Frictional forces that occur between the fiber tip and the stone fragments may be responsible.

The truth about laser fiber diameters

OBJECTIVE

To measure the various diameters of laser fibers from various manufacturers and compare them with the advertised diameter.

METHODS

Fourteen different unused laser fibers from 6 leading manufacturers with advertised diameters of 200, 270, 272, 273, 365, and 400 μm were measured by light microscopy. The outer diameter (including the fiber coating, cladding, and core), cladding diameter (including the cladding and the fiber core), and core diameter were measured. Industry representatives of the manufacturers were interviewed about the diameter of their fibers.

RESULTS

For all fibers, the outer and cladding diameters differed significantly from the advertised diameter (P <.00001). The outer diameter, which is of most practical relevance for urologists, exhibited a median increase of 87.3% (range, 50.7%-116.7%). The outer, cladding, and core diameters of fibers with equivalent advertised diameters differed by up to 180, 100, and 78 μm, respectively. Some 200-μm fibers had larger outer diameters than the 270- to 273-μm fibers. All packaging material and all laser fibers lacked clear and precise fiber diameter information labels. Of 12 representatives interviewed, 8, 3, and 1 considered the advertised diameter to be the outer, the cladding, and the core diameter, respectively. Representatives within the same company frequently gave different answers.

CONCLUSION

This study suggests that, at present, there is a lack of uniformity between laser fiber manufacturers, and most of the information conveyed to urologists regarding laser fiber diameter may be incorrect. Because fibers larger than the advertised laser fibers are known to influence key interventional parameters, this misinformation can have surgical repercussions.

Optimizing use of the holmium:YAG laser for surgical management of urinary lithiasis

The holmium:yttrium aluminum garnet (Ho:YAG, holmium) laser is an intracorporeal lithotrite that is widely used in the surgical management of urinary lithiasis. The Ho:YAG laser is capable of fragmenting urinary stones of all compositions while maintaining a wide margin of safety. The 2140-nm wavelength of energy is transmitted from the generator to the stone using specialized silica optical fibers. The effectiveness of the laser can be impacted by the type of laser fiber used, the pulse energy and frequency settings, and the composition of the stone. This paper provides an overview of Ho:YAG laser fibers utilized for lithotripsy during ureteroscopy. We will also review current data regarding optimal energy settings and discuss our experience with different fragmentation techniques.

Update on lasers in urology 2014: current assessment on holmium:yttrium-aluminum-garnet (Ho:YAG) laser lithotripter settings and laser fibers

PURPOSE

The purpose of the study was to review the existing literature on holmium:yttrium-aluminum-garnet laser lithotripsy regarding lithotripter settings and laser fibers.

METHODS

An online search of current and past peer-reviewed literature on holmium laser lithotripsy was performed on several databases, including PubMed, SciElo, and Google Scholar. Relevant studies and original articles about lithotripter settings and laser fibers were examined, and the most important information is summarized and presented here.

RESULTS

We examine how the choice of lithotripter settings and laser fibers influences the performance of holmium laser lithotripsy. Traditional laser lithotripter settings are analyzed, including pulse energy, pulse frequency, and power levels, as well as newly developed long-pulse modes. The impact of these settings on ablation volume, fragment size, and retropulsion is also examined. Advantages of small- and large-diameter laser fibers are discussed, and controversies are highlighted. Additionally, the influence of the laser fiber is examined, specifically the fiber tip preparation and the lithotripter settings' influence on tip degradation.

CONCLUSIONS

Many technical factors influence the performance of holmium laser lithotripsy. Knowing and understanding these controllable parameters allows the urologist to perform a laser lithotripsy procedure safely, efficiently, and with few complications.

Disposable devices for RIRS: where do we stand in 2013? What do we need in the future?

PURPOSE

Disposable devices for retrograde intrarenal surgery (RIRS) form a significant part of the urologist's armamentarium for the endoscopic management of urologic diseases. Herein, we provide an overview of the literature regarding the advances and controversies of these devices.

METHODS

A PubMed search was used to identify the literature discussing the subject of disposable devices for RIRS. Articles published between 2012 and 2013 were considered.

RESULTS

Ureteral access implements including access sheaths, wires, and dilators are an area of both improvement and controversy regarding their proper use. The safety, effectiveness, and limitations of lithotrites continue to be refined. Stone retrieval devices are undergoing persistent miniaturization, and their use may prove to be cost effective. The debate over perioperative stenting remains, while symptom management is explored. A cost-effective option for disposable flexible ureteroscopy shows promise.

CONCLUSIONS

While rapid advances in technology and knowledge continue, continual improvements are necessary. Disposable equipment needs persistent refinement and possible miniaturization. More efficient fragment retrieval devices are needed. Durability of laser fibers and safety within ureteroscopes needs to be improved. Reducing stent morbidity remains an ongoing challenge. Lastly, costs need to be reduced by the further development of disposable flexible ureteroscopes and in the recyclability of disposable devices to improve availability worldwide.