Holmium: YAG laser damage to ureteral guidewire

Resistance of different guidewires to laser injury: an in-vitro experiment

BACKGROUND

In urology, lasers are used in a variety of endoscopic procedures such as ureteroscopy and retrograde renal surgery for stone fragmentation of urinary calculi and ablation of urothelial tumors. To perform these procedures, guidewires are used as a preliminary safe-mainstay for referencing the urinary tract. This study aims to determine the effect of two different lasers: holmium:YAG (Ho:YAG) and thulium:YAG (Tm:YAG) lasers on metal guidewires with PTFE coating (PTFE), nitinol guidewires with hydrophilic coating (Hydrophilic) and nitinol guidewires with hydrophilic listed coating (Zebra).

METHODS

Different combinations of frequency (5, 10 and 12 Hz) and energy per pulse (0.5, 1.5, and 2.6 J) of Ho:YAG laser were applied on the three kinds of guidewires in two experiments (50 J vs. 100 J of total energy). For the Tm:YAG laser three power levels (5, 35, and 70 W) with a total energy of 100 J were applied to the guidewires. The degree of damage (0 to 5) of the guidewire was assessed after each laser application.

RESULTS

A higher degree of injury of guidewires was related to higher values of total energy used for the Ho:YAG laser (P=0.036), and to higher values of power applied with the Tm:YAG (P=0.051). The most resistant guidewire to Ho:YAG laser energy was Zebra, followed by PTFE and Hydrophilic (P<0.001). With the Tm:YAG laser, PTFE guidewire appears to be the most resistant and the Hydrophilic the most fragile, although without reaching the statistical significance (P=0.223).

CONCLUSIONS

Both lasers revealed a harmful effect on the three tested guidewires. There was an association between the degree of injury and the amount of Ho:YAG laser energy and Tm:YAG laser power. The guidewire Zebra proved to be the safest when using Ho:YAG laser and the PTFE guidewire the most resistant to laser Tm:YAG. Further studies are necessary to confirm these results.

Successful treatment of stent knot in the proximal ureter using ureteroscopy and holmium laser

Knotted ureteral stent is rare yet tedious complication that might represent a treatment challenge to the endourologist. Only twelve cases of knotted stent have been reported. Different management options have been reported, including simple traction, ureteroscopy, percutaneous removal, and open surgery. In this paper, we present the successful untying of the knot using ureteroscopy with holmium laser.

Impact of collateral damage to endourologic tools during laser lithotripsy--in vitro comparison of three different clinical laser systems

BACKGROUND AND PURPOSE

During laser lithotripsy, working instruments are often in close proximity to the distal fiber tip and may be damaged accidentally or even intentionally. The aim of this study was to compare the amount of damage to a standard guidewire and the nitinol wires of endourologic retrieval baskets that were affected by three different clinically available laser systems.

MATERIALS AND METHODS

The impact of pulsed laser irradiation on a standard hydrophilic guidewire and a retrieval basket were investigated. One infrared (IR) laser system (holmium:yttrium-aluminum-garnet [Ho:YAG]: λ = 2100 nm) and two laser systems emitting light in the visible (VIS) spectral range (frequency-doubled double-pulse neodymium:YAG [FREDDY]: λ = 532 nm/1064 nm and flashlamp pulsed dye [FLPD]: λ = 598 nm) were used. Experimental parameters were fiber core diameter, laser pulse energy, and distance between the fiber tip and the investigated tool. Damage was evaluated by microscopic investigation and by quantifying the damage size and magnitude by creating laser impact related damage factors.

RESULTS

After application of one single laser pulse, IR-laser related maximum damage to guidewires occurred, depending on the pulse energy and the fiber core diameter, either in contact mode or in a distance of maximum 2 mm. Maximum VIS-laser related damage occurred in a distance range of 2 to 3 mm. The nitinol wires of the extraction tools could be destroyed completely by IR laser irradiation at pulse energies E(P) > 1200 mJ, depending on the fiber core diameter used. VIS lasers were solely able to set visible damage to guidewires without any disruption of nitinol wires.

CONCLUSIONS

Ho:YAG laser induced damage to endourologic tools is significantly higher compared with the impact of the FREDDY or the FLPD-laser. Because complete disruption of guidewires and stone extraction tools occurred, a safety clearance must be kept between the fiber tip and the endourologic tool during Ho:YAG stone disintegration. If disruption is intended, such as in the case of basket-retrieval problems, it can easily be performed with Ho:YAG irradiation.

Laser fragmentation of foreign bodies in the urinary tract: an in vitro study and clinical application

PURPOSE

Foreign bodies of the urinary tract represent a urologic emergency. First-line treatment is endoscopic removal, but this is often impeded by restricted space, especially in the urethra. We postulated that foreign objects could be fragmented by Holmium:YAG laser and investigated its effect on objects of varying composition.

METHODS

In a specially designed stage flushed with physiologic saline, medical and non-medical objects of differing composition and diameter were subjected to fragmentation by Holmium:YAG at powers of 18 and 30 W. In additional thermal experiments, 5,000 J was applied to differing volumes of 0.9% sodium chloride. Experiments were repeated ten times.

RESULTS

With one exception (16 Ch silicon catheter) all medical objects were fragmented (latex urinary catheter, ureteral stents, and guidewires). Of non-medical objects (wood, steel, copper, graphite, and nylon) only copper wire was not amenable to laser dissection. These in vitro results were applied in two patients who presented with a pencil (wood and graphite) in the urethra or bladder. After Holmium:YAG laser fragmentation, the pencil could be removed by forceps each.

CONCLUSION

Foreign objects in the urinary tract can be fragmented with a Holmium:YAG laser. When foreign bodies are too big for initial endoscopic extraction, the clinician should consider this technique as a reasonable and atraumatic option to avoid open surgery.

Ureteric guidewire damage by Holmium:YAG laser: preliminary results

Typically, guidewires are regularly used to provide access or act as a guide during laser lithotripsy. This may result in the tip of the fibre being in close proximity to the guidewire during the firing period and consequently, this could result in accidental damage to the guidewires during the procedure. To replicate this scenario, an experimental model was designed enabling accurate and reproducible positioning of the laser fibre relative to the guidewire. The guidewire was exposed to the laser energy for a range of typical settings used in the clinic. The results demonstrate that the guidewire is susceptible to laser energy damage, especially in close proximity to the fibre.

Use of Holmium:YAG laser to facilitate removal of intravesical foreign bodies

BACKGROUND AND PURPOSE

Foreign bodies in the bladder present a challenge to the urologist. Previously, endoscopic extraction, with or without perineal urethrotomy, or open cystotomy were the only treatment choices. We describe a novel use of the Ho:YAG laser for the removal of intravesical foreign bodies. We further tested the laser on objects that have been reported in the literature to necessitate open cystotomy to determine their suitability for endoscopic removal.

MATERIALS AND METHODS

The Ho:YAG laser is introduced through the cystoscope and used to cut large foreign bodies into a size that can be extracted through the urethra. We tested the Ho:YAG laser ex vivo on other objects that have been reported as intravesical foreign bodies.

RESULTS

We removed a large complex foreign body with the laser that would otherwise have necessitated open cystotomy. No injury or sequela was observed. Many commonly reported intravesical foreign objects seem amenable to similar treatment.

CONCLUSION

The Ho:YAG laser should be considered for use to facilitate removal of foreign bodies from the bladder.

Risk of collateral damage to endourologic tools by holmium:YAG laser energy

BACKGROUND AND PURPOSE

Today, the holmium:YAG laser is the gold standard in endourologic stone treatment because of its high efficacy. However, guidewires and stone-extraction tools often are close to the fiber and may be damaged accidentally by the laser. The aim of our study was to evaluate the duration of laser application required to disrupt wires at different energy settings.

MATERIALS AND METHODS

Two standard wires (0.035-inch guidewire and 0.025-inch hydrophilic Terumo wire) and two baskets (1.9F Nitinol tipless and 3F stone extraction) were investigated. We used a holmium:YAG laser (Auriga; Wavelight Laser Technologie AG, Erlangen, Germany) and two fibers (230 and 365 microm) at 800 and 2000 mJ and a 5-Hz pulse rate. The laser was brought into direct contact with the wires.

RESULTS

The average time required for transection was 55 to 103 seconds for a safety wire. The Terumo wire broke after 20 to 40 seconds of direct laser application; 15 to 34 seconds was required for a Dormia basket. Thin Nitinol basket wires were disrupted after only 1 to 4 seconds. One- and two-factorial variance analysis showed a high degree of significance (P < 0.0001) of the energy level and type of wire.

CONCLUSION

The disruption of stone-extraction tools occurs in a remarkably short time with laser exposure, especially in case of Nitinol baskets, whereas guidewires are more resistant. Attention should be paid to avoiding contact of laser energy with wires and baskets during stone fragmentation.

Case report: the stone-basket nidus

A 55-year-old man presented with intermittent right-flank pain 6 months after ureteroscopic stone extraction with holmium laser lithotripsy. A distal-ureteral stone was removed that contained fragments of a stone basket. Diligent inspection of endourologic accessories is critical to ensuring no fragments are left in patients, especially when a laser has been used.

Removal of urolume endoprosthesis using holmium:YAG laser

A potential complication of UroLume endoprosthesis is migration, which may necessitate removal of the stent. Stent removal may be associated with complications such as urethral injury, bleeding, and external sphincter trauma. We report a patient in whom a holmium:yttrium-aluminium-garnet (Ho:YAG) laser was used to cut the UroLume endoprosthesis into fragments, which led to easy and uneventful stent removal.

The broken stone basket: configuration and technique for removal

PURPOSE

We investigated the ease of breakage of endoscopic stone baskets with the holmium:yttrium-aluminum-garnet (YAG) laser and their resultant configuration. More importantly, possible safe methods of retrieval were evaluated.

MATERIALS AND METHODS

Endoscopic stone baskets from Bard (Platinum Class 2.4F Flat and 3.0F Helical Wire), Cook (3.2F Captura, 3.2F Atlas, 3.0F N-Circle, 4.5F N-Force), and Microvasive (2.4F Zero Tip, 3.0F Gemini, 3.0F Segura) were broken once using the holmium:YAG laser. The energy (kJ) required to break one of the wires was recorded. Configuration was documented using photographs. Baskets were disassembled and assessed for extraction through a 7F open-ended catheter, an 8F/10F set, and a 20F peel-away sheath.

RESULTS

Tipless baskets (N-Circle, Zero Tip) broke the easiest (range 0.02-0.03 kJ). Tipped baskets (Segura, Platinum Class Flat and Helical, Gemini, Captura, N-Force, Atlas) were more resistant, but all broke within the range (0.06-0.78 kJ) typically used for intracorporeal lithotripsy. Broken segments of wire tended to protrude outward, with tipless baskets having less change in configuration than tipped baskets. Tipless baskets could easily be pulled into any of the extracting devices, whereas tipped baskets could not.

CONCLUSIONS

Baskets break at typical holmium:YAG intracorporeal lithotripsy energy settings. Tipless baskets break easiest and assume a safer configuration. Tipless baskets are extracted easily through a 7F open-ended catheter, 8F/10F set, or 20F sheath, while tipped baskets are unable to be extracted through any of these.

Experience with the holmium laser as an endoscopic lithotrite

INTRODUCTION

Holmium laser lithotripsy represents an additional option in the management of urinary tract calculi. We report the results of a cohort of patients with ureteric and bladder calculi treated with this modality.

METHODS

Twenty-three patients underwent holmium laser lithotripsy to treat ureteric or bladder calculi. Power settings of 0.5 J to deliver 2.5-4.0 watts were used for the ureteric calculi, and up to 30 watts for the bladder calculi.

RESULTS

The mean ureteric stone size was 7.3 mm (range 4-10 mm). One stone was upper ureteric, seven were mid-ureter and nine were lower-ureter. Eighteen of the 19 patients with ureteric calculi were free of stones 28 days postoperatively. The remaining patient was clear by 12 weeks. All patients with bladder calculi were completely cleared of stones. There were no intraoperative complications.

DISCUSSION

Ureteric stone position can limit the use of extracorporeal shock wave lithotripsy due to imaging difficulties. Ureteric lithotripsy overcomes this problem. The holmium laser has proven to be safe and effective in clearing urinary stone burdens of a variety of sizes, sites and compositions in this cohort of patients.

Endoscopic lithotripsy with the holmium:YAG laser

BACKGROUND AND OBJECTIVE

The holmium:YAG (Ho:YAG) laser can be used not only for soft tissue but also for hard tissue such as urinary calculi. The objective of this study was to assess the usefulness of the Ho:YAG laser for endoscopic lithotripsy in patients with urinary tract stone. STUDY DESIGN/MATERIASL AND METHODS: Of 102 procedures performed among 96 patients, 88 were transurethral ureterolithotripsy (TUL), seven were percutaneous nephrolithotripsy, and seven were transurethral cystolithotripsy. Six patients had bilateral stones. The fragments were reduced as much as possible with the Ho:YAG laser.

RESULTS

The efficacy rate of the 102 lithotripsy procedures was 93%. With respect to the effect of TUL, the efficacy rates of 40 procedures for the proximal ureter, 18 procedures for the midureter, and 30 procedures for the distal ureter were 85%, 94%, and 100%, respectively.

CONCLUSION

The Ho:YAG laser produced a sufficiently strong lithotripsy force on all stones. The results of this study indicate that lithotripsy of urinary tract stones with the Ho:YAG laser can achieve a clinical outcome equivalent to or exceeding that of pulsed dye laser lithotripsy. The Ho:YAG laser is a multipurpose laser and thus is a cost effective and very useful means for endoscopic lithotripsy of urinary tract stones.