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

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).

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.

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).

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.